Miracle-dz/UniFAR-FTUs huggingface dataset:
Stellar Rotation in Young Clusters: The First 4 Million Years

To investigate what happens to angular momentum during the earliest observable phases of stellar evolution, we searched the literature for periods (P), projected rotational velocities (v sin i), and supporting data on K5–M2 stars (corresponding to masses 0.25–1 M⊙) from the Orion Nebula Cluster and environs, ρ Ophiuchi, TW Hydra, Taurus-Auriga, NGC 2264, Chamaeleon, Lupus, and η Chamaeleonis. We combine these measures of rotation with the stellar R (as determined from Lbol and Teff) to compare the data with two extreme cases: conservation of stellar angular velocity and conservation of stellar angular momentum. Analysis of the P data set suggests that the frequency distribution of periods among the youngest and oldest stars in the sample is indistinguishable, while the v sin i data set reveals a decrease in mean v sin i as a function of age. Both results suggest that a significant fraction of all pre–main-sequence (PMS) stars must evolve at nearly constant angular velocity during the first ∼3–5 Myr after they begin their evolution down the convective tracks. Hence, the angular momenta of a significant fraction of pre–main-sequence (PMS) stars must be tightly regulated during the first few million years after they first become observable. This result seems surprising at first glance, because observations of young main-sequence stars reveal a population (30%–40%) of rapidly rotating stars that must begin to spin up at ages t ≪ 5 Myr. To determine whether these apparently contradictory results are reconcilable, we use simple models along with our data set to place limits on (1) the fraction of PMS stars that must be regulated, and (2) the complementary fraction that could spin up as a function of time but escape statistical detection given the broad distribution of stellar rotation rates. These models include (1) instantaneous release at the stellar birthline of a given fraction of stars, with the remaining fraction regulated for 10 Myr; (2) all stars regulated initially, with the released fraction varying linearly with time, and timescales for release of half the stars varying from 0.5 to 5 Myr (i.e., all released by 1 to 10 Myr); and (3) a hybrid model that invokes assumptions (1) and (2). In all cases, we find that a modest population (30%–40%) of PMS stars could be released within the first 1 Myr and still produce period distributions statistically consistent with the observed data. This population is large enough to account for the rapid rotators observed among young main-sequence stars of comparable mass. The limits placed by our models on the fraction of regulated and released stars as a function of time are also consistent with the lifetime of accretion disks as inferred from near-IR excesses, and hence with the hypothesis that disk locking accounts for rotation regulation during early PMS phases.
Short-Circuit Destruction of Field-Stop-Structure Inslated Gate Bipolar Transistor

Numerical and experimental results of the field stop (FS) and lifetime control (LC) IGBT short-circuit characteristics using 4500 V-class devices are described. During the short-circuit condition, avalanche breakdown occurs along the base/FS layer interface. This is because the strength of the electric field becomes high due to the increase in the majority carrier concentration, which is larger than the impurity concentration in the base layer. The lower current gain in the device results in a higher electric field. It can be concluded that FS-IGBT has a narrower short circuit safety operating area (SCSOA) than other devices. Particularly, this phenomenon is easy to show on the high-voltage-class device, such as a 4.5 kV IGBT, because its impurity concentration in the base layer is low.
Tropical Squall Lines of the Arizona Monsoon

Abstract Squall lines possessing nearly all the characteristics of tropical squall lines occasionally develop during the summer monsoon over southern Arizona and northwestern Mexico. Initial thunderstorm formation is over the Continental Divide in the late afternoon and the systems become organized within a few hours. Satellite imagery, cloud-to-ground lightning strike data, and surface observations indicate the squall lines move from east to west or northeast to southwest by discrete propagation faster than the environmental flow at all levels below 20 kPa so that most of the anvil clouds lag behind. The synoptic-scale circulation is anomalous with a strong ridge located over the western United States and a deep trough located over the eastern United States. West to northwest winds are found in the boundary layer over southern Arizona and northwest Mexico while a deep layer of east winds are observed above. As a result most of the environmental wind shear is confined to the lowest 2.5 km above the ground.
STARE operations experience and its data quality control

