Miracle-dz/UniFAR-FTUs huggingface dataset:
Structure of Velocity Space‐Time Correlations in a Boundary Layer

Space‐time correlations of longitudinal velocity fluctuations have been measured in a turbulent boundary layer, with and without frequency filtering. Celerities, relative to various fluctuations scales, are defined as partial derivatives of the isocorrelation curves with respect to both space separation and time delay. An example of the introduction of these celerities into the equations of motion is given for a simple case. The variation of these celerities with respect to fluid velocity is examined as a function of fluctuation scales and of distance to the wall. As a complement to the study of the effect of longitudinal space separation, the effect of space separation orthogonal to the wall resulting in a time delay corresponding to the maximum value of the correlation coefficient has been determined for various filtering frequencies.
Eigenfunction Expansions Associated with Unitary Irreducible Representations of SU(1,1)

The noncompact group SU(1,1) has three types of parametrizations associated with the three classes of one-parameter subgroups. Each of them gives rise to an expansion into matrix elements which are eigenfunctions of the differential operator associated with the Casimir invariant. The two cases related to noncompact subgroups are solved using some previous results on the generalized eigenvectors of the noncompact generators of SU(1,1).
Figure of merit of diamond power devices based on accurately estimated impact ionization processes

Although a high breakdown voltage or field is considered as a major advantage of diamond, there has been a large difference in breakdown voltages or fields of diamond devices in literature. Most of these apparently contradictory results did not correctly reflect material properties because of specific device designs, such as punch-through structure and insufficient edge termination. Once these data were removed, the remaining few results, including a record-high breakdown field of 20 MV/cm, were theoretically reproduced, exactly calculating ionization integrals based on the ionization coefficients that were obtained after compensating for possible errors involved in reported theoretical values. In this compensation, we newly developed a method for extracting an ionization coefficient from an arbitrary relationship between breakdown voltage and doping density in the Chynoweth's framework. The breakdown field of diamond was estimated to depend on the doping density more than other materials, and accordingly required to be compared at the same doping density. The figure of merit (FOM) of diamond devices, obtained using these breakdown data, was comparable to the FOMs of 4H-SiC and Wurtzite-GaN devices at room temperature, but was projected to be larger than the latter by more than one order of magnitude at higher temperatures about 300 °C. Considering the relatively undeveloped state of diamond technology, there is room for further enhancement of the diamond FOM, improving breakdown voltage and mobility. Through these investigations, junction breakdown was found to be initiated by electrons or holes in a p −-type or n −-type drift layer, respectively. The breakdown voltages in the two types of drift layers differed from each other in a strict sense but were practically the same. Hence, we do not need to care about the conduction type of drift layers, but should rather exactly calculate the ionization integral without approximating ionization coefficients by a power function of electric field as often done in Si devices. In order to facilitate this approach, we developed a method for simplifying the ionization integral, which method, together with the aforementioned method for extracting ionization coefficients, will help to promote the study on breakdown phenomena of all semiconductors.
Wakes behind a prolate spheroid in crossflow

Abstract Viscous laminar flow past a prolate $(L/ d= 6)$ spheroid has been investigated numerically at seven different Reynolds numbers; $\mathit{Re}= 50, 75, 100, 150, 200, 250$ and $300$. In contrast to all earlier investigations, the major axis of the spheroid was oriented perpendicular to the free stream flow. As expected, the flow field in the wake showed a strong resemblance of that observed behind a finite-length circular cylinder, yet had features observed in the axisymmetric wake behind a sphere. The following different flow regimes were observed in the present computational study: (i) steady laminar flow with massive flow separation and symmetry about the equatorial and the meridional planes at $\mathit{Re}= 50$; (ii) steady laminar flow with massive flow separation and symmetry about the equatorial and the meridional plane at $\mathit{Re}= 75$, but the flow in the equatorial plane did no longer resemble the steady wake behind a circular cylinder; (iii) unsteady laminar flow with Strouhal number $0. 109$ and symmetry about the equatorial plane at $\mathit{Re}= 100$; (iv) unsteady laminar flow with two distinct frequencies and without any planar symmetries at $\mathit{Re}= 200$; (v) transitional flow with a dominant shedding frequency $\mathit{St}= 0. 151$ and without any spatial symmetries at $\mathit{Re}= 300$. For all but the two lowest $\mathit{Re}$ hairpin vortices were alternately shed from the two sides of the spheroid and resulted in a ladder-like pattern of oppositely oriented vortex structures, in contrast with the single-sided shedding in the wake of a sphere. The contour of the very-near-wake mimicked the shape of the prolate spheroid. However, $15d$ downstream the major axis of the wake became aligned with the minor axis of the spheroid. This implies that an axis switching occurred some $10d$ downstream, i.e. the cross-section of the wake evolved such that the major and minor axes interchanged at a certain downstream location. This peculiar phenomenon has frequently been reported to arise for elliptical and rectangular jets, whereas observations of axis switching for asymmetric wakes are scarce.
Liquid crystal birefringence for millimeter wave radar

