Miracle-dz/UniFAR-FTUs huggingface dataset:
Secondary flow and roll cells interaction in high-aspect-ratio rotating turbulent duct flows

End-wall effects for high aspect ratio (AR) turbulent duct flows under moderate spanwise rotation are investigated using Reynolds-Averaged Navier–Stokes (RANS) calculations with a Reynolds stress turbulence closure model. It is shown that despite an important uniformisation of the mean streamwise flow compared to the non-rotating case, the channel flow solution (AR = ∞) is not recovered in practical high AR ducts used in experiments. The unavoidable end-wall generated secondary flow causes transverse advection which is capable of altering the mean velocity profile, even for AR as high as 22. In addition, for Re = 40,000 and Ro = 0.22, persistent longitudinal roll cells are found in the RANS solutions. The results suggest that their interaction with the secondary flow may challenge the prospect of formally reaching a steady, streamwise invariant regime in actual rotating duct experiments.
Spectra of Hercules X-1 near a turn-on in the 35 day cycle

X-ray spectra for Her X-l are presented for times before, during, and after a turn-on in the 35 day on-off cycle, as well as during an anomalous dip in the X-ray intensity. All four spectra are well represented by a power law of number index approximately . 9 with a high energy cutoff near 20 keV. However, the column density of cold matter along the line of sight as estimated by the low energy cutoff varies substantially among the four intervals. The low level flux present prior to turn-on does not pulse and shows very little low energy absorption, in contrast to the X-rays observed during the turn-on and the anomalous dip. It seems likely that the pre-turn-on flux is composed of X-rays scattered into the line of sight by material away from the accretion disk.
Active galactic nuclei flicker: an observational estimate of the duration of black hole growth phases of ∼105 yr

We present an observational constraint for the typical active galactic nucleus (AGN) phase lifetime. The argument is based on the time lag between an AGN central engine switching on and becoming visible in X-rays, and the time the AGN then requires to photoionize a large fraction of the host galaxy. Based on the typical light travel time across massive galaxies, and the observed fraction of X-ray selected AGN without AGN-photoionized narrow lines, we estimate that the AGN phase typically lasts 10 5 years. This lifetime is short compared to the total growth time of 10 7 10 9 years estimated from e.g. the Soltan argument and implies
Exact results for a two-dimensional one-component plasma on a sphere

Résumé. 2014 Pour étudier le modèle OCP du plasma classique à deux dimensions, nous proposons de placer les particules à la surface d’une sphère. Pour une valeur particulière de la température To la fonction de partition ainsi que les fonctions de distribution peuvent être calculées explicitement. A cette température la limite thermodyna-mique de ce système coïncide avec celle du système plan. Abstract. 2014 In order to study the properties of the two-dimensional classical one-component plasma, we propose to confine the particles to the surface of a sphere. For a special value To of the temperature, the partition and the distribution function can be calculated explicitly. The thermodynamic limit of this system coincides, for T = To, with the one obtained previously for a planar system.
Ground emitter localization via fusing terrain map and DOA measurements using two miniature UASs

This paper presents an emitter localization technique based on the fusion of Direction of Arrival (DOA) measurements obtained from two miniature unmanned aerial systems (UAS) and the terrain map of the interested area. The system's objective is to localize an emitter distributed in an area with 2000m radius in real time and the localization error is less than 100m with 95% confidence. In the system, each UAS is equipped with a three-element smart antenna for scanning the desired frequency band, calculating the received signal's spectrum signature and estimating the emitter's elevation and azimuth DOA. The received signal's DOA, spectrum signature, UAS position, and the time that the signal is received (calculated with respected to the pulse per second (PPS) signal of global positioning system (GPS)) are transmitted to the ground control station. At the ground control station, the DOA coming from the two UAS are aligned using the received signal's spectrum signature and time stamp, and then fused with the UAS position and terrain map to localize the emitter. This paper is focused on the localization scheme including the DOA estimation and emitter localization based on data fusion. The simulation conducted shows that azimuth DOA error (about 1.5°) is much smaller than elevation DOA error (about 5°), and the achieved localization error is less than 100m in most cases when the UAS and the emitter are located in an area with radius of 2000m.
A Highly Configurable Vortex Initialization Method for Tropical Cyclones

