Miracle-dz/UniFAR-FTUs huggingface dataset:
The effect of diamagnetic drift on the boundary conditions in tokamak scrape-off layers and the distribution of plasma fluxes near the target

The standard model for the two-dimensional simulation of the scrape-off layer (SOL) in the divertor is based on the equations for anomalous cross-field particle and energy transport and classical parallel transport. Recently, it has been complemented by the fluid equations of Braginskii to include all classical fluxes in a self-consistent way. The main physical effect of introducing classical fluxes is the appearance of two new terms-an electrical E*B drift and a diamagnetic B* Del P drift, as well as B* Del T contributions to the energy transport. Although the new models provide an adequate consideration of all the classical fluxes inside the plasma, a mistake has typically been made in the literature in formulating the new boundary conditions. The poloidal component of the B* Del Pi drift, existing inside the plasma, is assumed to continue through to the target surface, thus altering the Bohm criterion. Likewise, the poloidal current due to the B* Del (Pi+Pe) term is assumed to reach the surface, changing the surface electric potential drop. In this paper we demonstrate, however, that the diamagnetic fluxes in the whole plasma, including the SOL region, in their major part can be represented by the curl of a vector and, therefore, are self-terminating. We have made a detailed analysis of the distribution of plasma pressure and fluxes at the boundary between the plasma and the surface, encompassing the magnetic presheath and Debye sheath layers. After entering the presheath entrance, the poloidal component of the diamagnetic flux is diverted in the direction along the material surface due to the sharp pressure gradient in the presheath region. This creates boundary drift flows along the surface. Because of that conversion of the poloidal diamagnetic fluxes into boundary fluxes they do not deliver particles and current to the surface and therefore must not be included in the modified boundary conditions. Kinetic analysis of the distribution of the fluxes near the target also reveals an additional ExB drift in the radial direction, which mainly affects the ion motion in the magnetic presheath and Debye sheath layers. This drift is expected to shift the density profile of the plasma near the target in the radial direction a distance of the order of the ion poloidal Larmor radius.
Slope stability analyses for materials with a non-linear failure envelope

Upper bound techniques are used to analyse the stability of slopes of material failing according to a non-linear failure criterion, such as closely jointed rocks. The global, extremal nature of upper bound calculations is discussed, as is the inverse use of such procedures for obtaining safe lower bound estimates for material strength properties in back analyses. Specific results are presented for the material model proposed by hoek and brown. (Author/TRRL)
Particle segregation in monodisperse sheared suspensions

It has been known for a long time that many mixtures of granular materials tend to segregate when tumbled in a rotating horizontal cylinder, with the different components separating into bands of relatively pure single concentration along the rotational axis [Mixing of Solids, Advances in Chemical Eng., edited by T. B. Drew and J. W. Hoopes (Academic Press, New York, 1952), Vol. 2, p. 211]. Here we report a phenomenon that seems to be analogous, but in suspensions of monodisperse neutrally buoyant spherical particles in a Newtonian liquid medium being sheared in a partially filled horizontal Couette device in which the suspension separates itself into alternating regions of high and low particle concentration along the length of the tube. The experiment is mostly qualitative, the aim at this stage being primarily to provide photographic evidence of a curious and as yet unexplained phenomenon.
Femtosecond laser blackening of platinum

Using a femtosecond laser processing technique, we produce the black platinum with absorptance of about 95% over a broad wavelength range from ultraviolet to infrared. From scanning electron microscopy and energy dispersive x-ray spectroscopy studies, we find that the enhanced absorption of the black metal is due to a variety of nano- and microscale surface structures. Using a unique calorimetry technique, we perform a shot-to-shot comparison study of the metal absorption change in air and vacuum. Our study shows that the blackening process for platinum is more efficient in vacuum.
The functional determinant of a four-dimensional boundary value problem

