Miracle-dz/UniFAR-FTUs huggingface dataset:
Interference effect of two equal‐sized square cylinders in tandem arrangement: With planar shear flow

Numerical simulations have been performed for flow past two equal‐sized square cylinders in tandem arrangement subjected to incoming planar shear flow. Effect of L/d ratio and the shear parameter has been studied. The range of L/d ratio (ratio of center‐to‐center distance (L) to cylinder width (d)) is varied from 2 to 7 and the non‐dimensional shear parameter (K) is varied from 0.0 to 0.4 in steps of 0.1. For all the cases the Reynolds number (Re) based on centerline velocity and cylinder width is fixed at 100. The results are compared with that of isolated square cylinder with uniform flow. Strouhal number decreases with increasing shear parameter. There are more than one shedding frequency at high shear parameters and L/d ratios. The mean drag coefficient is decreased with shear parameter and lesser than that of the single cylinder. The root mean square (RMS) value of both lift and drag coefficients is higher for the downstream cylinder for all values of shear parameter. With increasing L/d ratio, for both lift and drag, the RMS value increases and then decreases for upstream cylinder, whereas it continuously increases for the downstream cylinder. The stagnation point is moved towards the top leading edge with increasing shear. The critical L/d ratio, which is defined as the distance between two cylinders, beyond which the vortex shedding from the upstream cylinder occurs, decreases with increasing shear parameter. Copyright © 2007 John Wiley & Sons, Ltd.
Phase locking of two long-pulse, high-power magnetrons

We have phase locked a pair of long-pulse, high-power, secondary-emission magnetrons to an RF-isolated low-power driver via a waveguide directional coupler. With the 3 dB hybrid coupler, the peak and average power sent back towards the driver were lower than the total power by factors of 20 and 100, respectively. A dual-channel, thyratron-switched line-type modulator was used to power the magnetrons in parallel. In this experiment the total microwave power from the pair of phase-locked high-power magnetrons was limited to 48 MW for 700 ns pulses and 46 MW for 900 ns pulses because one of the high-power magnetrons would only operate at or below half power. Experimental results from this repetitively-pulsed (10 Hz) phase-locked magnetron pair are presented which show excellent phase stability of several degrees both during the pulse and from pulse-to-pulse. >
Determination of the specific resistance of individual freestanding ZnO nanowires with the low energy electron point source microscope

A low energy electron point source microscope is used to determine the electrical conductivity of freestanding ZnO nanowires. The nanowires were contacted with a manipulation tip and I-V curves were taken at different wire lengths. From those, the specific resistance was calculated and separated from the contact resistance. By comparing the specific resistances of ZnO nanowires with diameters between 1100 and 48nm, a large surface contribution for the thin nanowires was found. A geometric model for separation between surface and bulk contributions is given.
Photoevaporation of Protostellar Disks. V. Circumstellar Disks under the Influence of Both Extreme-Ultraviolet and Far-Ultraviolet Radiation

The evolution and appearance of protostellar disks can be significantly altered by their UV environment. We investigate numerically the photoevaporation of protostellar disks under the influence of an external radiation field with both EUV (hν > 13.6 eV) and FUV (6 eV < hν < 13.6 eV) components. Our two-dimensional axisymmetric radiation hydrodynamics calculations begin with star-disk configurations resulting from previously published collapse simulations. We follow the evolution after the external UV radiation source has been turned on. We consider the transfer of both direct (from the UV point source) as well as diffuse radiation fields simultaneously with the ionization of hydrogen and carbon. A simplified cooling function is employed which assumes that the carbon ionization front separates the molecular region from the region in atomic or ionized form. For some simulations an isotropic stellar wind has been included at the position of the disk's central star. At selected evolutionary times a frequency-dependent ray-tracing diagnostic code is used to calculate emission line spectra and emission line maps over the volume of interest. The interaction of the FUV-induced neutral flow at the disk surface with the direct and diffuse EUV radiation fields leads to the typical head-tail objects with bright emission line crescents and tails pointing away from the external radiation source. The properties of the head-tail objects are in agreement with the properties of the proplyds in the Orion Nebula, M8, NGC 2024, and—in a more extreme UV environment—of the newly discovered proplyds in NGC 3603. After losing material via photoevaporation over a time ≳105 yr, our initially rather massive disks are reduced to typical observed disk masses. At this time the radius of the disk, the radius of the hydrogen ionization front, and the length of the tail are compatible to observed proplyds. Our model disks can be either silhouetted or nonsilhouetted in the emission line maps, depending on orientation. The [O III] 5007 Å emission appears more diffuse than [O II] 3726 Å, because the abundance of O III is low near the hydrogen ionization front and in the shadow regions along the tail. Monopolar and bipolar microjets emerging from the proplyds can be explained by spherically symmetric stellar winds hydrodynamically focused by the neutral evaporating flow from the disk surface.
A MULTIGRID APPROACH TO THE OPTIMIZATION OF SYSTEMS GOVERNED BY DIFFERENTIAL EQUATIONS