Abstract Many liquid crystals are found to have relatively high birefringence (Δn) values in the microwave and millimeter wave regions, as calculated from the phase shift induced by their reorientation by magnetic or electric fields. At 30 GHz, Δn values were obtained in the range of 0.08 to 0.18 for eleven liquid crystal mixtures of various types. The most favourable liquid crystal structures for high millimeter wave birefringence are highly conjugated rod-like molecules containing biphenyl, terphenyl, phenylpyrimidine, biphenylpyrimidine, and tolane groups in nematics of positive dielectric anisotropy (Δe). However, other liquid crystal structures including Schiffs base, azoxybenzene, and aromatic ester groups also have substantial birefringence, including nematics with negative and crossover Δe, as well as cholesteric nematics. The Δn varied only slightly at different frequencies of microwave millimeter wave in the 15–94 GHz range. Studies on magnetic and electrical field liquid crystal orientation in .
Complexity matching in neural networks

In the wide literature on the brain and neural network dynamics the notion of criticality is being adopted by an increasing number of researchers, with no general agreement on its theoretical definition, but with consensus that criticality makes the brain very sensitive to external stimuli. We adopt the complexity matching principle that the maximal efficiency of communication between two complex networks is realized when both of them are at criticality. We use this principle to establish the value of the neuronal interaction strength at which criticality occurs, yielding a perfect agreement with the adoption of temporal complexity as criticality indicator. The emergence of a scale-free distribution of avalanche size is proved to occur in a supercritical regime. We use an integrate-and-fire model where the randomness of each neuron is only due to the random choice of a new initial condition after firing. The new model shares with that proposed by Izikevich the property of generating excessive periodicity, and with it the annihilation of temporal complexity at supercritical values of the interaction strength. We find that the concentration of inhibitory links can be used as a control parameter and that for a sufficiently large concentration of inhibitory links criticality is recovered again. Finally, we show that the response of a neural network at criticality to a harmonic stimulus is very weak, in accordance with the complexity matching principle.
Arithmetic means of subsequences

for n -* 20 , exists for almost all x} we shall say that almost all the subsequences of {sn} are summable (C, 1); if the limit of (1) does not exist for almost all χy we say that almost all the subsequences of isn} are not summable (C>1) (cf. [2]). These two cases are the all which may occur, since the existence set of the limit of (1) is homogeneous. If the limit of (1) exists only for x belonging to a set of the first category, it is called that nearly all the subsequences of {sn} are not summable (C,l). R. C. Buck and H. Pollard [ 2 ] proved the following theorem.
Interface induced inverse spin Hall effect in bismuth/permalloy bilayer

Inverse spin Hall effect has been investigated in bismuth(Bi)/permalloy(Py) bilayer films by using the spin pumping at room temperature. From the ferromagnetic-resonance-spectrum linewidth data, Bi is proved to be a good spin sink in our structure. We measured inverse spin Hall voltage and conductance of the Bi/Py bilayer and found that the inverse spin Hall current, Ic, decreases with increasing the Bi thickness, which is in contrast to the former understanding in similar bilayer systems, e.g., Pt/Py. We constructed a model to explain the thickness dependence of Ic quantitatively, in which spin transport modulation near Bi/Py interface is considered.
Swash overtopping a truncated plane beach

Swash on a plane beach is modelled by using a solution of the shallow-water equations due to Shen & Meyer (1963). The equations are used in a form appropriate for a plane at a finite angle to the horizontal. The beach is cut-off at a level below that of the maximum run-up, and the water is taken to fall freely over the end of the beach. An explicit solution is found which permits evaluation of the overtopping flow and total volume for one swash event.
Refined similarity hypotheses for turbulent velocity and temperature fields

The refined similarity hypothesis of Kolmogorov [J. Fluid Mech. 13, 82 (1962)] is extended to a scalar field. These hypotheses are tested using measurements in a circular jet and the atmospheric surface layer. Over a significant part of the inertial range, statistics of the normalized stochastic variables for velocity and temperature indicate a dependence on the separation r. This dependence is also quantified through the probability density functions of the stochastic variables and the correlation between the velocity (or temperature) increment and the local energy (or temperature) dissipation rates. Probability density functions of the stochastic variables are conditioned on the local Reynolds number Rer based on r and the local energy dissipation rate. These functions depend on Rer when the latter is small and are approximately universal when Rer is very large. This behaviour is consistent with the refined similarity hypothesis. There is however a slight difference between the shapes of the conditional.
The relative spatial distributions of high- and low-luminosity galaxies toward Coma