The STARE instrument was the first to detect the transits of an extrasolar planet in 1999. To date it has performed one of the longest running searches for transits, being in nearly continous operations since July 2001 at Teide Observatory, Tenerife. We describe the instrumental setup and the scheme that is used for data acquisition, handling and analysis. To this end, we first review the conditions under which we obtained data suggestive of transits, and we then follow a chain of verification and follow-up measures, progressing from fairly simple ones of low cost and effort towards more involved ones, which may be needed to positively verify the existence of a true planetary transit. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Spontaneously broken de Sitter symmetry and the gravitational holonomy group

The local geometrical structure of general relativity is analyzed in detail from the standpoint of a formulation of gravity as a gauge theory of the de Sitter group SO(3,2). In order to reproduce the structure of the Einstein-Cartan theory, it is essential that the SO(3,2) gauge symmetry be spontaneously broken down to the Lorentz group. In the geometrical analysis of this spontaneously broken theory, the Goldstone field of the symmetry-breaking mechanism plays a central role, representing the coordinates of a point in an internal anti-de Sitter space where the motions induced by parallel transport across space-time take place. In order to establish the connection between the SO(3,2) gauge theory and the Einstein-Cartan theory, the gravitational vierbein and spin connection are derived from the original SO(3,2) gauge fields by passing over to a set of nonlinearly-transforming fields through a redefinition involving the Goldstone field. The original SO(3,2) gauge fields have a different but equally important role: they generate pseudotranslations and rotations in the internal anti-de Sitter space under a kind of parallel transport across space-time that is called ''development. '' Development maps curves in space-time into image curves in the internal space, and vector fields along the curves in space-time into imagemore » vector fields along the image curves. Considering development along infinitesimal closed curves in space-time leads to the proper interpretation of the effects of torsion and of curvature in terms of the nonclosure of image curves and of the rotation of image vectors with respect to their original values. « less
Critical scaling and percolation in manganite films

In this work the critical behaviour of films of La0.7Ba0. 3MnO3, La0.7Sr0. 3MnO3, La0.7Ca0. 3MnO3 and (LaMn)1-δO3 is studied. Apart from the La0.7Ca0. 3MnO3 film, each of these manganite films shows a continuous phase transition with mean-field critical exponents. The analysis of the critical amplitudes indicates the formation of spin polarons. The zero-field resistivity of the La0.7Ca0. 3MnO3 film is consistent with a model of percolative phase separation.
A new approach to evaluate the cavitation erosion power

The dynamic response of various materials exposed to liquid jet and pressure wave impacts was simulated making use of an elastoplastic solid model. Numerical pit profiles were compared to experimental ones produced in test materials by the cavitation of water, mercury, or sodium. It was found that a high pressure wave emission was the main factor contributing to the observed cavitation damage. A parametric study concerning the pressure wave phenomenon was proposed and some similarity laws were obtained. By using these laws, the corresponding impact hydrodynamic parameters can be deduced from the pit geometric characteristics and the material properties. Based on that study, histograms concerning impact hydrodynamic parameters were plotted as a function of impact number and/or pit eroded volume. The influence of the mean flow velocity, the geometric scale, the fluid characteristics, and the material properties on the flow aggressivity could be evaluated during the cavitation incubation period.
An additive group utility for a fund manager

The additive utility formula developed by Harsanyi specifies how a rational ethical individual acting on behalf of other people ought to behave. Unfortunately the formula is not invariant to arbitrary utility transformations and hence requires interpersonal comparisons of utility. Many economists have also attacked the formula on ethical grounds. This paper transplants the Harsanyi paradigm to a new context: that of fund management. We add three further axioms to the Harsanyi argument and deduce the weighted group utility formula with each individual's weight equal to the inverse of the marginal utility of his investment in the fund. These weights make our formula invariant to arbitrary utility transformations which eliminates the problem of interpersonal comparisons of utility. We also explore a number of other properties of this group utility function.
Comparison of estimation methods for the Weibull distribution