AbstractA highly configurable vortex initialization methodology has been constructed in order to permit manipulation of the initial vortex structure in numerical models of tropical cyclones. By using distinct specifications of the flow in the boundary layer and free atmosphere, an array of parameters is available to modify the structure. A nonlinear similarity model that solves the steady-state, height-dependent equations for a neutrally stratified, axisymmetric vortex is solved for the boundary layer flow. Above the boundary layer, a steady-state, moist-neutral, hydrostatic and gradient wind balanced model is used to generate the angular momentum distribution in the free atmosphere. In addition, an unbalanced mass-conserving secondary circulation is generated through the assumption of conservation of mass and angular momentum above the boundary layer. Numerical simulations are conducted using a full-physics mesoscale model to explore the sensitivity of the vortex evolution to different prescriptions of t.
NUCLEAR SPIN-LATTICE RELAXATION IN METALS

The nuclear spin-lattice relaxation time, T/sub 1/, was measured in the range of 1.1 to 4.2 deg K for the metals lithium, sodium, aluminum, and copper. A combination of nuclear magnetic resonance at fixed frequency and adiabatic variation of the magnetic field was used to measure T/sub 1/ as a function of field between zero and one thousand gauss. At fields of between one hundred and one thousand gauss T/sub 1/ is independent of magnetic field and inversely proportional to temperature in agreement with theory. The experimental values of the relaxation time multiplied by absolute temperature in sec deg K are 44 plus or minus 2.0 for Li/sup 7/; 5.1 plus or minus 0.3 for Na/sup 23/; 1.80 plus or minus 0.05 for Al/sup 2 1.27 plus or minus 0.07 for Cu/sup 63/. These values are in good agreement with previous experimental data at room temperature and above. At fields comparable with the nuclear magnetic dipole-dipole fields, T/sup 1/ is a function of applied field. The theory of relaxation in low fields is presented in an elementary form. Qualitative agreement with theory is obtained for Al/sup 27/ and Cu/sup 63/; detailed agreement is obtained for Li/sup 7/ and Na/sup 23/. more » (auth)« less
Global distribution of atmospheric waves in the equatorial upper troposphere and lower stratosphere: COSMIC observations of wave mean flow interactions

[1] Temperature profiles derived from Constellation Observing System for Meteorology, Ionosphere and Climate Global Positioning System Radio Occultation satellite constellation data are used to study equatorial gravity wave potential energy associated with waves having vertical wavelengths of less than 7 km and their interaction with the background quasi-biennial oscillation (QBO) wind. The data are binned into grids of size 20° in longitude and 5° in latitude. Results show evidence of vertically propagating convectively generated gravity waves interacting with the background mean flow. Enhancements in potential energy around the descending 0 m s−1 QBO eastward shear phase line are observed. Equatorially trapped Kelvin waves and Mixed Rossby Gravity Waves with zonal wave numbers s ≤ 9 are obtained by bandpass filtering wave number-frequency temperature spectra. Their temporal, spatial and vertical structures, propagation and wave-mean flow interactions are examined with respect to the background mean flow. Equatorial waves observed by COSMIC are compared with those seen in OLR data, with differences discussed.
Visceral Adipose Tissue Assessment Enhances the Prognostic Value of GLIM Criteria in Patients with Gastric Cancer Undergoing Radical Gastrectomy after Neoadjuvant Treatment