We consider the optimization of systems governed by differential equations. In such problems, one has a set of design variables along with a set of state variables, the two sets of variables being related through a set of differential equation constraints. The overall computational cost of optimization is determined by the level of discretizatio n used to numerically solve the governing differential equations. If a fine discretization is used, one expects a greater degree of physical and mathematical fidelity to the problem under consideration, but the large number of state variables can make the cost of optimization prohibitive. We present here a multigrid algorithm that uses solutions to optimization problems based on coarser discretizations, which are less expensive to compute, in a systematic manner to help us obtain the solution of the optimization problem based on a finer discretization. Of interest is the fact that the approach is applicable in situations where multigrid applied only to the solution of the differential equation might not be applicable or effective. We give evidence (both theoretical and numerical) that a multigrid approach can often be successful in the more general setting of optimization.
Investigation of the stress‐strain state of the laminated shallow shells by R‐functions method combined with spline‐approximation

The bending behavior of the laminated shallow shells under static loading has been studied using the R‐functions theory together with the spline‐approximation. Formulation is based on the first order shear deformation theory. Due to usage of the R‐functions theory the laminated shallow shells with complex shape and different types of the boundary conditions can be investigated. Application of the spline‐approximation allows getting reliable and validated results for non concave domains and domains with holes. The proposed method is implemented in the appropriate software in framework of the mathematical package MAPLE. The analysis of influence of certain factors (curvature, packing of layers, geometrical parameters, boundary conditions) on a stress‐strain state is carried out for shallow shells with cut‐outs. The comparison of obtained results with those already known from literature and results obtained by using ANSYS are also presented.
Performance research of Gaussian function weighted fuzzy C-means algorithm

Fuzzy C-Means (FCM) algorithm is a fuzzy pattern recognition method. Clustering precision of the algorithm is affected by its equal partition trend for data set of large discrepancy of each class samples number, and the optimal clustering result of the algorithm mightn't be a right partition in this case. In order to overcome this disadvantage, a Gaussian function Weighted Fuzzy C-Means (WFCM) algorithm is proposed, which the weighted function is produced by a Gaussian function calculating dot density of each sample. To certain extent, the WFCM algorithm has not only overcome the limitation of equal partition trend in fuzzy Cmeans algorithm, but also been favorable convergence and stability. The calculation of the weighted function and the choice of sample dot density range restriction value for the algorithm are both objective. When partially supervised information obtained from a few labeled samples is introduced to the WFCM algorithm, the classification performance of the WFCM algorithm is further enhanced and the convergent speed of objective function is further accelerated.
The oscillations of a fluid droplet immersed in another fluid

From an analysis of small oscillations of a viscous fluid droplet immersed in another viscous fluid a general dispersion equation is derived by which frequency and rate of damping of oscillations can be calculated for arbitrary values of droplet size, physical properties of the fluids, and interfacial viscosity and elasticity coefficients. The equation is studied for two distinct extremes of interfacial characteristics: (i) a free interface between the two fluids in which only a constant, uniform interfacial tension acts; (ii) an ‘inextensible’ interface between the two fluids, that is, a highly condensed film or membrane which, to first order, cannot be locally expanded or contracted. Results obtained are compared with those previously published for various special cases. When the viscosities of both fluids are low, the primary contribution to the rate of damping of oscillations is generally the viscous dissipation in a boundary layer near the interface, in both the free and inextensible interface situations. For this reason inviscid velocity profiles, which do not account for the boundarylayer flow, do not lead to good approximations to the damping rate. The two exceptions in which the approximation based on inviscid profiles is adequate occur when the interface is free and either the interior or exterior fluid is a gas of negligible density and viscosity.
Relativity and the periodic system of elements

Relativistic effects are defined as the difference between the case of a finite speed of light as in the world we live in and of an infinite speed of light as assumed by most theoretical chemistry. Ways in which these relativistic effects can be used to explain some of the most conspicuous anomalies in the latter half of the periodic table comprise this article. These relativistic effects are found to be particularly strong around gold in the table. (BLM)
Surface-enhanced Raman scattering hot spot isolation using surface-enhanced multiphoton lithography

