Miracle-dz/UniFAR-FTUs huggingface dataset:
The Secular Evolution of Galactic Disks with a Star Formation Threshold: The Origins of Low Surface Brightness Spirals, Magellanic Irregulars, and Blue Compact Dwarfs

The long-term evolution of disk galaxies of extremely late morphological type is examined in relation to the possible dynamical effect of a star formation threshold in the interstellar gas. Although having common features such as high gas content, blue optical colors, and dominant dark matter, extremely late galaxies exhibit a remarkable diversity in their structure, ranging from low surface brightness disks and central bars to the centrally concentrated star-forming regions that characterize blue compact dwarf galaxies. I make the hypothesis that the observed structural variety has been caused by secular evolution processes taking place in the galactic disks, probably driven by some kind of viscosity. A simple model of the secular evolution of galactic disks is devised, and how the mass redistribution process depends upon the galaxy mass and density is examined. It is found that the existence of a threshold surface density of the gas disk, below which the star formation is heavily damped, has a profound effect on the viscosity-driven evolution of late-type galaxies, i.e., galaxies with a small mass and/or a low density. More massive and/or denser galaxies, corresponding to luminous high surface brightness galaxies (with a Hubble type of ~Scd and earlier), hardly suffer from this effect and are governed by a different regime of mass transport. The most important result found in the present extensive model calculation is that the "viscous" evolution model of galactic disks, coupled with the existence of a star formation threshold in the interstellar gas density, predicts the formation of gas-rich, low-mass galaxies that have a prominent central component at the present cosmological epoch. The most plausible candidates for such systems include blue compact dwarf galaxies and extremely late-type disk galaxies possessing a central bar.
Shock-Wave/Boundary-Layer Interactions in a Model Scramjet Intake

An air intake for a Mach 8 flight vehicle concept has been studied using large-eddy simulation with flow conditions corresponding to typical wind-tunnel tests. The flow contains several types of shock-wave/boundary-layer interaction for which large-eddy simulation has advantages over conventional Reynolds-averaged Navier-Stokes approaches. Laminar-to-turbulent transition was triggered using localized blowing trips in the first external ramp surface close to the intake leading edge. The trips lead to turbulent spots that propagate within an otherwise laminar flow, with a lateral spreading angle consistent with previous studies. The transitional/turbulent shock interaction near the. first compression corner was found to enhance the transition to turbulence, leading to a fully turbulent boundary layer after the interaction. Further downstream, a large separation zone forms due to the cowl-lip shock wave impinging on the vehicle-side boundary layer. Perturbations from the vehicle-side turbulent boundary layer were found to enter the cowl-side boundary layer. The final transition of this boundary layer occurred at the end of a separation bubble created by the first cowl-side compression ramp. Statistics for the turbulent How entering the combustor inlet show thick nonequilibrium turbulent boundary layers and trapped compression waves.
Turbulent Boundary Layer Under the Influence of Adverse Pressure Gradient

The paper deals with the experimental analysis of turbulent boundary layer at the flat plate for large value of Reynolds number equal Reθ ≈︁ 3000. The adverse pressure gradient generated by curvature of the upper wall corresponded to the case of pressure variation in axial compressor. The fully developed structure of turbulence was achieved by proper triggering of the boundary layer. The mean and turbulent flow‐fields were investigated with the use of hot‐wire technique while mean and instantaneous pressure fields were examined with piezoelectric transducers. The scaling and turbulence structure of fully developed turbulent boundary layer under the influence of adverse pressure gradient revealed the more pronounced contribution of outer region to the downstream development of turbulent boundary layer. (© 2009 Wiley‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A comparison between characteristics of atmospheric-pressure plasma jets sustained by nanosecond- and microsecond-pulse generators in helium