Working on four-dimensional manifolds with boundary, we consider, elliptic boundary value problems (A, B), A being the interior and B the boundary operator. These problems (A, B) should be valued in a tensorspinor bundle; should depend in a universal way on a Riemannian metric g and be formally selfadjoint; should behave in an appropriate way under conformai change g —> Q2g , Í2 a smooth positive function; and the leading symbol of A should be positive definite. We view the functional determinant det Aß of such a problem as a functional on a conformai class {0.2g} , and develop a formula for the quotient of the determinant at Cl2g by that at g . (Analogous formulas are known to be intimately related to physical string theories in dimension two, and to sharp inequalities of borderline Sobolev embedding and Moser-Trudinger types for the boundariless case in even dimensions.) When the determinant in a background metric go is explicitly computable, the result is a formula for the determinant at each metric Si2g0 (not just a quotient of determinants). For example, we compute the functional determinants of the Dirichlet and Robin (conformally covariant Neumann) problems for the Laplacian in the ball B4 , using our general quotient formulas in the case of the conformai Laplacian, together with an explicit computation on the hemisphere H\ 0. Introduction The functional determinant det A of an elliptic differential operator A is important in quantum field theory because it provides a regularization of the functional integral. Originally of interest on four-dimensional manifolds, these objects have recently been intensively studied by physicists and mathematicians in two dimensions, in connection with string theory, the isospectral problem, and uniformization problems. In each of these applications, the operator A = Ag should be built naturally from a Riemannian metric g on a compact manifold M (and possibly some related extra information, like spin structure), and one is concerned with detAg as a functional on the cone {g} of Riemannian metrics on M, or more precisely, the quotient of {g} by the action of the diffeomorphism group Diffeo(M). A key point has been the behavior of the determinant under conformai change of g ; that is, replacement of g by Ù2 g, where Q is Received by the editors October 28, 1992 and, in revised form, September 21, 1993. 1991 Mathematics Subject Classification. Primary 58G25, 58G20. Research of T. Branson partially supported by the N.S. F. and by the Danish Research Council. Research of P. Gilkey partially supported by the N.S. F. and by the Max Planck Institute for Mathematics (Bonn). ©1994 American Mathematical Society 0002-9947/94 $1.00+ $. 25 per page
Spontaneous Longitudinal Combustion Instability in a Continuously-Variable Resonance Combustor

An experimental study of spontaneous longitudinal high-frequency combustion instabilities in a high-pressure model rocket combustor is described. The experiment is designed to efficiently obtain stability data under variable resonance conditions in a single test. A traversing choked axial oxidizer inlet is used to vary the coupled resonances between the variable-length oxidizer tube and the fixed-length combustion chamber, thereby changing the temporal and spatial relationship between the fluid mechanical resonances in the oxidizer tube and the local pressure oscillations at the head end of the combustor. Marked transitions between pressure-fluctuation amplitudes and spectral contents are observed as the injector tube length changes. Stable-to-unstable and unstable-to-stable transitions are observed. Depending on the injector tube length, the first dominant injector-coupled resonance ranged from1200 to 1500Hz.The high-frequency pressure oscillation amplitudes varied from less than 10%ofmean pressure to greater than 30% of chamber pressure. Spectrograms are used to assess the global frequency contributions, and power spectral densities are used as a quantitative measure of the stability characteristics and to identify the most unstable geometry. The combustor was also operated in fixed-tube-length mode to measure linear growth rates and compare limit cycle amplitudes. The experimental results provide a basis for comparison with stability models, and their use in conjunction with reliable computational fluid dynamics models can potentially provide detailed insight into the physics of self-excitation and limit cycle behavior in a practical system.
Molecular hydrogen kinematics in the ring-like planetary nebula NGC 6781

