Miracle-dz/UniFAR-FTUs huggingface dataset:
Nonlinear trapping simulations for helicon plasma sources

Summary form only given, as follows. The nonlinear trapping process is an important effect which may contribute to the extraordinary high wave damping rate of helicon sources. We are developing a numerical simulation method and code to study nonlinear phenomena in plasmas with complex wave structure. An open system with a steady-state initial distribution function is considered. In the case of low density (n<10/sup 11//cm/sup 3/) where collision effects can be neglected, the distribution function as a function of time and space is obtained by solving the motion equation and tracing particle trajectories back to the starting point. Our simulation results for a sinusoidal wave field show that trapped electrons with wave-particle phase confined within a range of phase less than 2/spl pi/ appear as the wave field intensity increases, and the distribution function shows bunching of fast particles around 40 eV at an E/sub z/ field intensity of 100 V/m. We are studying the effects of a wave number spectrum, a frequency spectrum, and field components including /spl mu//spl nabla//sub z/B/sub z/ and E/sub /spl perp// in addition to the electrostatic E/sub z/ on the nonlinear trapping process. The modelling of wave fields are based on the simulation results from our ANTENA II and MAXEB codes. We will also carry out the simulation utilizing MAGIC particle-in-cell code and comparison between these two approaches will be discussed. We will at the same time compare our simulation results with current experiments being carried out on our helicon experimental facility.
Endfire tapered slot antennas on dielectric substrates

Endfire tapered slot antennas are suitable for many integrated circuit applications, imaging and phased arrays. We report on an investigation of single elements of such antennas, including slots which are exponentially tapered (Vivaldi), linearly tapered (LTSA) and constant width (CWSA). For antennas of all types, a good general agreement is obtained for curves of beamwidth versus length, normalized to wavelength, when one compares the data with that for traveling-wave antennas published by Zucker. An important condition for this agreement is that the effective dielectric thickness, defined in the text, is in a certain optimum range. This condition is qualitatively explained in terms of the theory for traveling-wave antennas.
A central limit theorem for two-dimensional random walks in random sceneries

Let $S_n$, $n\in\bold N$, be a recurrent random walk on ${\bold Z}^2$ $(S_0=0)$ and let $\xi(\alpha)$, $\alpha\in{\bold Z}^2$, be i.i. d. $\bold R$-valued centered random variables. It is shown that $\sum^n_{i=1}\xi(S_i)/ \sqrt{n\log n}$ satisfies a central limit theorem. A functional version is also presented.
Photometric determination of facular contrasts near the solar disk center

Pairs of simultaneous digital photometric images of several solar active regions made with 3-A effective bandpasses in the CA II line at 8662 A have been analyzed. Images were obtained in 1984 with the 28-cm San Fernando Observatory solar telescope. After correction for bolometric and stray light effects, a continuum facular contrast at the disk center of 0.74 + or - 0.11 percent is found which remains roughly constant from the disk center out to r = 0.45 solar radii before increasing. These results demonstrate an increase of 10-20 percent over previous estimates of the contribution of faculae to solar luminosity fluctuations. 31 references.
Cold outflows, energetic winds, and enigmatic jets around young stellar objects

It has long been suspected that young stars, especially those of low-to­ intermediate mass, experience vigorous episodes of mass loss during their evolution to the main sequence. However, the magnitude and significance of such episodes for early stellar evolution have only recently become apparent. As a result of a series of remarkable and' exciting observational discoveries made across the electromagnetic spectrum during the last five years, a new stage of early stellar evolution of unanticipated astrophysical importance has been identified. It is now generally believed that during the earliest stages of evolution, most, if not all, stars undergo a phase of very energetic mass ejection, frequently characterized by the occurrence of massive bipolar outflows of cold molecular gas. These outflows appear to be driven by strong stellar winds, whose other notable manifestations include rapidly moving Herbig-Haro (HH) objects, high-velocity water maser sources, shock-excited molecular hydrogen emission regions, and optically visible jets appearing to emanate directly from the immediate circum stellar environs of the young driving stars themselves. The kinetic energies inferred for such outflowing gas are enormous (e.g. 1043_1047 erg)
Total electron scattering cross sections for methanol and ethanol at intermediate energies

Absolute total cross section (TCS) measurements of electron scattering from gaseous methanol and ethanol molecules are reported for impact energies from 60 to 500 eV, using the linear transmission method. The attenuation of intensity of a collimated electron beam through the target volume is used to determine the absolute TCS for a given impact energy, using the Beer–Lambert law to first approximation. Besides these experimental measurements, we have also determined TCS using the additivity rule.
Infinite dimensional exponential attractors for a non–autonomous reaction–diffusion system