Power source is an important parameter that can affect the characteristics of atmospheric-pressure plasma jets (APPJs), because it can play a key role on the discharge characteristics and ionization process of APPJs. In this paper, the characteristics of helium APPJs sustained by both nanosecond-pulse and microsecond-pulse generators are compared from the aspects of plume length, discharge current, consumption power, energy, and optical emission spectrum. Experimental results showed that the pulsed APPJ was initiated near the high-voltage electrode with a small curvature radius, and then the stable helium APPJ could be observed when the applied voltage increased. Moreover, the discharge current of the nanosecond-pulse APPJ was larger than that of the microsecond-pulse APPJ. Furthermore, although the nanosecond-pulse generator consumed less energy than the microsecond-pulse generator, longer plume length, larger instantaneous power per pulse and stronger spectral line intensity could be obtained in the nanosecond-pulse excitation case. In addition, some discussion indicated that the rise time of the applied voltage could play a prominent role on the generation of APPJs.
Lead-free ceramics for pyroelectric applications

The use of lead-free materials has recently become a very important issue in environmental protection of the earth. Two groups of lead-free ceramics, (K0.5,Na0.5)NbO3 based (KNN) and Bi1−y(NaxK1−x)yTiO3 based (BNKT), were studied for their thermal, dielectric, and pyroelectric properties as candidates for pyroelectric sensor applications. The BNKT-based ceramic, [Bi0.5(Na0.94K0.05Li0.016)0.5]0.95Ba0. 05TiO3 (BNKLBT), shows excellent pyroelectric properties when compared with KNN-based ceramic and lead zirconate titanate. Its properties were measured as follows: pyroelectric coefficient p=360μC∕m2K, pyroelectric figure of merit of current, voltage, and detectivity Fi=221pm∕V, Fv=0.030m2∕C, and Fd=14. 8μPa−1∕2. With these outstanding pyroelectric properties, the BNKLBT ceramic can be a promising material for pyroelectric sensor applications. The BNKLBT ceramic with different thicknesses (i.e., 0.3, 0.5, and 0.7mm) have been used as the sensing element for fabricating infrared detectors. The current responsivi.
Nested subclasses of the class of $\alpha$-selfdecomposable distributions

A probability distribution $\mu$ on $\mathbb R ^d$ is selfdecomposable if its characteristic function $\widehat\mu(z), z\in\mathbb R ^d$, satisfies that for any $b>1$, there exists an infinitely divisible distribution $\rho_b$ satisfying $\widehat\mu(z) = \widehat\mu (b^{-1}z)\widehat\rho_b(z)$. This concept has been generalized to the concept of $\alpha$-selfdecomposability by many authors in the following way. Let $\alpha\in\mathbb R$. An infinitely divisible distribution $\mu$ on $\mathbb R ^d$ is $\alpha$-selfdecomposable, if for any $b>1$, there exists an infinitely divisible distribution $\rho_b$ satisfying $\widehat\mu(z) = \widehat \mu (b^{-1}z)^{b^{\alpha}}\widehat\rho_b(z)$. By denoting the class of all $\alpha$-selfdecomposable distributions on $\mathbb R ^d$ by $L^{\leftangle\alpha\rightangle}(\mathbb R ^d)$, we define in this paper a sequence of nested subclasses of $L^{\leftangle\alpha\rightangle}(\mathbb R ^d)$, and investigate several properties of them by two ways. One is by using limit theorems and the other is by using mappings of infinitely divisible distributions.
Interactions between aquatic plants and turbulent flow: a field study using stereoscopic PIV

Abstract A stereoscopic particle image velocimetry (PIV) system for use in shallow ( ${\sim }$ 0.5 m deep) rivers was developed and deployed in the Urie River, Scotland, to study the interactions between turbulent flow and a Ranunculus penicillatus plant patch in its native environment. Statistical moments of the velocity field were calculated utilizing a new method of reducing the contribution of measurement noise, based on the measurement redundancy inherent in the stereoscopic PIV method. Reynolds normal and shear stresses, their budget terms, and higher-order moments of the velocity probability distribution in the wake of the plant patch were found to be dominated by the presence of a free shear layer induced by the plant drag. Plant motion, estimated from the PIV images, was characterized by travelling waves that propagate along the plant with a velocity similar to the eddy convection velocity, suggesting a direct coupling between turbulence and the plant motion. The characteristic frequency of the plant velocity fluctuations ( ${\sim }$ 1 Hz) may suggest that the plant motion is dominated by large eddies with scale similar to the flow depth or plant length. Plant and fluid velocity fluctuations were, in contrast, found to be strongly correlated only over a narrow ( ${\sim }$ 30 mm) elevation range above the top of the plant, supporting a contribution of the shear layer turbulence to the plant motion. Many aspects of flow–aquatic plant interactions remain to be clarified, and the newly developed stereoscopic field PIV system should prove valuable in future studies.
Order computations in generic groups