Weibull distributions have received wide ranging applications in many areas including reliability, hydrology and communication systems. Many estimation methods have been proposed for Weibull distributions. But there has not been a comprehensive comparison of these estimation methods. Most studies have focused on comparing the maximum likelihood estimation (MLE) with one of the other approaches. In this paper, we first propose an L-moment estimator for the Weibull distribution. Then, a comprehensive comparison is made of the following methods: the method of maximum likelihood estimation (MLE), the method of logarithmic moments, the percentile method, the method of moments and the method of L-moments.
PRIME SPECTRUM AND AUTOMORPHISMS FOR 2×2 JORDANIAN MATRICES

ABSTRACT This paper is devoted to some ring theoretic properties of the jordanian deformation of the algebra of regular functions on the matrices with coefficients in an algebraically closed field of characteristic zero, and of the associated factor algebra . We prove in particular that the prime spectrum of is the disjoint union of five components, each of which being homeomorphic to the spectrum of a commutative (possibly localised) polynomial ring. So we can give an explicit description of the prime spectrum of , and check that any prime factor of satisfies the Gelfand-Kirillov property. Then we study the automorphism groups of the algebras and and prove that they are generated by linear automorphisms and exponentials of locally nilpotent derivations.
Band and Localized States in Finite and Infinite Crystals

The connection of symmetry groups, their irreducible and band representations for the models of finite and infinite crystals is considered in detail. The relation between localized (electronic and vibrational) states of finite and infinite crystals is studied on models. It is found that the Wannier states of an infinite crystal are reproduced well by Wannier states of cyclic systems with size slightly exceeding the region of their localization.
Parametric study and temperature sensitivity of microstrip antennas using an improved linear transmission line model

An improved linear transmission line (LTL) model has been developed after incorporating several modifications in the reported linear transmission line model for analyzing arbitrarily shaped microstrip antennas (MSAs), which should be symmetrical with respect to the feed axis. Simulations have been carried out for rectangular, circular, and equilateral triangular MSAs and the results are in good agreement with reported results. A parametric study for these MSAs has also been performed. A study of the temperature sensitivity for rectangular MSAs for different types of substrates has been carried out. An MSA utilizing a substrate with a lower dielectric constant and thermal coefficient is less sensitive to temperature variations.
On the role of the losses in metamaterials

Contrarily to classic Right-Handed Materials (RHMs), the role of losses is crucial for composite materials called metamaterials such as Ultra-refractive Right-Handed Materials (URHMs) and Left-Handed Materials (LHMs). As the loss-free case for a metamaterial is not stable, a small variation of losses can drastically modify the expected properties of such a material. Thus, it is important to understand how the input of lossy term affects URHM and LHM aspects, and also to define, for each of them, the tolerance level for which the interesting metamaterial properties are still valid. The role of losses is investigated analytically and numerically, a full study about the action of the losses on all the properties is done. It is shown that those properties almost completely disappear for an LHM slab with loss tangent over 0.01, which at optical frequencies corresponds to a good material.
First observations of the PMSE overshoot effect and its use for investigating the conditions in the summer mesosphere

We report from the first campaign, with the EISCAT radars and heating facility, which looked for a proposed new PMSE overshoot effect resulting when PMSE is being affected by a specific cycling of artificial electron heating. The overshoot was predicted to appear after unaffected PMSE dusty plasma had been acted upon, for a comparatively short time, by the EISCAT Heating facility. We show model results and observational examples of the overshoot effect. For the overshoot to be clearly observable, a long relaxation time after the heater is switched off is necessary to get the dust charges back to those of dust unaffected by the heated electrons or, to bring unaffected PMSE dusty plasma into the radar beams by horizontal wind transport. The overshoot characteristic curve (OCC) contain a substantial amount of information on the conditions during PMSE and must lead to new possibilities in the study of PMSE and the conditions close to the summer mesopause.
A Novel Planar Printed Array Antenna with SRR Slots