Background: The Global Leadership Initiative on Malnutrition (GLIM) criteria has been recently published for diagnosing malnutrition in adults. However, the validity of the GLIM criteria has not been well-established in patients with gastric cancer (GC) treated with neoadjuvant treatment (NT) followed by radical gastrectomy. The present study aimed to explore the prognostic value of GLIM-defined malnutrition before NT and after NT in GC patients and to investigate whether additional visceral adipose tissue (VAT) assessment could improve the predictive power of the GLIM criteria for NT-related adverse events (AEs) and long-term survival. Methods: GC patients who underwent radical surgery after NT from June 2016 to June 2020 were enrolled in this study. The cross-sectional areas of total skeletal muscle (TSM) and VAT were measured using computed tomography (CT) before NT and after NT. GLIM-defined malnutrition was diagnosed using the two-step approach, including nutritional risk screening and diagnostic assessment. Low VAT was also added to the diagnosis of malnutrition in this study. The predictive value of these malnutrition diagnoses for NT-related AEs, and long-term survival was evaluated in GC patients. Results: A total of 182 GC patients were included in this study, of which 66 (36.3%) patients before NT and 55 (30.2%) patients after NT were diagnosed with GLIM-defined malnutrition, respectively. In addition to GLIM-defined malnutrition, 54 (29.7%) patients had additional low VAT before NT, and 39 (21.4%) patients had additional low VAT after NT. GLIM-defined malnutrition alone before NT was not associated with NT-related AEs in GC patients. The addition of low VAT to GLIM-defined malnutrition led to a significant predictive value for NT-related AEs. Furthermore, GLIM-defined malnutrition before NT and after NT were both identified as independent risk factors for overall survival (OS) and disease-free survival (DFS). The combination of low VAT and GLIM-defined malnutrition showed a higher hazard ratio for the prediction of OS and DFS both before NT and after NT. Conclusions: The addition of VAT assessment using CT improved the predictive value of GLIM-defined malnutrition for NT-related AEs and long-term survival in GC patients treated with NT followed by radical gastrectomy, which further supports the prognostic importance of assessing adipose tissue simultaneously during the routine nutritional assessment in patients with cancer.
Assessment of the water supply to Mediterranean heavy precipitation: a method based on finely designed water budgets

A major ingredient for Mediterranean Heavy Precipitating Events (HPEs) is the low‐level moisture transport towards the coast. This paper proposes a methodology allowing a spatially and temporally continuous study of the water supply to Mediterranean HPEs. It is based on water budgets computed from mesoscale numerical simulation outputs. The method is applied on four typical HPEs over Southeastern France. It allows to identify and assess quantitatively the contributions of local Mediterranean and remote African and Atlantic moisture sources.
Synthetic aperture ladar resolution through turbulence

The theory is developed for the resolution of a coherent optical synthetic aperture imaging system viewing an object through turbulence. The turbulence induces wave distortions that in turn induce errors in the phase history data collected over the synthetic aperture. The image effects of the phase history errors are space-variant and include broadening of the point spread function as well as geometric distortions. The effect of wave distortions on the intensity image impulse response is related to the usual wave structure function (sum of the log-amplitude and phase structure functions) at the synthetic aperture center frequency. The turbulence-induced limit on resolution is determined for synthetic apertures or any size, without restriction on the size of the real sampling aperture. The results have commonalties to the well-known limit on the resolution of incoherent real aperture imaging systems. A relationship is derived for the resolution of an optical synthetic aperture image forming system relative to the resolution of a passive optical real aperture image forming system viewing through the same inhomogeneous medium.
State-of-the-Art Overview of Boiling and Two-Phase Flows in Microchannels

A state-of-the-art overview of recent work on boiling and two-phase flows in microchannels are reviewed, focusing primarily on the high points of recent developments. The topics covered include critical heat fluxes and their prediction in microchannels, new two-phase flow pattern maps, flow regimes and visualization in microchannels, boiling phenomena and flow instabilities in multi-microchannel cooling elements, flow boiling prediction methods specifically for microchannels and their comparison to data, trends in flow boiling data in microchannels and mechanisms that may be responsible for the seemingly divergent trends, and two-phase pressure drops in microchannels.
BRST cohomologies for non-critical strings