We consider the problem of computing the order of an element in a generic group. The two standard algorithms, Pollard’s rho method and Shanks’ baby-steps giant-steps technique, both use Θ ( N1/2 ) group operations to compute |α| = N. A lower bound of Ω ( N1/2 ) has been conjectured. We disprove this conjecture, presenting a generic algorithm with complexity o ( N1/2 ) . The running time is O ( (N/ log logN)1/2 ) when N is prime, but for nearly half the integers N ∈ [0,M], the complexity is O ( N1/3 ) . If only a single success in a random sequence of problems is required, the running time is subexponential. We prove that a generic algorithm can compute |α| for all α ∈ S ⊆ G in near linear time plus the cost of a single order computation with N = λ(S), where λ(S) = lcm|α| over α ∈ S. For abelian groups, a random S ⊆ G of constant size suffices to compute λ(G), the exponent of the group. Having computed λ(G), we show that in most cases the structure of an abelian group G can be determined using an additional O ( Nδ/4 ) group operations, given an O ( Nδ ) bound on |G| = N. The median complexity is approximately O ( N1/3 ) for many distributions of finite abelian groups, and o ( N1/2 ) in all but an extreme set of cases. A lower bound of Ω ( N1/2 ) had been assumed, based on a similar bound for the discrete logarithm problem. We apply these results to compute the ideal class groups of imaginary quadratic number fields, a standard test case for generic algorithms. The record class group computation by a generic algorithm, for discriminant −4(1030 + 1), involved some 240 million group operations over the course of 15 days on a Sun SparcStation4. We accomplish the same task using 1/1000th the group operations, taking less than 3 seconds on a PC. Comparisons with non-generic algorithms for class group computation are also favorable in many cases. We successfully computed several class groups with discriminants containing more than 100 digits. These are believed to be the largest class groups ever computed. Thesis Supervisor: Michael F. Sipser Title: Professor of Applied Mathematics
On the stability of the rest state of fluids of complexity n

Results of Dunn & Fosdick (1974) and Fosdick & Rajagopal (1980) on the stability of ‘canister’ flows of Rivlin-Ericksen fluids of grades 2 and 3 are extended to Rivlin-Ericksen fluids of complexity n, n being any positive integer, by restricting the discussion to linear stability. The fluids of grade n form a subclass of the fluids of complexity n.
Canonical Time Variations of X-Rays from Black Hole Candidates in the Low-Intensity State

X-rays from black hole candidates, Cyg X-1, GX 339-4, and GS 2023+338 in their low-intensity state, consist of various shots or burst events, and shapes of the shots are similar among these sources. In their low-intensity states, the normalized power spectrum density functions of the X-rays except for the Fourier frequencies below about 0.2 Hz are the same not only in their shape but also in their absolute values, even if the X-ray energy range is different.
Magnetic modulation of solar luminosity by photospheric activity

The behavior of slow changes in solar irradiance S is studied using measurements obtained with radiometers on the SMM and Nimbus 7 spacecraft. The general downtrend in the radiometer readings is examined by removing the influence of sunspot blocking and comparing the residual irradiance variations with changes in facular and network radiation as indicated by the He I 10830 and CaK indices. The time-integrated sunspot and facular contributions to irradiance variation and its implications for active region energetics are considered. The magnetic activity modulation of S over solar cycle 21 from daily data on sunspot blocking and the He I index are simulated, and this simulated irradiance variation is compared to radiometry since 1978. Other recent evidence for an irradiance modulation by magnetic activity is discussed. 38 references.
Empirical Correlations for Free Convection in an Isothermal Asymmetrically Heated Vertical Channel