Metamaterials, which are composite materials constructed usually by periodic and artificial resonant structures, have been widely utilized in many fields including the antenna design. Quite different from popular methods of embedding an antenna inside a metamaterial or placing metamaterial plates in front of an antenna, this work explores using a metamaterial structure, the periodic split-ring resonator (SRR), to design radiation slots in a printed array antenna for high gain. A proposed array with 4×4 slots and working at 5.8 GHz has been automated designed by using the Genetic Algorithm (GA) in conjunction with the parallel computation on a cluster. Both results of numerical simulations and measurements demonstrate, in comparison with an array using conventional rectangular slots, that the proposed array with SRR slots possesses almost the same impedance bandwidth, side-lobe and cross polarization level, but the gain is improved from 18.7 dBi to 19.6 dBi.
A New Procedure for Optimization of a Class of Linear Time-Varying Dynamic Systems

This paper deals with optimization of a class of linear time-varying dynamic systems with n states and m control inputs commanded to move between two fixed states in a prescribed final time. Using a conventional procedure with Lagrange multipliers, it is well known that the optimal solution must satisfy 2n first-order linear differential equations in the state and Lagrange multiplier variables. Due to the specific nature of boundary conditions with states given at the two end times, the two-point boundary value problem must be solved iteratively using shooting methods, that is, there is no closed-form quick procedure to obtain the solution of the problem. In this paper, a new procedure for dynamic optimization of this problem is presented that does not use Lagrange multipliers. In this new procedure, it is shown that for a dynamic system with n = pm, where p is an integer, the optimal solution must satisfy m 2p-order differential equations. Due to the absence of Lagrange multipliers, the higher order differential equations can be solved efficiently using classical weighted residual methods.
A comparison of optical and VLA rotation curves for Virgo spirals

From high-resolution optical CCD spectra, were formed rotation curves for eight spiral galaxies in the Virgo Cluster (NGC 4178, 4237, 4388, 4501, 4568, 4569, 4579, and 4654). A comparison with rotation curves formed from VLA observations shows excellent agreement for the galaxies abserved at 21 cm with 15 arcsec resolution. However, for galaxies observed at 45 arcsec resolution, the 21-cm velocities are lower than the optical velocities at virtually all radii covered by the optical velocities. The initial rise of the rotation curve is often well matched by the low-resolution observations, an unexpected result. A computer program that models the VLA observations confirms that observations at low spatial and velocity resolution will produce low rotation velocities, especially in the region of the turnover of the rotation curve. 7 refs.
Internal Schottky barriers in semiconductors

We discuss the effect on the electrical conductivity of a semiconductor if small metal inclusions are formed within the bulk of the semiconductor where the metal to semiconductor contact is a rectifying one. We find that the depletion layers formed inside the material can dominate the conduction process and give rise to conditions similar to that of a highly compensated semiconductor with highly variable activation energy. Some of the predictions of the model are compared to observed facts in cuprous oxide and are shown to be consistent with observation. The expected behaviour of a semiconductor with internal injecting contacts is also briefly discussed.
Measurement of Expected Nucleation Precursor Species and 3–500-nm Diameter Particles at Mauna Loa Observatory, Hawaii

Abstract Atmospheric measurements of expected homogeneous nucleation precursors and aerosols were made at the Mauna Loa Observatory, Hawaii, from 28 June to 27 July 1992. Large molecular clusters and gas phase species including sulfuric acid (H2SO4), methane sulfonic acid (MSA), and OH were measured with a mass spectrometer. Aerosol measurements consisted of ultrafine particle concentrations (∼3–4 nm diameter) and fine particle size distributions (15–500 nm diameter). The altitude of the observatory (average pressure 680 mb) and the presence of mountain–valley winds permitted sampling of both up- and downslope air. Downslope air was found to have the highest concentrations of MSA but low ultrafine concentrations, whereas, upslope air had the highest H2SO4 and ultrafine concentrations. Episodes of substantial increase in ultrafine particles were observed during periods of rapid increase in H2SO4 concentrations. Total aerosol surface area and H2SO4 concentrations had the strongest influence on ultrafine par.
The Heliospheric Magnetic Field

