Miracle-dz/UniFAR-FTUs huggingface dataset:
Stabilization of a swept-wing boundary layer by distributed roughness elements

Abstract The stabilization of a swept-wing boundary layer by distributed surface roughness elements is studied by performing direct numerical simulations. The configuration resembles experiments studied by Saric and coworkers at Arizona State University, who employed this control method in order to delay transition. An array of cylindrical roughness elements are placed near the leading edge to excite subcritical cross-flow modes. Subcritical refers to the modes that are not critical with respect to transition. Their amplification to nonlinear amplitudes modifies the base flow such that the most unstable cross-flow mode and secondary instabilities are damped, resulting in downstream shift of the transition location. The experiments by Saric and coworkers were performed at low levels of free stream turbulence, and the boundary layer was therefore dominated by stationary cross-flow disturbances. Here, we consider a more complex disturbance field, which comprises both steady and unsteady instabilities of similar amplitudes. It is demonstrated that the control is robust with respect to complex disturbance fields as transition is shifted from 45 to 65 % chord.
Kinetic theory representation of hydrodynamics: a way beyond the Navier–Stokes equation

We present in detail a theoretical framework for representing hydrodynamic systems through a systematic discretization of the Boltzmann kinetic equation. The work is an extension of a previously proposed formulation. Conventional lattice Boltzmann models can be shown to be directly derivable from this systematic approach. Furthermore, we provide here a clear and rigorous procedure for obtaining higher-order approximations to the continuum Boltzmann equation. The resulting macroscopic moment equations at each level of the systematic discretization give rise to the Navier–Stokes hydrodynamics and those beyond. In addition, theoretical indications to the order of accuracy requirements are given for each discrete approximation, for thermohydrodynamic systems, and for fluid systems involving long-range interactions. All these are important for complex and micro-scale flows and are missing in the conventional Navier–Stokes order descriptions. The resulting discrete Boltzmann models are based on a kinetic representation of the fluid dynamics, hence the drawbacks in conventional higher-order hydrodynamic formulations can be avoided.
Change Points in High Dimensional Settings

While there is considerable work on change point analysis in univariate time series, more and more data being collected comes from high dimensional multivariate settings. This paper investigates change point detection procedures using projections and develops asymptotic theory for how full panel (multivariate) tests compare with both oracle and random projections. This is done by considering an analogous concept to asymptotic relative efficiency termed high dimensional efficiency. This provides the rate at which the change can get smaller with dimension while still being detectable. The effect of misspecification of the covariance on the power of the tests is investigated, because in many high dimensional situations estimation of the full dependency (covariance) between the multivariate observations in the panel is often either computationally or even theoretically infeasible. It is shown that if information concerning the direction of change is available, then projecting in this direction is always advantageous over the use of a panel statistic, in terms of size and power, particularly when the covariance is misspecified. Even if the change is not known, the projection method achieves a better power as long as the difference between the true change and the direction of the projection is small. The features of the tests are quantified in theory and simulations indicate that these results are indicative of small sample behaviour.
Conformal mappings involving curvilinear quadrangles

The conformal mapping of a curvilinear quadrangle to a half-plane is a classical problem in analysis; it occurs during the analytical solution of free-boundary problems involving groundwater flows. Apart from degenerate cases, in general, it is not known how to perform such mappings; the difficulty arises because the mapping functions are given by the solutions of a Fuchsian differential equation. For a quadrangle this Fuchsian equation involves both accessory parameters and free points that are unknown a priori; the analysis of such equations is therefore difficult, and there are usually no obvious solutions. In this paper conformal mappings involving a special class of curvilinear quadrangles are constructed, and a general approach is devised in the special cases when one (or more) vertex angle is equal to 2π. By implication this suggests that there are degenerate classes of Fuchsian equations involving accessory parameters and free points; these classes are discussed.
Analysis and design of L-probe proximity fed-patch antennas

In this paper, the finite-difference time-domain (FDTD) method is employed to analyze L-probe proximity-fed rectangular patch antennas. Numerical results for the input impedance, co- and cross-polarization radiation patterns are presented and compared with the measurements. Good agreement between the computed and measured results is obtained. The effects of geometric parameters on the characteristics of the L-probe patch antenna are extensively studied. For design purposes, the variation of input impedance at resonance with different geometric parameters is plotted on a Smith chart. Mutual coupling between two L-probe patch antennas is also investigated.
Modeling of Spectralon diffusers for radiometric calibration in remote sensing