The BRST cohomologies of non-critical massive string models are analysed in detail in the range of dimensions 1<d<26. The classical theorems on vanishing of Dolbeaut type and relative cohomologies are proved. The no-ghost theorem is proved in the same range of dimensions. It is also shown that the BRST complex of the massive string model is a resolution of the non-critical Nambu-Goto string in all spacetime dimensions 1<d<25.
Coupled electron–hole quantum well structure: mass asymmetry and finite width effects

We investigate the role of many-body correlations in determining the ground-state behaviour of the coupled electron–hole quantum well structure by including the mass asymmetry and the finite width of wells. The correlations (both the intra- and inter-well) are treated beyond the static local-field theories by employing the dynamical self-consistent mean-field approximation of Hasegawa and Shimizu. The mass asymmetry is seen to introduce a marked change in the ground state of the electron–hole system as compared to the recent corresponding results on the mass-symmetric electron–hole bilayer. First, the critical density for the liquid–Wigner crystal phase transition is greatly enhanced (e.g., by a factor of about 4 for a GaAs/GaAlAs based system). Second, there is a change in the role played by the electron–hole correlations. The Wigner crystal phase is now found to be stable below a critical density only at sufficiently large separation between the wells. The build-up of electron–hole correlations with diminishing inter-well spacing tends to favour the charge-density-wave phase over the Wigner crystal state, with the result that the former always prevails in the sufficiently close approach of wells. This result differs strikingly from the corresponding studies on the mass-symmetric system, since the electron–hole correlations are predicted here to always support, at sufficiently small well spacing, the Wigner crystal phase below a critical density and the charge-density-wave phase at relatively higher densities. Further, we find that the inclusion of the finite width of layers results in lowering of the critical density for Wigner crystallization.
Tuning the thermal conductivity of polymers with mechanical strains

Received 8 January 2010; revised manuscript received 12 April 2010; published 28 May 2010The low thermal conductivity of polymers limits their heat spreading capability, which is one of the majortechnical barriers for the polymer-based products, especially electronics, such as organic light emitting diodes.It is highly desirable to enhance the thermal conductivity of polymer materials including polymer composites.Mechanical stretching could align polymer chains which are intrinsically low-dimensional material that couldhave very high thermal conductivity and thus enhancing the thermal conductivity of polymers. In this work, theall-atom model molecular-dynamics simulation is conducted to investigate the tuning of polymer thermalconductivity using mechanical strains. The simulation results show that the thermal conductivity of polymersincreases with the increasing strain and the enhancement is larger when the polymer is stretched slower.Molecular weight also affects the thermal conductivity under the same stretching condition. More importantly,the thermal-conductivity enhancement could be exponentially ﬁtted with the orientational order parameterwhich describes the chain conformation change. This study could guide the development of advanced recon-ﬁgurable and tunable thermal management technologies.DOI: 10.1103/PhysRevB.81. 174122 PACS number s : 65.60. a, 66.70. Hk, 68.35. bm
Field-emitted current necessary for cathode-initiated vacuum breakdown

Energy exchange processes occurring at microprojections on a cathode surface are analysed, and expressions are obtained for the critical current necessary to produce thermal instability in projections of different geometries leading to a vacuum arc. The effect of energy transfer due to lattice electrons (Nottingham effect) is included in the analysis, and it is found that when this effect is included the critical current decreases by a factor of 2·8 in the case of a conical microprotrusion and by a factor of 1·2 in the case of a cylindrical microprotrusion.
Experiments on standing bubbles in a vertical pipe