The heliospheric magnetic field (HMF) is the extension of the coronal magnetic field carried out into the solar system by the solar wind. It is the means by which the Sun interacts with planetary magnetospheres and channels charged particles propagating through the heliosphere. As the HMF remains rooted at the solar photosphere as the Sun rotates, the large-scale HMF traces out an Archimedean spiral. This pattern is distorted by the interaction of fast and slow solar wind streams, as well as the interplanetary manifestations of transient solar eruptions called coronal mass ejections. On the smaller scale, the HMF exhibits an array of waves, discontinuities, and turbulence, which give hints to the solar wind formation process. This review aims to summarise observations and theory of the small- and large-scale structure of the HMF. Solar-cycle and cycle-to-cycle evolution of the HMF is discussed in terms of recent spacecraft observations and pre-spaceage proxies for the HMF in geomagnetic and galactic cosmic ray records.
Fast quantitative microwave imaging with resolvent kernel extracted from measurements

A quantitative imaging method is proposed based on microwave measurements where a direct inversion in real space is employed. The electrical properties of penetrable objects are reconstructed using a resolvent kernel in the forward model, which is extracted from calibration measurements. These measurements are performed on two known objects: the reference object (RO) representing the scatterer-free measurement and the calibration object representing a small scatterer embedded in the RO. Since the method does not need analytical or numerical approximations of the forward model, it is particularly valuable in short-range imaging, where analytical models of the incident field do not exist while the fidelity of the simulation models is often inadequate. The experimentally determined resolvent kernel inherently includes the particulars of the measurement setup, including all transmitting and receiving antennas. The inversion is fast, allowing for quasi-real-time image reconstruction. The proposed technique is demonstrated and validated through examples using simulated and experimental data. Its performance with noisy data is also examined. The concept of experimentally determined resolvent kernel in the forward model may be valuable in other imaging modalities such as ultrasound, photonic imaging, electrical-impedance tomography, etc.
SWICS/Ulysses observations: The three‐dimensional structure of the heliosphere in the declining/minimum phase of the solar cycle

The ESA/NASA spacecraft Ulysses provides the first in‐situ observation of the solar wind at high solar latitudes. Data obtained with the Solar Wind Ion Composition Spectrometer (SWICS) during the first orbit of Ulysses around the Sun can be used to obtain a global view of the solar wind pattern within the heliosphere during the declining/minimum phase of the solar activity cycle. This provides information on the solar corona, specifically on any latitudinal variation of coronal parameters as far as they play a role in the solar wind acceleration process. The measurements show: The 3‐dim. distribution of the solar wind appears as a pattern of basically two states. The fast solar wind with speeds of about 750 km/s emanating from the polar coronal holes dominates the heliosphere. The slow solar wind from the streamer belts is restricted to a region of about +/−20° around the heliographic equator. The boundary between the two states of the solar wind is sharply defined. The coronal hole streams are remarkably stable and homogeneous on a larger scale. The two independent coronal holes are similar in terms of average speed and spatial extent. In both coronal holes a gradual increase (≤10%) of speed with solar latitude is observed.
Planar microoptomechanical waveguide switches

Planar micromechanical waveguide switches based on lateral deflection of a cantilever beam are presented. Two material systems have been used: a GaAs-AlGaAs structure with integrated waveguides and a silicon-on-insulator (SOI), with postprocessed polymeric waveguides. The switches are characterized by low actuation voltage (3-20 V), short switching times (32-200 /spl mu/s), and low crosstalk (< -30 dB).