Onboard calibration of radiometric measurements in remote sensing is often achieved by observation of a sun-illuminated reflectance secondary standard using previously calibrated reflecting diffusers. In the calibration procedure, information such as the bidirectional reflectance distribution function (BRDF) of the diffuser outside the measured calibration set, or a model of the degradation of the diffuser performance in space conditions, is required. We have modeled the measured BRDF calibration data of the Spectralon ® diffusers used in the Medium Resolution Imaging Spectrometer (MERIS) currently operated as part of the Earth-observing satellite ENVISAT. The diffuser is modeled by a layered structure where the light transport in the layers is described by radiative transfer theory. The BRDF is characterized by a limited number of parameters describing the optical properties of the material, e.g., albedo, optical thickness, and anisotropy of the scattering. We also describe the result of modeling the degradation of a Spectralon diffuser after deposition, under UV radiation, of a silicone layer.
Information tools for sustainable development : Enabling distributed human intelligence

In the field of sustainable development, numerous information tools, many of them connected through computer networks, support users in their individual activities. However, these tools cannot always be effectively used, as problems occur with the quality and accessibility of the data on which they operate. Another major issue is that these tools are not very well suited to support collaborative problem solving. One solution proposed by some is distributed artificial intelligence. We argue that in many cases groupware provides a more viable approach as it enables strong collaboration between human stakeholders. To optimally support professional communities, network information systems must be constructed. Such systems consist of suites of information tools supporting both individual and group needs. The users themselves must be actively involved in their incremental design. Specification methods must be available to this purpose.
Global stabilization of partially linear composite systems using homogeneous method

A linear feedback control scheme to globally stabilize a class of partially linear composite systems is proposed from the point view of homogeneity. Assume that the global stability of the zero dynamics of the nonlinear subsystem can be tested by using a homogeneous Lyapunov function. It is shown that the stabilization of the linear controllable subsystem from its own states equals to the stabilization of the whole systems if the nonlinearities satisfy a homogeneous inequality condition. Then we assume that the states are not measurable and also extend the method developed for state‐feedback control to the output‐feedback case.
Design of encircling remote field eddy-current probe

This paper explains the progress in designing a shielded encircling remote-field eddy-current (RFEC) probe to inspect nuclear fuel rods and investigates resulting signal characteristics. To force electromagnetic energy from the encircling exciter coil to penetrate into the rod, the exciter coil is shielded outside. The effects of the shielding and operating frequency are studied by finite-element analysis and the location for the sensor coil is decided. The sensor coil is also shielded to prevent direct influence from exciter fields. The totally shielded probe dramatically improves signal characteristics. Numerical modeling with the designed probe shows that the phase signal is almost equally sensitive to inner- and outer-diameter defects and there is a linear relationship between phase signal strength and defect depth, which are typical characteristics of RFEC signal.
Phrasal signatures in articulation

As research in speech production becomes more integrated with linguistic theory, it has become increasingly clear that segmental articulation can not be understood independently of prosodic structure. We see evidence for prosodic structure in the physical act of articulation—that is, not just in what we say but in how we say it. These phonological influences pervade low-level articulatory behavior. Despite the pervasiveness of these effects, only a very few articulatory correlates of prosodic structure—what we call “prosodic signatures”—have been identified.
Localization in Microresonator Arrays: Influence of Natural Frequency Tuning

Intrinsic localized modes are localization events caused by intrinsic nonlinearities within an array of perfectly periodic coupled oscillators. Recent developments in microscale fabrication techniques have allowed for the studies of this phenomenon in micro-electromechanical systems. Studies have also identified a relationship between the spatial profiles of intrinsic localized modes and forced nonlinear vibration modes, as well as a potential sensitivity to fundamental frequency relationships of one-to-one and three-to-one between adjacent oscillators. For the system considered, the one-to-one frequency relationship is determined to provide nonideal conditions for studying intrinsic localized modes. The influence of the three-to-one frequency relationship on the behavior of the intrinsic localized modes is studied with analytical methods and numerical simulations by tuning the fundamental frequencies of the oscillators. While the perfect tuning condition is not determined to produce a unique phenomenon, the number and energy concentration of the localization events are found to increase with the increased frequency ratio, which results in a decrease in the effective coupling stiffness within the array.
Some new correlation measurements in a turbulent boundary layer

