Miracle-dz/UniFAR-FTUs huggingface dataset:
Heat Transfer Enhancement in a Pipe Using a Flow Inverter

Flow inversion, transferring a liquid from the wall region toward the center of the pipe or from the axis toward the heat transfer surface, improves heat transfer in the laminar flow regime. While a fully developed velocity profile is quickly established, a thin thermal boundary layer is preserved for a considerable distance in the pipe behind the flow inverter for highly viscous liquids. Thus the pressure drop is increased only locally (by the inverter itself), while heat transfer enhancement is also seen in a long straight section of the pipe. Two original flow inverter designs were tested in a long pipe (3 m in length) heated by condensing steam, using starch molasses as a working medium. Experiments carried out in the range of Reynolds number 4–60 and Graetz number 150–700 resulted in an increase of 20–35% in the heat transfer coefficient, accompanied by a 30–40% increase in the pressure drop. The experimental results confirm the numerical model prediction (within an extended Reynolds number range starting from 0.1). Thus an almost 40% increase in heat transfer can be expected at the optimal Graetz number in the range 50–100, using only one flow inverter located in the middle of a sufficiently long pipe.
Design and simulation of electrically pumped mode-locked VECSELs

Vertical External Cavity Surface Emitting Lasers (VECSELs) feature scaling to large active areas and combine surface emission with high optical power output. In principle, they can be designed with electrical pumping operating in continuous wave or passively mode-locked operation. In this paper, our design and modeling activities towards a high power passively mode-locked VECSEL are described. In particular, design towards single mode high-power CW operation is discussed as prerequisite for passive mode-locking.
Wavelength-multiplexed analog fiber optic link for wideband radio-frequency and local oscillator signal transmission

A wavelength-multiplexed fiber optic link architecture has been designed for transmitting ri signals with wide instantaneous band width and LO signals at microwave frequencies over long distances. The architecture involves downconverting the input rf signal, directly amplitude modulating a laser diode, transmitting the resulting rf-modulated optical carrier through single-mode fiber, and subsequently up-converting the recovered rf signal to the original band. Wavelength division multiplexing and demultiplexing is used to transmit the local oscillator signal (required for down- and up-conversions) from the transmitter to the receiver through the same fiber. By using a frequency-divided LO signal in conjunction with frequency multipliers, the wideband rf signal can be down/up-conveiled anywhere in the rf spectrum up to 100 GHz. A demonstration link has been implemented using this architecture and operates from 6.3 to 16 GHz. This link uses a 1.3-μm, 10-GHz rf bandwidth laser diode for IF transmission and a 1.55-μm, 1.5-GHz rf bandwidth laser diode for LO transmission.
Spectroscopy of galaxies in distant clusters. IV - A catalog of photometry and spectroscopy for galaxies in seven clusters with z in the range of 0.35 to 0.55

Photometry and spectroscopy for seven deep fields containing distant clusters of galaxies with z in the range of 0.35 to 0.55 are presented. Positions and photometric parameters, including r-magnitudes g - r and r - i colors, surface brightnesses, and photometric profile types are given for about 2000 galaxies. Low-resolution spectroscopy is obtained from which redshifts are determined for 289 objects, of which 190 are cluster members. These are classified according to dominant spectral features, and examples are plotted in each cluster. Color-magnitude and color-color diagrams are formed which show trends in the cluster populations, and maps are made of the cluster field using the color-color relations to increase the contrast of cluster over field. Galaxies with spectra typical of old stellar populations cluster most strongly, with active galaxies, those with recent or ongoing star formation, or an active nucleus, distributed more diffusely. The g - r color is well correlated with active star formation as judged from spectral features.
The use of stereology to determine the partial two-body correlation functions for hard sphere ensembles