The relative spatial distributions of low- and high-mass galaxies which lie in a field in the direction of the Coma Supercluster are investigated. Three tests are used to compare the distributions of high-luminosity and low-luminosity galaxies in the field: correlation functions, nearest neighbor distributions, and local density environments. All three tests indicate that the low-luminosity galaxies are significantly less confined to the structure defined by the luminous galaxies than are the luminous galaxies themselves. Several galaxies in the low-luminosity subsample are within voids. These findings lend support to various models for the formation of large-scale structure that include biased galaxy formation. In particular, the ratio of the amplitudes of the correlation functions for dwarfs and giants agrees closely with the predictions of the cold dark matter models of White et al. (1987). 54 refs.
Prediction of the bubble nucleation rate in a quasi-stable cavitating nozzle using 2D computational fluid dynamics and enhanced classical nucleation theory

Most of the numerical studies of the cavitation process available were simulated based on the Rayleigh-Plesset equation, which has a presumed value for the number of bubble nuclei in the domain. However, in the computational domain for most cases, the bubble nuclei density varies, depending on the hydrodynamics and different bubble nucleation rates. Therefore, the modeling of the bubble nucleation rate based on the number of molecules required to form a critical cluster, which is affected by the hydrodynamics in the domain, is one of the challenges that must be overcome for bubble nuclei density prediction. In this work, an enhanced Classical Nucleation Theory (CNT) model was written as in-house code for integration in Computational Fluid Dynamics (CFD) to estimate the water vapor bubble nucleation rate across a quasi-stable cavitating flow nozzle. The enhanced CNT model included microscopic factors that specifically address water vapor bubble nucleation. Because these factors vary in the radial direction, this work was extended into the 2D domain to estimate the bubble nucleation rate in both the axial and the radial directions. The bubble nucleation rate was estimated through various numbers of molecules (depending on the hydrodynamics in the domain) required to form a critical cluster. The Population Balance Model was used to estimate the bubble nuclei density based on the bubble nucleation rate. The simulated results indicated that the bubble nucleation rate was highest at the throat of the nozzle, especially near the wall of the nozzle. Thus, a higher bubble nuclei density was found near the wall after the throat of the nozzle.
Scattering of field-aligned beam ions upstream of Earth's bow shock

Abstract. Field-aligned beams are known to originate from the quasi-perpendicular side of the Earth's bow shock, while the diffuse ion population consists of accelerated ions at the quasi-parallel side of the bow shock. The two distinct ion populations show typical characteristics in their velocity space distributions. By using particle and magnetic field measurements from one Cluster spacecraft we present a case study when the two ion populations are observed simultaneously in the foreshock region during a high Mach number, high solar wind velocity event. We present the spatial-temporal evolution of the field-aligned beam ion distribution in front of the Earth's bow shock, focusing on the processes in the deep foreshock region, i.e. on the quasi-parallel side. Our analysis demonstrates that the scattering of field-aligned beam (FAB) ions combined with convection by the solar wind results in the presence of lower-energy, toroidal gyrating ions at positions deeper in the foreshock region which are magnetically connected to the quasi-parallel bow shock. The gyrating ions are superposed onto a higher energy diffuse ion population. It is suggested that the toroidal gyrating ion population observed deep in the foreshock region has its origins in the FAB and that its characteristics are correlated with its distance from the FAB, but is independent on distance to the bow shock along the magnetic field.
On the Effect of Practice and Motivation on the Threshold of Audibility

The thresholds of audibility for 100 and for 1000 cps have been measured on five groups of originally naive listeners by various experimental techniques. All the experiments showed improvement of the threshold with practice. The improvement was greater at 100 cps than at 1000 cps. Pretraining at 1000 cps did not affect the threshold change at 100 cps. The improvement of the threshold with practice was enhanced considerably by reward and feedback.
Monitoring of UV spectral irradiance at Thessaloniki (1990–2005): data re-evaluation and quality control

Abstract. We present a re-evaluation and quality control of spectral ultraviolet irradiance measurements from two Brewer spectroradiometers operating regularly at Thessaloniki, Greece. The calibration history of the two instruments was re-examined and data flaws were identified by comparing quasi synchronous measurements. Analysis of the sensitivity of both instruments to variations of their internal temperature revealed that they have temperature coefficients of different sign. These coefficients exhibit small variability during the 15-year period. Using averaged temperature coefficients, we corrected both datasets. Corrections were applied for the angular response error using two different approaches depending on the availability of required ancillary data. The uncertainties associated with the measurements have been estimated and presented. Finally, the two datasets are compared using ratios of irradiance integrals at various bands in the UV, in order to assess any dependencies on the internal instrument temperature, solar zenith angle and wavelength.
Computational and Experimental Studies of Unsteady Viscous Nozzle Flows