This paper presents the radial velocity mapping of the molecular hydrogen in the ring-like planetary nebula NGC 6781. Observations of the H 2 $v=1{-}0$ S (1) emission line (2.122 μ m, $\Delta \lambda=0.02$ μ m) were obtained by Fabry-Perot spectroscopy. These observations provide a very detailed map of the kinematic structure of the molecular hydrogen envelope in NGC 6781. The kinematic structure is explained with a model consisting of a thin hollow cylinder whose axis is tilted with respect to the line of sight, and gas expanding radially outward with a velocity proportional to the distance to the central star. Molecular hydrogen emission was detected at LSR velocities ranging from -6.2 to +57.1 km s -1 , with peak intensities between +15.7 and +25.5 km s -1 . There is evidence that the molecular hydrogen envelope is excited by shocks from the ionization front. The mass of molecular gas is estimated to be of the order of 0.2 $M_\odot$. The emergent picture from the H 2 kinematic structure supports the scenario where the structure of NGC 6781 was formed from the ionization and destruction of an ellipsoidal molecular envelope that began with the destruction and ionization of the least dense polar caps and will continue until the densest molecular material at nebular waist is fully ionized.
The mobilities of xenon ions in xenon and the derived charge transfer cross section for Xe+(2P3,2) ions in xenon

A drift tube of the four-gauze Tyndall-Powell type has been used to obtain accurate mobility data for ground-state Xe+(2P3/2) ions, metastable Xe+(2P1/2) ions and molecular Xe2+/Xe3+ ions in xenon at room temperature (294.1+or-0.2K) over a wide E/N range (E is the electric field strength and N is the gas number density). The measurements were made at E/N values from 50 to 10000 Td in the case of the Xe+(2P3/2) ions, and from 50 to 250 Td in the case of the Xe2+/Xe3+ ions. The mobility data for the Xe+(2P1/2) ions were derived by a manual deconvolution of the Xe+(2P3/2)+Xe+(2P1/2) peak into two Gaussian curves. Owing to low resolution, the data for the Xe+(2P1/2) ions could only be derived for E/N values less than 900 Td. The mobility of the Xe+(2P3/2) ions was found, over the common E/N range, to be systematically 6% lower than that of the Xe+(2P1/2) ions. The charge transfer cross section sigma c, calculated for Xe+(2P32/) ions in xenon over the energy range 0.38 to 4.46 eV (lab) using the theory of Skullerud (1969), is estimated to be in error by less than +or-5%.
Frequency analysis of nanotubes with consideration of surface effects

Consideration of surface effects in microscaled and nanoscaled materials is important for accurate prediction of their dynamic behavior. In this study, the Timoshenko beam model is modified to include the surface effects and used to analyze the vibration of nanotubes as well as calculate their natural frequencies. The thin surface layers have been taken into account for rotary inertia computation. Through an example it is shown that dynamic behavior of nanoscaled tubes with consideration of surface effects considerably deviates from the results obtained by classical theories. Plots illustrating such deviations are given to support the conclusions.
High-Order Approximations and Generalized Necessary Conditions for Optimality

In this paper we derive generalized necessary conditions for optimality for an optimization problem with equality and inequality constraints in a Banach space. The equality constraints are given in operator form as $Q=\{x\in X:F(x)=0\}$ where $F:X\rightarrow Y$ is an operator between Banach spaces; the inequality constraints are given by smooth functionals or by closed convex sets. Models of this type are common in the optimal control problem. The paper addresses the case when the Frechet-derivative F '(x*)is not onto and hence the classical Lyusternik theorem does not apply to describe the tangent space to Q. In this case the classical Euler--Lagrange type necessary conditions are trivially satisfied, generating abnormal cases. A high-order generalization of the Lyusternik theorem derived earlier [U. Ledzewicz and H. Schattler, Nonlinear Anal. , 34 (1998), pp. 793--815] is used to calculate high-order tangent cones to the equality constraint at points $x_{*}\in Q$ where F '(x*) is not onto. Combining these with high-order approximating cones related to the other constraints of the problem (feasible cones respectively cones of decrease) a high-order generalization of the Dubovitskii--Milyutin theorem is given and then applied to derive generalized necessary conditions for optimality. These conditions reduce to classical conditions for normal cases, but they give new and nontrivial conditions for abnormal cases.
The radio properties of CD galaxies in Abell clusters. II: the VLA sample