The authors present here a method of finding the bulk two-body correlation functions for an isotropic ensemble of hard spheres by examining a single section through the ensemble. The authors derive an integral equation which gives the probability of seeing a disc of radius sigma 1 a distance rho from a disc of radius sigma 2, in the cross-section. The authors solve this explicitly for the case where the distribution of sphere radii in the bulk is a discrete distribution and hence obtain a discrete set of partial two-body correlation functions for the bulk ensemble.
Implantation of radioisotopes at ISOLDE a novel source production technique for diffusion studies in solids

The on-line implantation of radioisotopes produced at the ISOLDE facility is described as a novel source production technique for diffusion studies in solids. The radioactive implants can be used to investigate basic lattice and grain boundary diffusion properties in solids. Potentials and limitations of this technique will be discussed and illustrated by examples which concern lattice diffusion of 121Te, 195Au, and 75Se in single crystals of various materials and of 121Te in Ag polycrystals. The examples show that the combination of production and on-line implantation of radioisotopes opens new possibilities for diffusion studies in solids. Die on-line-Implantation von Radioisotopen, die mit Hilfe des Grosgerates ISOLDE erzeugt wurden, wird als neue Quelltechnik fur Diffusionsuntersuchungen in Festkorpern beschrieben. Die radioaktiven Implantate konnen verwendet werden, um grundlegende Untersuchungen zur Volumen- und Korngrenzendiffusion in Festkorpern durchzufuhren. Moglichkeiten und Grenzen dieser Technik werden diskutiert und mit Hilfe von Beispielen illustriert, welche die Volumendiffusion von 121Te, 195Au und 75Se in Einkristallen verschiedener Materialien und die Diffusion von 121Te in Ag-Polykristallen betreffen. Die Beispiele zeigen, das die Kombination von Erzeugung und on-line-Implantation von Radioisotopen neue Moglichkeiten fur Diffusionsuntersuchungen in Festkorpern eroffnet.
Differential geodesic mathematical morphology

Following a PDE-based formulation of low-level vision, recent works have attempted to cast classical mathematical morphology into the axiomatrix framework of scale-space theory. This effort has led to derive continuous elementary morphological operators and revealed deep connections with the theory of reactive PDEs. Until now, researchers have focused their attention of Euclidean morphology. This article aims at setting up the foundations of differential geodesic mathematical morphology. Specifically, we define multiscale geodesic erosions and dilations, and derive their generating PDEs for arbitrary n-dimensional structuring sets or functions. Geodesic reconstruction then corresponds to steady-states of these equations for particular initial conditions. Geodesic morphological operators are further embedded into a general class of one-parameter operator semigroups, called geodesic scale-space operators. Within this framework, regularized geodesic operators are defined in a natural fashion by augmenting the basic PDEs with a diffusive, scale-space-admissible component. Finally, efficient numerical implementations based on monotonic conservative schemes are presented in details. These developments provide the theoretical basis for PDE-based formulations of watershed segmentation and geodesic skeleton computation.
Controllability and Stabilizability Theory for Linear Partial Differential Equations: Recent Progress and Open Questions

This paper is an assessment of the current state of controllability and observability theories for linear partial differential equations, summarizing existing results and indicating open problems in the area. The emphasis is placed on hyperbolic and parabolic systems. Related subjects such as spectral determination, control of nonlinear equations, linear quadratic cost criteria and time optimal control are also discussed.
Application of the physics of plasma sheaths to the modeling of rf plasma reactors

An equivalent circuit model is presented for a planar rf plasma reactor. The physical properties of the plasma sheath adjacent to the electrodes are incorporated in the model. The sheath capacitances and the conduction currents through the sheaths are time varying and have a highly nonlinear dependence on the potentials across the plasma sheaths. The model shows that the waveforms of the voltage differences across the sheaths are highly nonsinusoidal and agree with reported measurements.
Vibration analysis of a partially treated laminated composite magnetorheological fluid sandwich plate