In this Manuscript, we present the fabrication and spectroscopic characterization of a large-area surfaceenhanced Raman scattering (SERS) substrate, as well as a method for improving femtomole-level trace detection (109 molecules) using this substrate. Using multiphoton-induced exposure of a commercial photoresist, we physically limit the available molecular adsorption sites to only the electromagnetic "hot spots" on the substrate. This process prevents molecules from adsorbing to sites of weak SERS enhancement, while permitting adsorption to sites of extraordinary SERS enhancement. For a randomly adsorbed submonolayer of benzenethiol molecules the average Raman scattering cross-section of the processed sample is 27 times larger than that of an unprocessed SERS substrate.
An efficient computational method for statistical moments of Burger's equation with random initial conditions

The paper is concerned with efficient computation of numerical solutions to Burger's equation with random initial conditions. When the Lax-Wendroff scheme (LW) is expanded using the Wiener chaos expansion (WCE), random and deterministic effects can be separated and we obtain a system of deterministic equations with respect to Hermite-Fourier coefficients. One important property of the system is that all the statistical moments of the solution to the Burger's equation can be computed using the solution of the system only. Thus LW with WCE presents an alternative to computing moments by the Monte Carlo method (MC). It has been numerically demonstrated that LW with WCE approach is equally accurate but substantially faster than MC at least for certain classes of initial conditions.
Brownian motion of actin filaments in confining microchannels

Since the cytoskeletal protein actin is one of the principal building blocks of mammalian cells, it has recently been arousing much interest. Here, we address questions concerning the mechanical and dynamic behaviour of individual actin filaments in confining geometries which mimic the dense cytoskeletal network in eukaryotic cells. Microfluidic devices fabricated by soft photolithography in combination with fluorescence microscopy are used to manipulate, observe and characterize these biopolymers. The polymer statistics is strongly dependent on the characteristics of the surroundings such as the degree of confinement and hydrodynamical flow. Besides this, the intrinsic mechanical properties of the filaments are dominated by the persistence length and the contour length. We analyse the tangent–tangent correlation and the radial distribution function in terms of a confining potential and the contour length of the filaments. In addition, we show that hydrodynamic flow can be successfully used to apply controlled local stress on actin filaments. Our results can be surprisingly well described by a straightforward model which approximates the confining energy of the microchannels using a parabolic potential.
A Projection Operator for Representing Sharp Features using Visibility

AbstractWe propose a projection operator for point sets without normal vector information. Based on the visibility of points, it is possible to represent sharp features when points are projected on the surface without normal vector information. Our method is based on the Moving Least- Square Surface projection operator. Visibility computation is utilized to avoid average computation of points near sharp features when selecting points, in which visibility information is computed before starting the projection for selecting point clouds of one side. We also demonstrate the effectiveness of our visibility approach through several experiments.
Hydromagnetic Double-Diffusive Laminar Natural Convection in a Radiatively Participating Fluid

ABSTRACT Two-dimensional hydromagnetic double-diffusive convection of a radiatively participating fluid confined in a rectangular enclosure is studied numerically for fixed Prandtl, Rayleigh, and Lewis numbers, Pr = 13.6, Ra = 105, Le = 2. Uniform temperatures and concentrations are imposed along the vertical walls, while the horizontal walls are assumed to be adiabatic and impermeable. The damping and stabilization effects of an external horizontal magnetic field are studied for three different optical thicknesses of the semitransparent fluid as well as for an opaque medium. For moderate optical thickness, a steady compositionally dominated flow is observed for all values of Hartmann number considered, and the magnetic damping is remarkably lower than in the opaque medium, for which the flow is always thermally dominated. For optically thin and optically thick media, the thermally dominated flow is stabilized and becomes compositionally dominated as soon as the Hartmann number is increased.
Subjective trajectory characterization: acquisition, matching, and retrieval

We describe a system that automatically tracks moving objects in a scene and subjectively characterizes the object trajectories for storage and retrieval. A multi-target color-histogram particle filter combined with besthypothesis data association is the foundation of our trajectory acquisition algorithm. To improve computational performance, we use quasi-Monte-Carlo methods to reduce the number of particles required by each filter. The tracking system operates in real-time to produce a stream of XML documents that contain the object trajectories. To characterize trajectories subjectively, we form a set of shape templates that describes basic maneuvers (e.g., gentle turn right, hard turn left, straight line). Procrustes shape analysis provides a scaleand rotation-invariant mechanism to identify occurrences of these maneuvers within a trajectory. To add spatial information to our trajectory representation, we partition the two-dimensional space under surveillance into a set of mutually exclusive regions. A temporal sequence of region-to-region transitions gives a spatial representation of the trajectory. The shape and position descriptions combine to form a compact, high-level representation of a trajectory. We provide similarity measures for the shape, position, and combined shape and position representations.
Inner ellipsoidal approximation of membership set: a fast recursive algorithm