In this article, we give a construction of exponential attractors that is valid for general translation–compact non–autonomous systems. Since they are generally infinite dimensional, we replace, compared with the standard definition, the condition of finite fractal dimensionality of exponential attractors by requiring that their epsilon–entropy have the same form as that of the uniform attractor. As an example, we prove the existence of an (infinite dimensional) exponential attractor for a reaction–diffusion system.
Some identities for the Glasser transform and their applications

In the present paper we consider a new integral transform, denoted by $\mathcal{G}_{\nu}$, which may be regarded as a generalization of the well-known transform due to Glasser. Many identities involving this transform are given. By making use of these identities, a number of new Parseval--Goldstein type identities are obtained for these and many other well-known integral transforms. The identities proven in this paper are shown to give rise to useful corollaries for evaluating infinite integrals of special functions. Some examples are also given as illustrations of the results presented here.
A physical model for earthquakes: 3. Thermodynamical approach and its relation to nonclassical theories of nucleation

If a theory of earthquakes, sliding, and frictional slip is to have general validity, it should ideally arise out of fundamental thermodynamical considerations. We construct just such a theory using the principle that physical systems, including fault systems, tend toward a state of minimal Helmholtz free energy. If the system is not in a state of minimal free energy, thermodynamic forces arise which drive the system toward a minimum. Allowed minima in the free energy may be either global, representing static (absolute) equilibrium, or local, representing states of metastable equilibrium. Within the context of this theory, fault systems are understood to be in states of metastable equilibrium, kept there by action of the far-field plate-driving stresses, which continually keep the far-field displacement ahead of the state of slip on the fault. Earthquakes therefore represent a sudden decay of the fault system from a state of metastable equilibrium to a state closer to static (absolute) equilibrium. The major difficulty is the formulation of an appropriate expression for the Helmholtz free energy of the system. The solution of this problem is facilitated by starting from classical nucleation theory, which was first formulated by Gibbs for general thermodynamical systems and later applied by Griffith for the specific case of the fracture of solids. Much more recently, significant advances have been made in understanding the physics of nucleation. In accordance with these ideas, in this paper the free energy is therefore written as a sum of two terms: one which describes the elastic potential energy contained by the solid (i.e., the internal energy) and one which describes the energy necessary to rupture and/or reconnect atomic and cohesive bonds (i.e., an entropy term). The former term describes thermodynamically reversible processes, and the latter more generally describes thermodynamically irreversible processes. In the Griffith theory of fracture the latter term is a surface energy term, since the creation of an element of surface requires the rupture of atomic or cohesive bonds. Together, these two terms most generally define a nonclassical free energy functional, which, when minimized, leads to two equations. The first equation is the classical equation obtained by Gibbs and Griffith, which relates the size of the slip region to the applied field. The second equation is a nonclassical Euler-Lagrange equation, which can be solved to obtain the distribution of slip on the slip surface. In addition to developing these ideas, it is shown that the assumption of thermodynamic irreversibility, that is, nonnegative entropy production, leads to a specific requirement for the kinetic growth of slip and the growth of the slip region. A discussion is then given of how these ideas relate to the kind of hysteresis effects commonly observed in frictional experiments and of how these effects may be interpreted in terms of the physics of states of metastable equilibrium.
LATERAL OFFSET OF THE CORONAL MASS EJECTIONS FROM THE X-FLARE OF 2006 DECEMBER 13 AND ITS TWO PRECURSOR ERUPTIONS

Two GOES sub-C-class precursor eruptions occurred within ∼10 hr prior to and from the same active region as the 2006 December 13 X4.3-class flare. Each eruption generated a coronal mass ejection (CME) with center laterally far offset (≳ 45°) from the co-produced bright flare. Explaining such CME-to-flare lateral offsets in terms of the standard model for solar eruptions has been controversial. Using Hinode/X-Ray Telescope (XRT) and EUV Imaging Spectrometer (EIS) data, and Solar and Heliospheric Observatory (SOHO)/Large Angle and Spectrometric Coronagraph (LASCO) and Michelson Doppler Imager (MDI) data, we find or infer the following. (1) The first precursor was a “magnetic-arch-blowout” event, where an initial standard-model eruption of the active region's core field blew out a lobe on one side of the active region's field. (2) The second precursor began similarly, but the core-field eruption stalled in the side-lobe field, with the side-lobe field erupting ∼1 hr later to make the CME either by finally being blown out or by destabilizing and undergoing a standard-model eruption. (3) The third eruption, the X-flare event, blew out side lobes on both sides of the active region and clearly displayed characteristics of the standard model. (4) The two precursors were offset due in part to the CME originating from a side-lobe coronal arcade that was offset from the active region's core. The main eruption (and to some extent probably the precursor eruptions) was offset primarily because it pushed against the field of the large sunspot as it escaped outward. (5) All three CMEs were plausibly produced by a suitable version of the standard model.
A theoretical treatment of the absorption spectra of all-benzenoid hydrocarbons