In this study, the vibration responses of a partially treated laminated composite magnetorheological (MR) fluid sandwich plate have been investigated. The governing differential equations of motion for a partially treated laminated sandwich plate embedding MR fluid and rubber as the core layer and the laminated composite plate as the face layers are presented in finite element formulation. The validity of the developed finite element formulation is demonstrated by comparing the results in terms of natural frequencies derived from the present finite element formulation with the experimental measurements. Various configurations of a partially treated laminated composite MR fluid sandwich plate are considered to study the effect of location and size of the MR fluid segment under various boundary conditions. The effect of magnetic field on the variation of natural frequencies and loss factor of the partially treated laminated composite MR fluid sandwich plate are also analyzed for various configurations at different boundary conditions. The free vibration mode shapes of various configurations of a partially treated laminated composite MR fluid sandwich plate are also presented. The forced vibration responses of the various configuration of a partially treated laminated composite MR fluid sandwich plate are also analyzed under harmonic force excitations. This analysis suggests that the natural frequency, loss factor and transverse displacements of the partially treated laminated composite MR fluid sandwich plate are strongly influenced by the location and size of the MR fluid segment apart from the intensities of the applied magnetic field. The application of the partial treatment alters the deflection pattern of the sandwich plate, particularly the location of peak deflection, which shows that it can be applied to critical components of a large structure to realize a more efficient and compact vibration control mechanism with variable damping.
FIRST‐ORDER INTEGER‐VALUED AUTOREGRESSIVE (INAR(1)) PROCESS

Abstract. A simple model for a stationary sequence of integer-valued random variables with lag-one dependence is given and is referred to as the integer-valued autoregressive of order one (INAR(1)) process. The model is suitable for counting processes in which an element of the process at time t can be either the survival of an element of the process at time t - 1 or the outcome of an innovation process. The correlation structure and the distributional properties of the INAR(1) model are similar to those of the continuous-valued AR(1) process. Several methods for estimating the parameters of the model are discussed, and the results of a simulation study for these estimation methods are presented.
The Measurements of Pollution in the Troposphere (MOPITT) Instrument: Overall Performance and Calibration Requirements

Abstract The Measurements of Pollution in the Troposphere (MOPITT) instrument will monitor the global concentrations of carbon monoxide and methane. It will be flown on the Earth Observing System Satellite AM-I. This paper briefly describes the scientific objectives, performance requirements, and specifications. It primarily focuses on the pre- and postlaunch calibration requirements. The hardware requirements and methodology for calibration are also discussed as well as cross-calibration and validation of MOPITT with an underflying aircraft MOPITT.
A combined finite element-boundary element formulation for solution of two-dimensional problems via CGFFT

ABSTRACT A method for the computation of electromagnetic scattering from arbitrary two-dimensional bodies is presented. The method involves a combination of the finite element and boundary element methods with particular emphasis on forms of the boundary integral aimed at reducing the storage requirement. Two types of boundary enclosures are investigated, both leading to convolutional boundary integrals which may be evaluated via the FFT in conjunction with the CG algorithm to reduce the storage requirement. Specifically, the circular and ogival enclosures are considered. Of these, the first leads to completely convolutional integrals, whereas the ogival contour yields partially convolutional integrals and the remaining must be efficiently evaluated to maintain the O(N) memory requirement. Results for several circular and ogival structures are presented and shown to be in excellent agreement with those obtained by traditional methods.
Experimental and Computational Methods for Flow Investigation in High-Speed Multistage Compressor

This study takes place in the frame of a research project to better understand the flow that develops in multistage high-speed compressors. First, the paper presents the high-speed 3.5-stage compressor CREATE and the methods that are considered to increase the data reliability and the investigation capability with such realistic compressors. Second, flow simulations, achieved with three-dimensional unsteady Reynolds-averaged Navier-Stokes computations over the whole compressor spatial and temporal periodicities, are analyzed through a study of their sensitivity to some parameters such as the inlet conditions, the space and time discretization, and technological effects such as tip and hub clearances. Finally the paper focuses on the methodology used to compare the experimental and numerical results over the whole compressor periodicities. The local spatial and temporal flow structures are well estimated. The key is the advection of these structures, which interact with each other and produce a significant part of the flow fluctuations in the downstream stages. The paper presents the zone close to the casing, where losses and blockage are induced by the interaction between the tip leakage flow and the incoming wakes. This is where the numerical simulation has to be improved, in order to accurately predict the performance.
Measurement of the absolute spectral response of an inverse photoemission detector