In robust system identification the measurement errors are usually assumed to be unknown but bounded, leading to a description of the model parameters in terms of a membership set. Due to the difficulty in obtaining an exact description of this set, in the past several methods have been proposed for its approximation. In the paper a fast recursive algorithm for the determination of an inner ellipsoidal approximation of the membership set is presented.
A Survey regarding the Reporting of Simulation Studies

Abstract Hoaglin and Andrews (1975) proposed standards for computational practice and the reporting of computation-based studies. They observed that “statisticians … often pay too little attention to their own principles of design. ” To see if the design and reporting had improved, we surveyed five major statistical journals for 1975, 1978, and 1981 to ascertain whether reported simulation studies involved a specified design, justified the choice of the number of iterations, and specified the random number generator(s) used. Eighteen percent of the 1,198 papers surveyed included results based on simulation. We found that 9% of the papers including a simulation study justified the choice of the number of iterations and 44% at least partially specified the random number generator. Hoaglin and Andrews's observation appears still to be true.
The Fourth Data Release of the Sloan Digital Sky Survey

This paper describes the Fourth Data Release of the Sloan Digital Sky Survey (SDSS), including all survey-quality data taken through 2004 June. The data release includes five-band photometric data for 180 million objects selected over 6670 deg2 and 673,280 spectra of galaxies, quasars, and stars selected from 4783 deg2 of those imaging data using the standard SDSS target selection algorithms. These numbers represent a roughly 27% increment over those of the Third Data Release; all the data from previous data releases are included in the present release. The Fourth Data Release also includes an additional 131,840 spectra of objects selected using a variety of alternative algorithms, to address scientific issues ranging from the kinematics of stars in the Milky Way thick disk to populations of faint galaxies and quasars.
Facilitating Strategies for Solving Work‐Energy Problems in Graphical and Equational Representations

Our previous research has suggested that the major difficulty students have when solving physics problems posed in graphical and equational representations is due to students’ inability to appropriately activate the required mathematical knowledge in the context of a physics problem. Based on these results, we developed problem sets for each major topic in introductory mechanics. Each set consisted of one or two pairs of matched math and physics problems, debate problems, and problem posing tasks. We conducted focus group learning interviews with two groups of students working in pairs: a treatment group working on our research‐based problem sets and a control group solving isomorphic textbook problems on the same topics. We present here a description of one of our problem sets on Work‐Energy problems as well as a comparison of the performance of the two groups on transfer problems on Work‐Energy involving graphical and equational representations.
On Jones' planar algebras

We show that a certain natural class of tangles 'generate the collection of all tangles with respect to composition'. This result is motivated by, and describes the reasoning behind, the 'uniqueness assertion' in Jones' theorem on the equivalence between extremal subfactors of finite index and what we call 'subfactor planar algebras' here. This result is also used to identify the manner in which the planar algebras corresponding to M⊂M1 and Nop⊂Mop are obtained from that of N⊂M. Our results also show that 'duality' in the category of extremal subfactors of finite index extends naturally to the category of 'general' planar algebras (not necessarily finite-dimensional or spherical or connected or C*, in the terminology of Jones).
Estimation of fuzzy sets for computational colour categorization

Colour is an important visual cue for computer vision applications. However, up to the present, the automatic assignment of names to image regions has not been widely used due to the non- existence of a general computational model for colour categorization. In this paper we present a model for colour naming based on fuzzy set theory, in which each of the 11 basic colour terms defined by Berlin and Kay 1 is modelled as a fuzzy set with a characteristic function which assigns a membership value to the category to any colour sample. The model is based on combining two well known functions, a sigmoid and a gaussian, to define a membership function for colour categories. It is denoted here as the sigmoid-gaussian function and it fulfils a set of properties which makes it adequate to this purpose. The characteristic functions for each colour category have been fitted to data obtained from a psycho-physical experiment and the model has been tested on the Munsell colour array to show its validity. The results obtained indicate that our approach can be very useful as a first step to expand the use of colour naming information in computer vision applications.
Realization of compact broadband rat-race coupler

In this article, a method to miniaturize the broadband rat-race couplers using microstrip nonuniform transmission lines (MNTLs) is presented. The proposed coupler features a compact size on a single circuit layer structure without reactive components and via-holes. The design formulas are developed using ABCD matrix and even–odd mode analysis. The theoretical analysis has been verified by measurement of the manufactured broadband MNTL rat-race coupler with center frequency of 1.35 GHz and 89% fractional bandwidth. The isolation, magnitude, imbalance and phase imbalance are less than –20 dB, 0.5 dB, and 4 degrees, respectively, within 0.75–1.95 GHz frequency bandwidth.