The present paper describes the numerical and experimental results on unsteady nozzle flows induced by nonstationary shock waves. The two-dimensional Navier-Stokes equations are numerically solved using the upwind TVD finite-difference scheme of the Harten-Yee type. For the purpose of computational visualization of shock waves in transient nozzle starting process, computer shadowgraphs are developed based on the principle of the optical shadowgraph. Visualization experiments employing a conventional shock tube are also performed. Comparison of numerical and experimental results shows satisfactory agreement. Furthermore, the steady flow establishment process around an airfoil model installed inside the nozzle is numerically investigated. The simulated results successfully reveal the unsteady viscous flow structure around the model.
Life insurance for insulin-dependent diabetics

Abstract This paper presents a study of the mortality of insulin-dependent diabetics diagnosed before age 31. The analysis includes the effect of various covariates on the mortality and on the risk of developing diabetic nephropathy, a serious renal complication associated with diabetes. The results show that it is the risk of developing nephropathy combined with very high mortality rates of patients with nephropathy which are the main reasons for the excess mortality usually experienced among insulin-dependent diabetics. The results are used to provide examples of the cost of individual life and group life insurance for diabetics who, at the time of issue of insurance, show no sign of diabetic nephropathy.
Accurate Determination of Input Parameters of Rectangular Microstrip Patch Antenna on Thick Substrate and Comparision of Several Models

Theoretical models like standard cavity model, multiport cavity model (MCM), MOM-based commercial software, and Ensemble do not provide accurate results on the resonance frequency, input impedance, and bandwidth for the rectangular patch on the thick substrate (h > 0.05 λ g ). This paper reports an improved form of the cavity model called the modified Wolff model (MWM) that computes accurately these parameters of the rectangular patch on the thick substrate up to the substrate thickness 0.229 λ g . We also compare all of these models against the experimental results obtained from the several sources. The MWM comes out as the most accurate model for the computation of input parameters of the rectangular patch both on the thin and thick substrates also having anisotropy.
Which Words Spell “Almost Nilpotent?”

A class of words is introduced with the property that a finite group satisfying an identity of length N defined by a member of this class is nilpotent-of- N -bounded-class-by- N -bounded-exponent. Conversely, we see that this class of words characterises such groups; a group which is nilpotent-of-class- c -by-exponent-at-most- c , satisfies an identity from this class whose length is c -bounded. Related results are discussed.
Complete Stresses and Displacements in a Cross-Anisotropic Half-Space Caused by a Surface Vertical Point Load

AbstractThe elastic solution of a loaded cross-anisotropic half-space is dependent on the type of anisotropy that is governed by whether the characteristic equation has real and distinct or equal or complex roots. Most previous solutions have been for the case of real and distinct roots and most have also been incomplete. This work presents complete expressions for all stresses and displacements in a homogeneous, linearly elastic cross-anisotropic half-space caused by a surface vertical point load for all three types of anisotropy, which are believed to be more compact and simpler than those given by the only currently existing complete solution. In the present work, only 38 intermediate parameters need to be calculated in order to define all stresses and displacements as compared with the 62 parameters required in the other existing complete solution. Also, an important discovery is made: the surface settlement of a half-space is given by the same formula irrespective of the type of anisotropy, and this .
Slowly Accreting Neutron Stars and the Origin of Gamma-Ray Bursts

Old, isolated neutron stars accrete interstellar gas at a rate of about 10 to the 10th g/s. At this slow accretion rate, the interior temperature is too low for thermonuclear reactions to proceed, and the hydrogen burns by pycnonuclear reactions. The resulting helium then burns through pycnonuclear triple-alpha and (alpha, gamma) channels until it is exhausted. As the pressure increases under the weight of the accreted gas, the electron Fermi energy becomes large enough for electron capture to increase the neutron fraction in the nuclei. The layer of accreted gas can then become denser than the underlying crust, and the interface is susceptible to elastic Rayleigh-Taylor instability. A crust supported by relativistic electron degeneracy pressure is unstable when the fractional density decrease at the interface exceeds a critical value between 3 and 8 percent, depending upon the composition of the two layers. If the star has a magnetosphere, then this will be excited as well, producing a gamma-ray burst. If a substantial amount of the energy released is converted into heat locally, then the resulting temperature, roughly one billion K, may be hot enough to trigger thermonuclear reactions and raise the total energy release by a factor of about 30.more » Energetic and statistical implications of the model are critically examined, and some observable consequences are described. The model's sensitive dependence on poorly known pycnonuclear and thermonuclear reaction rates is emphasized. 52 refs.« less