The class of compounds known as the all-benzenoid polycyclic aromatic hydrocarbons (AB- PAHs) are treated with time-dependent density functional theory (TDDFT) and a modified Huckel theory to determine how large an ABPAH must be before it is found to absorb strongly in the visible region that corresponds to the bluest of the diffuse interstellar bands (DIBs). The first six ABPAHs are treated with TDDFT using the B3LYP functional to determine their excitation energies. A two-parameter Huckel theory is adopted to deal with those systems too large to be addressed with TDDFT. The transitions are calculated and fitted to experimental data. An ABPAH system with 84 carbons and 14 all-benzenoid rings is found to be the first carrier to absorb strongly in the region where DIBs are observed.
Condition for the general ideal boundary

The electromagnetic ideal boundary is defined as a surface on which the complex Poynting vector has no normal component. Examples of such boundaries are the perfect electric and magnetic boundaries, as well as the soft-and-hard surface with its recent generalization. In the present study, the general ideal-boundary condition is introduced, and basic properties of plane-wave reflection from a planar boundary are studied in terms of normally and obliquely incident plane waves. It is seen that, in the general case, an incident wave is reflected in two directions. A special self-dual ideal planar boundary has the interesting property of being a perfect back-reflector for a plane wave incident from any direction. © 2000 John Wiley & Sons, Inc. Microwave Opt Technol Lett 26: 61–64, 2000.
Effect of nanoparticles on charge transport in nanofluid-impregnated pressboard

Transformer pressboard impregnated in mineral oil modified by nanoparticles (nanofluid) exhibits substantially higher AC and DC breakdown voltage than that of the pure oil-impregnated pressboard (OP). Charge transport and decay characteristics of both pressboards were measured by pulse electroacoustic technique. It reveals that nanofluid-impregnated pressboard (NP) has a more uniform internal electric field and a higher charge decay rate compared to OP, which is caused by an increase of shallow trap density in NP related to the difference of internal structures, based on the test results of thermally stimulated current and Fourier transformed infra-red spectroscopy.
Strange Attractors: Creating Patterns in Chaos

The moment came one winter day 1961 at MIT. Lorenz was running a climate model consisting of twelve differential equations representing climate parameters when he decided to reexamine one the run’s sequences. From printout he took conditions from a mid-point in the model run and reinitiated the calculations, making only one slight change: The original inputs had six decimal-digits, and Lorenz, to save time and space, rounded them to three for the second run. He quite reasonably expected that his second run would precisely match hiss first, but it didn’t. It was, in fact, almost precisely the same at the beginning, but then the second run diverged radically, bearing no resemblance to its mathematical parent. Clear that something was wrong, Lorenz first suspected a hardware problem, but there nothing amiss with his Royal McBee computer’s vacuum tubes. Then Lorenz realized the truth. The rounding of the initial inputs—a tiny change in initial values—had produced wildly divergent results.
Structural and transport properties of thermally evaporated nickel phthalocyanine thin films

X-ray diffraction patterns of NiPc in powder form show that it has a β-form with monoclinic structure. The thermal evaporation of NiPc led to α-polycrystalline films orientated preferentially to the (001) plane with an amorphous background. After annealing at 573 K for 2 h, a mixture of α- and β-phases was formed, while the conversion into β-NiPc is completed at 623 K. The dark electrical resistivity has been measured on NiPc films in the temperature range 298–423 K. Two activation energies ΔE1 = 0.12 eV and ΔE2 = 0.76 eV were obtained. The thermal activation energy ΔE1 is associated with impurity conduction and ΔE2 is associated with intrinsic conduction. Thermoelectric power measurement proved that NiPc films are p-type. The thermoelectric power curves also exhibit two different regions corresponding to extrinsic and intrinsic conductions. Room temperature J–V measurements show a linear ohmic dependence at low voltages, followed by SCLC at higher voltage levels, dominated by an exponential distribution of traps with total trap concentration of 2.79 × 1022 m−3.
Theoretical Modeling of the Thermal State of Accreting White Dwarfs Undergoing Classical Nova Cycles