Laminar free convection in an isothermal asymmetrically heated vertical channel has been extensively studied in the past, and empirical correlations for the overall channel convective heat transfer rate are available in the literature. However, this problem has been revisited in order to develop empirical correlations that allow the calculation of the average Nusselt number for each channel wall separately. A numerical solution has been obtained for a Prandtl number of 0.71 and for Rayleigh numbers ranging from the conduction regime to the isolated boundary layer regime. The data have been used to develop correlations for the average Nusselt numbers on the hot and cold walls. These correlations satisfy a heat balance for the overall channel.
The Oleander Project: Monitoring the Variability of the Gulf Stream and Adjacent Waters between New Jersey and Bermuda

Abstract An overview of the first 4.5 years of operation of a program to monitor the structure and variability of the Gulf Stream (GS) is presented. A container vessel that operates on a weekly schedule between Port Elizabeth, New Jersey, and Hamilton, Bermuda, is equipped with a 150-kHz narrowband acoustic Doppler current profiler to measure currents from the surface to ∼300 m depth. A major objective of the multiyear program is to study the annual cycle and interannual variations in velocity structure and transport by the GS. In this survey the focus is on the transport and lateral structure of the current at 52-m depth. The velocity maximum is constant at 2.07 ± 0.24 m s−1 (4 kt) with a seasonal range of ∼0.1 m s−1. Seasonal and interannual variations in total transport are observed but appear to be limited to the edges of the current, apparently reflecting low-frequency variations in the intensity of the recirculating waters adjacent to the stream. The transport by the central core of the current, def.
Ion and electron irradiation-induced effects in nanostructured materials

A common misconception is that the irradiation of solids with energetic electrons and ions has exclusively detrimental effects on the properties of target materials. In addition to the well-known cases of doping of bulk semiconductors and ion beam nitriding of steels, recent experiments show that irradiation can also have beneficial effects on nanostructured systems. Electron or ion beams may serve as tools to synthesize nanoclusters and nanowires, change their morphology in a controllable manner, and tailor their mechanical, electronic, and even magnetic properties. Harnessing irradiation as a tool for modifying material properties at the nanoscale requires having the full microscopic picture of defect production and annealing in nanotargets. In this article, we review recent progress in the understanding of effects of irradiation on various zero-dimensional and one-dimensional nanoscale systems, such as semiconductor and metal nanoclusters and nanowires, nanotubes, and fullerenes. We also consider the t.
Coactions of Hopf $C^*$-algebras on Cuntz-Pimsner algebras

Unifying two notions of an action and coaction of a locally compact group on a $C^*$-cor\-re\-spond\-ence we introduce a coaction $(\sigma,\delta)$ of a Hopf $C^*$-algebra $S$ on a $C^*$-cor\-re\-spond\-ence $(X,A)$. We show that this coaction naturally induces a coaction $\zeta$ of $S$ on the associated Cuntz-Pimsner algebra $\mathcal{O}_X$ under the weak $\delta$-invariancy for the ideal $J_X$. When the Hopf $C^*$-algebra $S$ is defined by a well-behaved multiplicative unitary, we construct a $C^*$-cor\-re\-spond\-ence $(X\rtimes_\sigma\widehat{S},A\rtimes_\delta\widehat{S})$ from $(\sigma,\delta)$ and show that it has a representation on the reduced crossed product $\mathcal{O}_X\rtimes_\zeta\widehat{S}$ by the induced coaction $\zeta$. This representation is used to prove an isomorphism between the $C^*$-algebra $\mathcal{O}_X\rtimes_\zeta\widehat{S}$ and the Cuntz-Pimsner algebra $\mathcal{O}_{X\rtimes_\sigma\widehat{S}}$ under the covariance assumption which is guaranteed in particular if the ideal $J_{X\rtimes_\sigma\widehat{S}}$ of $A\rtimes_\delta\widehat{S}$ is generated by the canonical image of $J_X$ in $M(A\rtimes_\delta\widehat{S})$ or the left action on $X$ by $A$ is injective. Under this covariance assumption, our results extend the isomorphism result known for actions of amenable groups to arbitrary locally compact groups. The Cuntz-Pimsner covariance condition which was assumed for the same isomorphism result concerning group coactions is shown to be redundant.
$L^2$-index formula for proper cocompact group actions