This paper presents some new velocity correlation measurements in a two-dimensional zero-pressure-gradient turbulent boundary layer; these extend the work of Grant (1958). The most detailed of the new measurements concern: correlations between velocity fluctuations in the mean flow direction and fluctuations perpendicular to the wall at a different point, usually but not always in the same plane parallel to the wall; correlations between velocity fluctuations in the mean flow direction and fluctuations perpendicular to this but parallel to the wall, usually but not always close to the wall with the separation in the same direction as the latter velocity fluctuation; and various correlations with a fixed separation normal to the wall and a simultaneous variable separation in the mean flow direction. The results are not consistent with any of the various models of the large eddy structure that have been proposed. The features of the present work most relevant to the formulation of a substitute are brought together in §9. Included are suggestions that the similarities between the wall and outer regions are more marked than the differences, and that the description of the large eddies in the wall region as a coherent eruption from the viscous sublayer is unsatisfactory. The new experiments are considered in connexion with three questions posed by the previous work. These concern the large eddy contribution to the Reynolds stress; the asymmetry between upstream and downstream separations when there is also a separation normal to the wall; and the similarity between boundary layers and channel flow. A complicated situation surrounds the first point; there are arguments suggesting that the large eddy contribution might in some places be of opposite sign to the total Reynolds stress, but this no longer seems so likely. The upstream-downstream asymmetry is also more complicated than had been previously supposed, but the results can be systematically interpreted if the peaks of the correlation curves are considered in connexion with continuity and the tails of the curves are considered in connexion with the shearing action of the mean flow. Regarding the third point, the present experiments give no indication of any difference in the large eddy structure in the wall regions of boundary layer turbulence and channel flow turbulence. Section 5 gives a brief account of some experiments with a vibrating ribbon in the turbulent boundary layer.
Mass Generation in Structural Algebraic Quantum Field Theory: An alternative to the Higgs mechanism

Within the recently proposed structure-inclusive algebraic formulation of quantum field theory, we show that a massless particle can acquire mass by special nonlinear coupling to a universal massless scalar field; establishing an alternative to the Higgs mechanism in the standard model of particle physics. We end with a conjecture concerning dark energy and dark matter.
Second-order approximation to the 3DVAR cost function: application to analysis/forecast

The analysis/forecast cycling scheme used in operational weather prediction centers involves repeated application of a 3DVAR assimilation phase followed by a forecast phase. In this paper we first derive a closed-form expression for the complete Hessian of the 3DVAR objective function. This facilitates the use of Newton-like algorithms in the 3DVAR assimilation phase. It is also shown that this algorithm includes the standard first-order method as a special case. Notwithstanding the method used in this optimization phase, if the iterative optimization is terminated prematurely before convergence (generally for the sake of economy), the resulting analysis incurs an error that will corrupt the initial condition of the model and thereby affect the forecast. Using Lorenz’s maximum simplification form of the barotropic vorticity equation, we examine the assimilation error and its dependency on the following factors: observational and background error covariances and the optimization strategy.
Defective state analysis in silicon carbide

Native or process-induced defective states may significantly affect the transport properties of silicon carbide. It is then of fundamental importance to detect them and, possibly, to identify their origin. This paper deals with the defect analysis of silicon carbide using capacitance transient spectroscopy. Electrical characterization can evaluate transport mechanisms and diode quality. Deep levels found can be ascribed to impurities introduced during growth and metallization.
The Hipparcos distances of open clusters and their implication on the local variations of the ΔY/ΔZ ratio

Arguments are collected to demonstrate that recent Hipparcos results on the distances of open clusters are in agreement with previous estimates in the Russian literature which have pointed to a shorter distance scale. Evidence of the absence of a universal correaltion between Helium and metal abundances is given. It is suggested that violations of this correlation may explain the apparent contradictions between the relative positions of the main sequences of open clusters found from the Hipparcos distances.
Repetitive Learning Control Design and Period Uncertainties

The aim of this brief is to show how stability proofs in the time‐domain involving suitable quadratic‐integral Lyapunov‐like functions can be derived in the repetitive control design scenario in the case of uncertain period for the reference signals/disturbances to be tracked/rejected. Even though the presented arguments are rather general, we apply them to the generalization of the proportional–integral–derivative (PID)‐like learning control that has been recently designed. The use of the presented results in multi‐link robot synchronization tasks provides simple and intuitive solutions to as yet unsolved problems.
SUPERHUMPS IN CATACLYSMIC BINARIES. III. V795 HERCULIS

We report photometry of the cataclysmic variabla V795 Herculis during 1990-94. Comparison of recent with previously published data shows that the 2.78 hr periodicity has essentially disappeared; the amplitude has diminished by a factor of at least 10. In its place, there is a low-amplitude signal near the radial-velocity (orbital? ) period of 2.60 hr. During 1983-89, the star did show an obvious 2.78 hr signal. We study the published data on this signal, together with our own data under the (questionable) assumption that the signal still exists with an amplitude too small to survive the rigors of unbiased period detection. The data are really too sparse and too poorly distributed to decide the issue of phase stability. But since the photometric signal is transient and exceeds the likely orbital period by ~8%, the photometric waves are likely to be yet another example of "superhumps," the phenomenon made famous by dwarf novae in superoutburst. At high frequencies, the star shows a quasi-periodic signal with P ~1160 s, and possibly also a stable signal with P = 1310.2 s (or 1330.4 s, the one-day alias). The beat period between these signals could be the orbital period, or that of the vanished superhump.
A POISSON FORMULA FOR SEMI-SIMPLE LIE GROUPS*