White dwarfs (WDs) experience a thermal renaissance when they receive mass from a stellar companion in a binary. For accretion rates of less than 10-8 M☉ yr-1, the freshly accumulated hydrogen/helium envelope ignites in a thermally unstable manner that results in a classical nova (CN) outburst and ejection of material. We have undertaken a theoretical study of the impact of the accumulating envelope on the thermal state of the underlying WD. This has allowed us to find the equilibrium WD core temperatures (Tc), the CN ignition masses (Mign), and the thermal luminosities for WDs accreting at rates of 10-11 to 10-8 M☉ yr-1. These accretion rates are most appropriate for WDs in cataclysmic variables (CVs) of Porb ≲ 7 hr, many of which accrete sporadically as dwarf novae. We have included 3He in the accreted material at levels appropriate for CVs and find that it significantly modifies the CN ignition mass. We compare our results with several others from the CN literature and find that the inclusion of 3He leads to lower values of Mign for ⟨⟩ ≳ 10-10 M☉ yr-1 and that for ⟨⟩ values below this the particular author's assumption concerning Tc, which we calculate consistently, is a determining factor. Initial comparisons of our CN ignition masses with measured ejected masses find reasonable agreement and point to ejection of material comparable to that accreted.
Extended Models for Transitional Rough Wall Boundary Layers With Heat Transfer—Part I: Model Formulations

Two extended models for the calculation of rough wall transitional boundary layers with heat transfer are presented. Both models comprise a new transition onset correlation, which accounts for the effects of roughness height and density, turbulence intensity, and wall curvature. In the transition region, an intermittency equation suitable for rough wall boundary layers is used to blend between the laminar and fully turbulent states. Finally two different submodels for the fully turbulent boundary layer complete the two models. In the first model, termed KS-TLK-T in this paper, a sand roughness approach from Durbin et al. (2001, "Rough Wall Modification of Two Layer k-e , " ASME J. Fluids Eng., 123, pp. 16―21), which builds upon a two-layer k-e-turbulence model, is used for this purpose. The second model, the so-called DEM-TLV-T model, makes use of the discrete-element roughness approach, which was recently combined with a two-layer k-e-turbulence model by the present authors. The discrete-element model will be formulated in a new way, suitable for randomly rough topographies. Part I of the paper will provide detailed model formulations as well as a description of the database used for developing the new transition onset correlation. Part II contains a comprehensive validation of the two models, using a variety of test cases with transitional and fully turbulent boundary layers. The validation focuses on heat transfer calculations on both the suction and the pressure side of modern turbine airfoils. Test cases include extensive experimental investigations on a high-pressure turbine vane with varying surface roughness and turbulence intensity, recently published by the current authors as well as new experimental data from a low-pressure turbine vane. In the majority of cases, the predictions from both models are in good agreement with the experimental data.
Directivity Enhancement of Double-Slot Antennas by a Woodpile Electromagnetic Bandgap

Abstract Resonator antennas made from simple radiating devices placed between a woodpile and a ground plane are studied. A woodpile is a dielectric three-dimensional electromagnetic bandgap material that presents large stop-bands. A woodpile superstrate and a metallic plane, placed at an appropriate distance from each other, are equivalent to a woodpile cavity, the transmission response of which presents peaks inside the bandgaps. This property can be exploited to obtain highly directive radiators from low-directivity antennas. The cavity is fed by a double-slot antenna. The role of the permittivity of the constituent material of the rods is investigated. An evaluation of the bandwidth is performed for the directivity enhancement of the studied antennas, and the role of the woodpile covering area is pointed out.
Noise reduction for low-dose helical CT by 3D penalized weighted least-squares sinogram smoothing

Helical computed tomography (HCT) has several advantages over conventional step-and-shoot CT for imaging a relatively large object, especially for dynamic studies. However, HCT may increase X-ray exposure significantly to the patient. This work aims to reduce the radiation by lowering the X-ray tube current (mA) and filtering the low-mA (or dose) sinogram noise. Based on the noise properties of HCT sinogram, a three-dimensional (3D) penalized weighted least-squares (PWLS) objective function was constructed and an optimal sinogram was estimated by minimizing the objective function. To consider the difference of signal correlation among different direction of the HCT sinogram, an anisotropic Markov random filed (MRF) Gibbs function was designed as the penalty. The minimization of the objection function was performed by iterative Gauss-Seidel updating strategy. The effectiveness of the 3D-PWLS sinogram smoothing for low-dose HCT was demonstrated by a 3D Shepp-Logan head phantom study. Comparison studies with our previously developed KL domain PWLS sinogram smoothing algorithm indicate that the KL+2D-PWLS algorithm shows better performance on in-plane noise-resolution trade-off while the 3D-PLWS shows better performance on z-axis noise-resolution trade-off. Receiver operating characteristic (ROC) studies by using channelized Hotelling observer (CHO) shows that 3D-PWLS and KL+2DPWLS algorithms have similar performance on detectability in low-contrast environment.