The absolute quantum yield of an inverse photoemission detector is reported. The detector consists of a 650‐A KBr photoemission film on the mouth of a channeltron with either a CaF2 or a SrF2 window for a low‐pass cutoff filter. The spectral response for the CaF2 window peaks at 9.8 eV with a FWHM of 1.6 eV and a maximum yield of 0.18 pulse/photon, while for the SrF2 window the peak is at 9.3 eV with a FWHM of 1.4 eV and a maximal yield of 0.06 pulse/photon. Performance of the detector was tested by measuring the inverse photoemission spectra from a W(001)‐(1×1) surface.
THE HIGH-ENERGY, ARCMINUTE-SCALE GALACTIC CENTER GAMMA-RAY SOURCE

Employing data collected during the first 25 months of observations by the Fermi-LAT, we describe and subsequently seek to model the very high energy (>300 MeV) emission from the central few parsecs of our Galaxy. We analyze the morphological, spectral, and temporal characteristics of the central source, 1FGL J1745.6−2900. The data show a clear, statistically significant signal at energies above 10 GeV, where the Fermi-LAT has angular resolution comparable to that of HESS at TeV energies. This makes a meaningful joint analysis of the data possible. Our analysis of the Fermi data (alone) does not uncover any statistically significant variability of 1FGL J1745.6−2900 at GeV energies on the month timescale. Using the combination of Fermi data on 1FGL J1745.6−2900 and HESS data on the coincident, TeV source HESS J1745−290, we show that the spectrum of the central gamma-ray source is inflected with a relatively steep spectral region matching between the flatter spectrum found at both low and high energies. We model the gamma-ray production in the inner 10 pc of the Galaxy and examine cosmic ray (CR) proton propagation scenarios that reproduce the observed spectrum of the central source. We show that a model that instantiates a transition from diffusive propagation of the CR protons at low energy to almost rectilinear propagation at high energies can explain well the spectral phenomenology. We find considerable degeneracy between different parameter choices which will only be broken with the addition of morphological information that gamma-ray telescopes cannot deliver given current angular resolution limits. We argue that a future analysis performed in combination with higher-resolution radio continuum data holds out the promise of breaking this degeneracy.
New, compact instrument for pulse‐echo‐overlap measurements of ultrasonic wave transit times

A new instrument is described which permits the travel time of ultrasonic waves to be measured accurately and conveniently by the pulse‐echo‐overlap method (PEO). The accuracy and versatility of the PEO method are reviewed, and optimal methods of preparing and interrogating samples are presented. Extensive data on a large blank of fused silica are presented. Longitudinal and shear wave velocities were calculated from the wave travel times through measured thicknesses, and the elastic moduli were subsequently calculated from the velocities and the measured density. Error analysis shows that the measurement of travel time contributed less than 20 ppm to the total error of about 400 ppm in the calculated moduli.
Heat conduction boundary layers of condensed clumps in cooling flows

La structure des couches limites de conduction thermique des condensations gazeuses plongees dans le gaz intergalactique chaud des amas de galaxies est etudiee au moyen de modeles hydrodynamiques 1D. Des modeles sont calcules pour un facteur d'echelle arbitraire, expliquant la reduction de l'efficacite de la conduction thermique comparee au cas classique de Spitzer. L'accroissement du refroidissement dans le milieu ambiant du aux pertes de conduction thermique est calcule pour une etendue des parametres des condensations
Particle Simulations of Helium Microthruster Flows