The radio properties of a sample of 91 cD galaxies in Abell clusters are presented. The radio data consist of new 6 cm VLA maps with a resolution of 1″-2″ as well as data from the literature. The principal goal of this project was to investigate the possible effects of global and local cluster properties on the radio properties of cDs. The dominant predictor of central radio activity is the presence of x-ray cooling flows, as reported in Paper I [Burns, J. O. , AJ, 99, 14 (1990)].
Electron Temperature Measurement in a Premixed Flat Flame Using the Double Probe Method

The electron temperatures Te were measured using a double probe in a premixed methane flame produced by a calibration burner according to Hartung et al. The experiment was performed at atmospheric pressure. In contrast to other authors, we have managed to find typical nonlinearities corresponding to the retarding electron current region and to calculate electron temperatures using a suitable fit on the basis of the measured characteristics. A Pt‐Rh thermocouple was used to measure temperatures Th corresponding to “heavy” species. Our results indicate that the flame plasma can be considered to be weakly non‐isothermic — Te = (2400–4000) K, Th = (1400–1600) K. On the basis of measurement of the saturated ion current, the number density of the charged particles was estimated at (0.3–3.8) · 1017 m‐3. The trends in Te and Th in dependence on the positions of the probes and thermocouple in the flame differ substantially; this fact has not yet been explained (© 2012 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The Russo-Seymour-Welsh Theorem and the Equality of Critical Densities and the "Dual" Critical Densities for Continuum Percolation on $|mathbb{R}^2$

A Russo-Seymour-Welsh (RSW) theorem is established for continuum percolation on R2. The equality of various definitions of critical densities for the continuum percolation on R2 is deduced as an application of the RSW theorem. It is also shown that various notions of the size of a cluster yield the same notion of critical density.
On the application of the strong property fluctuation theory for homogenizing chiral-in-chiral composites

The bilocal approximation is used along with the strong property fluctuation theory (SPFT) to homogenize (i.e. estimate the effective constitutive properties of) a chiral-in-chiral composite. Important properties of the covariance function of the spatial distribution of the two materials are deduced and interpreted with respect to the homogenization results. Comparison is made with the Maxwell Garnett and the Bruggeman approaches. The correlation length is an additional parameter that distinguishes the SPFT in the bilocal approximation from the Bruggeman approach (as well as from the Maxwell Garnett approach). The SPFT in the bilocal approximation turns out to be a size-dependent extension of the Bruggeman approach, the two homogenization procedures yielding almost the same results at very long wavelengths but not at shorter wavelengths.
Dynamic responses of a two-dimensional flapping foil motion

The investigation of a flapping foil, which is used as a basic mode of the flapping-based locomotion in insects, birds, and fish, is performed by solving the Navier-Stokes equations numerically. In this Brief Communication we provide insight into the understanding of dynamics of a flapping foil. A critical flapping Reynolds number based on the flapping frequency and amplitude, above which a forward flapping movement occurs, is predicted. The dynamics of the flapping foil are analyzed in two dynamic responses, i.e., an oscillatory movement and a steady movement, which depend on the density ratio between the foil and the surrounded fluid. The steady movement response is related to the forward flapping motion. The Strouhal number that governs a vortex shedding for the forward flapping foil is calculated and lies in the range where flying and swimming animals will be likely to tune for high propulsive efficiency.
ON THE RATE OF SPREAD FOR SOME REACTION-DIFFUSION MODELS OF FOREST FIRE PROPAGATION

A model of forest fire propagation, including drying, pyrolysis, heat convection, heat conduction, and radiative transfer, is presented. This model has been obtained by asymptotic expansion and has the generic form of a system of reaction-diffusion equations. One of the aims of the present work is to link this type of reaction diffusion models to models that rely on the concept of rate of spread. The rate of spread is defined as the solution to a nonlinear eigenvalue problem. The solution to this eigenvalue problem is obtained as a perturbation expansion in the thermal conductivity of the solid phase. The calculated rates of spread for two flame models compare favorably to experimental values.
Accurate Position of SGR 1900+14 by Bursts and Changes in Pulse Period and Folded Pulse Profile with ASCA