We study the index of the $G$-invariant elliptic pseudo-differential operator acting on a complete Riemannian manifold, where a unimodular, locally compact group $G$ acts properly and cocompactly. An $L^2$-index formula was obtained using the heat kernel method.
Determining the standoff distance of the bow shock: Mach number dependence and use of models

We explore the factors that determine the bow shock standoff distance. These factors include the parameters of the solar wind, such as the magnetosonic Mach number, plasma beta, and magnetic field orientation, as well as the size and shape of the obstacle. In this report we develop a semiempirical Mach number relation for the bow shock standoff distance in order to take into account the shock's behavior at low Mach numbers. This is done by determining which properties of the shock are most important in controlling the standoff distance and using this knowledge to modify the current Mach number relation. While the present relation has proven useful at higher Mach numbers, it has lacked effectiveness at the low Mach number limit. We also analyze the bow shock dependence upon the size and shape of the obstacle, noting that it is most appropriate to compare the standoff distance of the bow shock to the radius of curvature of the obstacle, as opposed to the distance from the focus of the object to the nose. Last, we focus our attention on the use of bow shock models in determining the standoff distance. We note that the physical behavior of the shock must correctly be taken into account, specifically the behavior as a function of solar wind dynamic pressure; otherwise, erroneous results can be obtained for the bow shock standoff distance.
Defect centers in a pure‐silica‐core borosilicate‐clad optical fiber: ESR studies

An electron‐spin‐resonance (ESR) study has been carried out on γ‐ray‐induced color centers in a pure‐SiO2‐core B2O3⋅3SiO2‐clad prototype optical fiber and in bulk glasses of the core and cladding compositions. Defects in the core material included the familiar silicon E′ center and other centers tentatively attributed to oxygen‐associated structures. Approximately 102 times more centers per unit mass and unit γ‐ray dose were created in the cladding material than in the core glass; these comprised just three defect types: the boron‐oxygen hole center (BOHC), the silicon E′ center, and a boron analog of the latter, the boron E′ center. These same defects were also observed in the irradiated prototype fiber in concentrations comparable to those attained in the bulk glass of the cladding composition. The unexpectedly high radiation sensitivity of the fiber, therefore, would appear to be due to the efficient production of (intrinsic) boron‐related defects in the cladding. Considerable insight has been gained i.
Depth Estimation and Semantic Segmentation from a Single RGB Image Using a Hybrid Convolutional Neural Network

Semantic segmentation and depth estimation are two important tasks in computer vision, and many methods have been developed to tackle them. Commonly these two tasks are addressed independently, but recently the idea of merging these two problems into a sole framework has been studied under the assumption that integrating two highly correlated tasks may benefit each other to improve the estimation accuracy. In this paper, depth estimation and semantic segmentation are jointly addressed using a single RGB input image under a unified convolutional neural network. We analyze two different architectures to evaluate which features are more relevant when shared by the two tasks and which features should be kept separated to achieve a mutual improvement. Likewise, our approaches are evaluated under two different scenarios designed to review our results versus single-task and multi-task methods. Qualitative and quantitative experiments demonstrate that the performance of our methodology outperforms the state of the art on single-task approaches, while obtaining competitive results compared with other multi-task methods.
Escape from the boundary in Markov population processes

Density dependent Markov population processes in large populations of size N were shown by Kurtz (1970), (1971) to be well approximated over finite time intervals by the solution of the differential equations that describe their average drift, and to exhibit stochastic fluctuations about this deterministic solution on the scale √N that can be approximated by a diffusion process. Here, motivated by an example from evolutionary biology, we are concerned with describing how such a process leaves an absorbing boundary. Initially, one or more of the populations is of size much smaller than N, and the length of time taken until all populations have sizes comparable to N then becomes infinite as N → ∞. Under suitable assumptions, we show that in the early stages of development, up to the time when all populations have sizes at least N 1-α for 1/3 < α < 1, the process can be accurately approximated in total variation by a Markov branching process. Thereafter, it is well approximated by the deterministic solution starting from the original initial point, but with a random time delay. Analogous behaviour is also established for a Markov process approaching an equilibrium on a boundary, where one or more of the populations become extinct.