for some bounded function h on the boundary of the disc. The function h(z) determines a function h(g) on G by setting h(g) = h(g(O)). If h(z) is harmonic, it may be shown that h(g) is annihilated by a certain class of differential operators on G. The Poisson formula (1) may be used to express h(g), and we find that here it takes on a particularly simple form. Namely, if we denote by m the normalized Lebesgue measure on {j z I = 1}, and by gm, the transform of this measure by the group element g E G, then it can be seen that (1) becomes
A novel two-step laser crystallization technique for low-temperature poly-Si TFTs

We present investigations on a novel technique for preparing low-temperature poly-Si thin-film on glass substrates using two-step laser crystallization. In the first step, seeds are created by excimer laser induced crystallization of very thin (26 nm) amorphous silicon (a-Si) thin-films deposited by plasma enhanced chemical vapor deposition (PECVD). A second (a-Si) thin-film of 80-120 nm is used to obtain large crystalline grains grown around the seed crystallites during the second laser crystallization. Using this two-step crystallization (TSC) approach, we fabricated poly-Si thin-film transistors (TFTs) with electron mobility of 103 cm/sup 2//V/spl middot/s and ON/OFF current ratio of 10/sup 7/. They are two times and four times higher than those of the poly-Si TFTs fabricated in the same run using conventional single-step excimer laser crystallization.
Statistical Analysis of Cell Motion

Statistical Analysis of Cell Motion by Edward Luke Ionides Doctor of Philosophy in Statistics University of California, Berkeley Professor David R. Brillinger, Chair Certain biological experiments investigating cell motion result in time lapse video microscopy data which may be modeled using stochastic differential equations. These models suggest statistics for quantifying experimental results and testing relevant hypotheses, and carry implications for the qualitative behavior of cells and for underlying biophysical mechanisms. A state space model formulation is used to link models proposed for cell velocity to observed data. Sequential Monte Carlo methods enable parameter estimation and model assessment for a range of applicable models. One particular experimental situation, involving the effect of an electric field on cell behavior, is considered in detail. There are several reasons why one might carry out parameter estimation by maximizing a smooth approximation to the likelihood in preference to the widely used method of maximum likelihood. If the likelihood is approximated by Monte Carlo simulation then a smoothed approximation may be all that can reasonably be obtained. If the likelihood function has many local maxima then a smooth approximation can lead to a more tractable and possibly more appropriate maximization problem. A theory for maximum smoothed likelihood estimation is developed using the framework of local asymptotic normality (LAN). This property of LAN is demonstrated for certain state space models whose state process is a diffusion process.
Limitations of Decentralized Control

The limitations of decentralized control laws are investigated. Necessary conditions for the existence of a decentralized control law that achieves particular feedback system requirements are developed. If these conditions are violated, no decentralized control law can achieve the specie ed system requirements. The necessary conditions involve only properties of the plant and performance specie cations. They are not functions of the control law and can be examined prior to control law synthesis. By evaluating the necessary conditions, it is shown that decentralized control may be unable to achieve a specie ed complementary sensitivity if large separation of subsystem bandwidths is required. It is also shown that if the system possesses certain distinctive pole/zero locations, then no decentralized control law can stabilize the system. These properties are interpreted in terms of special uncontrollability/unobservability characteristics between the subsystems. Nomenclature j = . i1/ 1=2 K.s/; G.s/ = compensator, plant transfer function matrices S.s/; T.s/ = sensitivity, complementary sensitivity matrices s = Laplace transform variable u.s/;y.s/ = vectors of plant controls, responses UB; LB = upper bound, lower bound ! = frequency
A NEW LOCAL AND PARALLEL FINITE ELEMENT ALGORITHM BASED ON THE PARTITION OF UNITY

Derived from a combination of the two-grid method and the partition of unity based domain decomposition method, a new local and parallel ﬁnite element algorithm is provided for the elliptic boundary value problem in this paper. The notable features of the present method are three-fold: (1)the ﬂexibility and controllability of domain decomposition based on partition of unity; (2)the step of global ﬁne grid correction is replaced by solving a series of locally deﬁned approximate residual problems with homogeneous Dirichlet boundary conditions on some ﬁner grids; (3)a global continuous ﬁnite element solution is constructed by solving a coarse grid correction problem and assembling all the local solutions together using the partition of unity subordinate. Some optimal error estimates in L 2 and energy norms are proved under some approximate assumptions and using new analysis results. Also, several numerical simulations are presented to demonstrate the high eﬃciency and ﬂexility of the new algorithm.