The Advanced Satellite for Cosmology and Astrophysics (ASCA) observed the soft gamma repeater SGR 1900+14 on 1998 April 30-May 1 and discovered a pulsar with a period of 5.1589715(8) s from the known X-ray source of RX J190714.2+0919.3. Four months later, on September 16-17, ASCA observed SGR 1900+14 again just after the giant burst on 1998 August 27. Comparing the observations in September with those in April, there are several changes in characteristics. The pulse period changed to 5.160295(3) s, and thus the long-term period derivative is 1.1 × 10-10 s s-1. This strongly supports a magnetar model. The folded pulse profile in 2-10 keV largely changed from three peaks in April to one simple peak, while the steady intensity increased by a factor of 2. Finally, we successfully determined the accurate location of SGR 1900+14 by the bursts with an accuracy of 1. ′5 in diameter.
Uniform Approximation by Neural Networks

LetD? Rdbe a compact set and let? be a uniformly bounded set ofD? Rfunctions. For a given real-valued functionfdefined onDand a given natural numbern, we are looking for a good uniform approximation tofof the form ? ni=1a1? i, with? i? ,ai? R. Two main cases are considered: (1) whenDis a finite set and (2) when the set? is formed by the functions? v,b(x)? s(v·x+b), wherev? Rd,b? R, andsis a fixedR? Rfunction.
River training and sediment management with submerged vanes

This book summarizes the present theoretical and practical knowledge on the submerged vane technique. Submerged vanes represent a novel, eco-friendly and often cost-effective technique for river training and sediment management. The book represents a guideline for river engineers to determine when submerged vanes may be used instead of traditional river training strategies and how they should be designed and placed. It focuses on the design objectives related to four applications: (1) river bank protection; (2) river bed stabilization and/or sediment redistribution within a cross-section; (3) sediment control at water intakes or diversions and (4) stabilization of river channel alignment. A number of papers were published on submerged vanes describing the technique and its application. The book represents a successful attempt to compile the corresponding theoretical background and latest design guidelines within a single source. Chapter 1 provides a general overview of submerged vanes and a brief description of relevant applications. In Chapter 2, the theoretical background for the design of arrays of submerged vanes is briefly presented and the governing equations for design calculations are derived. As the governing equations cannot be easily solved analytically, three design graphs are presented facilitating the design of submerged vane systems. The graphs are based on selected boundary conditions and their accurate application may require interpolation based on various parameters. Chapter 3 contains the description of laboratory experiments which were carried out with both rigid and mobile channel beds. The data acquired in these experiments are used to validate the underlying theory and the design guidelines formulated in Chapter 2. Chapter 4 presents a brief overview of the required steps for the design procedure taking into account different applications. This overview is followed by five examples illustrating the design procedure and the application of the design graphs. The examples are helpful for the understanding of the design procedure and may serve as model examples for similar projects. Chapter 5 reviews and describes 12 existing field installations of submerged vanes located in the USA, Taiwan, Nepal and New Zealand. The installations were selected to cover various applications and a wide range of flow and sediment conditions. The success of these installations clearly shows the applicability of submerged vanes for river training and sediment management. Chapter 6 summarizes the design guidelines and provides further valuable information on typical dimensions for vane design and layout, primary design considerations, vane materials and limitations to vane usage. The book is well written and the large number of figures and illustrations help readers to understand the key elements of this Journal of Hydraulic Research Vol. 48, No. 4 (2010), pp. 553–554 doi:10.1080/00221686.2010. 491700
Leader-following consensus of second-order non-linear multi-agent systems with directed intermittent communication

This study addresses leader-following consensus problems for multi-agent systems with second-order non-linear dynamics, under the assumption that each agent can only communicate with its neighbouring agents intermittently and the communication topology does not keep strongly connected or contain a spanning tree all along. Firstly, a class of distributed consensus algorithms are designed only based on the relative local intermittent information. Notions of completely and partly intermittent communication are proposed. Some sufficient conditions are derived for achieving consensus tracking under a general fixed topology with completely and partly intermittent communication. Then, as an extension, leader-following consensus tracking is studied under time-varying intermittent communication topologies. Finally, the effectiveness of the main results is illustrated by numerical simulations.