Computational results are presented for the flow through a helium microthruster. This device is to be used for fine adjustments in attitude control for a proposed space experiment. The mass-flow rates used by the thruster are very low giving Knudsen numbers at the nozzle throat between 0.01 and 1 based on the stagnation conditions and the nozzle throat diameter. These conditions indicate that low-density effects will dominate the fluid mechanics. Therefore, the flows are computed with a particle simulation scheme [the direct simulation Monte Carlo method (DSMC)]. This study presents an application of the DSMC technique to the complete expansion process of a real thruster: from the stagnation chamber of the thruster, to the far-field expansion of the plume. The numerical approach is evaluated by comparison with existing experimental data taken in the expansion plume. The computational results are employed to assess the effect of varying the mass-flow rate on the terminal state of the gas. In addition, the effect of including the background chamber pressure measured in the experimental vacuum facility is investigated and found to be significant.
RF sputter-deposited aluminum-oxide films as high quality artificial tunnel barriers

We report on the results of fabricating artificial tunnel barriers by the simple method of direct sputtering of an aluminum-oxide (Al 2 O 3 ) target. These barriers have been studied by preparing tunnel junctions of the form: Cu/AlOx/C.E. , with aluminum-oxide layers ranging in thickness from 8 to 20 A and counter-electrodes (C.E.) of Cu, Pb and PbBi. We have found that barriers with exceptionally large effective barrier heights, in excess of 2eV, and low zero-bias conduction, less than 0.4% leakage, can be reliably obtained by this method. We discuss the fabrication of these barriers and the systematics of both the effective (WKB) barrier shape, and superconducting and normal-state tunneling characteristics as a function of the measured barrier film thickness. X-ray photoelectron spectroscopy (XPS) studies on sputter-deposited aluminum-oxide films indicate the single composition, namely Al 2 O 3 . This method should prove universally applicable for depositing very high quality tunnel barriers.
Scattering Theorems for Acoustic Excitation of a Layered Obstacle by an Interior Point Source

Interesting scientific and technological applications motivate the study of scattering problems, where a layered scatterer is excited by a spherical acoustic wave generated by a point‐source located in its interior. The scatterer's core may be acoustically soft, hard, resistive, or penetrable. This paper initiates the investigation of scattering theorems, corresponding to the excitation of a layered scatterer by a point source in its interior. Reciprocity and general scattering theorems are established, relating the total fields and the corresponding far‐field patterns. The optical theorem, relating the scattering cross‐section with the field in the layer containing the source, is recovered as a corollary of the general scattering theorem. Furthermore, for a scatterer excited by a spherical and a plane wave, mixed scattering theorems are derived. Numerical implementations of the optical theorem in concrete scattering applications are analyzed.
Model predictions of coastal winds in a small scale

Details of surface winds across a flat and non-curved coastline have been considered, mostly in the 1–10 km scale, by looking at some published observed cases and simulating with a high-resolution numerical model. Stability conditions were emphasized by having the land and sea at slightly different temperatures, but sea breeze conditions were excluded. A warm surface generally enhances momentum transfer and wind speed, and reduces the cross-isobar angle. This transforms to rapid acceleration and downstream veering of offshore winds as they enter a warm, smooth sea. Cold sea, on the other hand, strongly inhibits vertical momentum transfer. This leads to offshore winds temporarily backing downstream off the coast, accelerating only slowly and even decreasing in speed in some cases. These observed facts were well simulated by the model. Onshore flow on to cold land brought along rapid deceleration and strong inland backing of winds. The deceleration was weaker and more gradual over warm land with downstream veering instead. Smaller geostrophic wind speed accentuated these and all other stability effects as the wind shears then were weaker relative to the buoyancy effects (i.e. the absolute values of the local Richardson numbers were larger). For large-scale winds along the shore with land on the right, the induced coastal convergence and rising motion appears only above about 100 m height in the cold sea simulations (typical of early summer). Below, there is divergence and hence relatively weak coastal wind. The case is the opposite for winds with land on the left (e.g. westerlies along a south coast): then the coastal surface winds are relatively strong along a cold sea. For a warm sea (typical of autumn) these low-level features disappear and coastal 10 m winds tend to be close to the geostrophic wind in speed and direction for all onshore directions.