We present a series of laboratory experiments in which a steady stream of air is supplied through a small hole in the wall of a vertical pipe of rectangular cross-section down which there is a steady flux of water. For a range of liquid flow rates, the air forms a steady standing bubble whose nose is attached to the point of air supply. The steady bubble sheds a flux of much smaller air bubbles at its base, located downstream of the air injection point. The minimum liquid speed for which steady standing bubbles develop occurs at a particular Froude number of the liquid flow, Frd = U/$/sqrt{\it gd}$ = 0.38, where U is the upstream speed, g the acceleration due to gravity and d the width of the cell. These trapped bubbles are distinct from the freely rising Taylor bubble, in that the Froude number at the nose is variable. Also, on a length scale greater than that influenced by surface tension, we find that the bubble nose asymptotes to a cusp-like shape, with an angle that decreases with Frd. We show that numerical solutions of the potential flow equations replicate the bubble shape and angle of the cusp, which appear independent of the gas flux. We also find that there is a minimum gas flux for which these standing bubbles develop. As the gas flux decreases below this threshold, the standing bubbles become unstable and, instead, a much shorter oscillating bubble develops. This produces a wake which has similarities with that formed downstream of a cylinder in a confined channel, but which also carries bubbles downstream. We also find that with sufficiently small gas flux, no bubble develops. For liquid flow rates smaller than the critical value, Frd < 0.38, we find that the bubbles become unstable and detach from the injection point and rise up the tube.
The stable regulator problem and its inverse

This paper provides a detailed survey and extension of certain properties of the stable regulator problem: determine \min\inf{u} \int\min{0}\max{\infty} x'Qx + u'u dt subject to \dot{x} = Fx + Gu; x(0) = x_{0}; \liminf{t \rightarrow \infty} x(t) = 0 where Q is not necessarily sign definite. First, equivalence conditions recently given by Willems for the existence of the minimum are extended to include statements in terms of the Hamiltonian matrix and spectral factorization. This provides a precise relation between the time-domain and frequency-domain solutions to the problems. Second, the inverse problem of whether a given feedback u = -Kx is optimal for some Q is easily resolved, as is the redundancy problem of distinct Q 1 and Q 2 , resulting in the same optimal control.
Questions and challenges for the new psychology of reasoning

In common with a number of other authors I believe that there has been a paradigm shift in the psychology of reasoning, specifically the area traditionally labelled as the study of deduction. The deduction paradigm was founded in a philosophical tradition that assumed logicality as the basis for rational thought, and provided binary propositional logic as the agreed normative framework. By contrast, many contemporary authors assume that people have degrees of uncertainty in both premises and conclusions, and reject binary logic as a workable normative system. I discuss a number of questions and challenges for this new psychology of reasoning, including the following: (a) Do we need an alternative normative system, such as Bayesianism, for the new paradigm? (b) Is there any longer a clear distinction between the study of deductive and inductive reasoning, the latter having its own tradition and literature? (c) Precisely how is the integrated study of reasoning and decision making facilitated by the new paradigm? (d) What difficulties with dual-processing approaches need to be resolved, if they are to take us forward?
FINITE ELEMENT MODELLING OF THE TENSILE STRAIN SOFTENING BEHAVIOUR OF PLAIN CONCRETE STRUCTURES

The localized strain softening behaviour of concrete has been modelled by two approaches: (i) the stiffness degrading model based on the total stress‐strain constitutive relationship, and (ii) the tangent softening model based on the incremental stress‐strain relationship. The models are implemented using a new softening initiation criterion proposed for application in multi‐dimensional finite element analysis. Parametric analyses on plain concrete beams, tested experimentally by other researchers, have been carried out to investigate the required numerical efforts, the mesh objectivity, and the energy dissipation characteristics of the structures. The stiffness degrading model is very stable even when applied with relatively coarse finite element meshes. However, the computational demand of this model is relatively high. The combination of a total stress‐strain constitutive relationship to compute the element responses, and an incremental relationship to formulate the stiffness matrix, appears to be computationally efficient and stable, provided that adequately refined finite element mesh is used to model the structure.