Miracle-dz/UniFAR-FTUs huggingface dataset:
Neural network adaptive robust control with application to precision motion control of linear motors

In this paper, neural networks (NNs) and adaptive robust control (ARC) design philosophy are integrated to design performance‐oriented control laws for a class of single‐input–single‐output (SISO) nth‐order non‐ linear systems. Both repeatable (or state dependent) unknown non‐linearities and non‐repeatable unknown non‐linearities such as external disturbances are considered. In addition, unknown non‐linearities can exist in the control input channel as well. All unknown but repeatable non‐linear functions are approximated by outputs of multi‐layer neural networks to achieve a better model compensation for an improved performance. All NN weights are tuned on‐line with no prior training needed. In order to avoid the possible divergence of the on‐line tuning of neural network, discontinuous projection method with fictitious bounds is used in the NN weight adjusting laws to make sure that all NN weights are tuned within a prescribed range. By doing so, even in the presence of approximation error and non‐repeatable non‐linearities such as disturbances, a controlled learning is achieved and the possible destabilizing effect of on‐line tuning of NN weights is avoided. Certain robust control terms are constructed to attenuate various model uncertainties effectively for a guaranteed output tracking transient performance and a guaranteed final tracking accuracy in general. In addition, if the unknown repeatable model uncertainties are in the functional range of the neural networks and the ideal weights fall within the prescribed range, asymptotic output tracking is also achieved to retain the perfect learning capability of neural networks in the ideal situation. The proposed neural network adaptive control (NNARC) strategy is then applied to the precision motion control of a linear motor drive system to help to realize the high‐performance potential of such a drive technology. NN is employed to compensate for the effects of the lumped unknown non‐linearities due to the position dependent friction and electro‐magnetic ripple forces. Comparative experiments verify the high‐performance nature of the proposed NNARC. With an encoder resolution of 1 µm, for a low‐speed back‐and‐forth movement, the position tracking error is kept within ±2 µm during the most execution time while the maximum tracking error during the entire run is kept within ±5.6 µm. Copyright © 2001 John Wiley & Sons, Ltd.
Convergence results for a self-dual regularization of convex problems

We study a one-parameter regularization technique for convex optimization problems whose main feature is self-duality with respect to the Legendre–Fenchel conjugation. The self-dual technique, introduced by Goebel, can be defined for both convex and saddle functions. When applied to the latter, we show that if a saddle function has at least one saddle point, then the sequence of saddle points of the regularized saddle functions converges to the saddle point of minimal norm of the original one. For convex problems with inequality and state constraints, we apply the regularization directly on the objective and constraint functions, and show that, under suitable conditions, the associated Lagrangians of the regularized problem hypo/epi-converge to the original Lagrangian, and that the associated value functions also epi-converge to the original one. Finally, we find explicit conditions ensuring that the regularized sequence satisfies Slater's condition.
Length scales in wall-bounded high-Reynolds-number turbulence

In this study, estimates of inhomogeneous integral scales are derived from rapid distortion theory (RDT) for the case of wall-bounded high-Reynolds-number turbulence and from large-eddy simulation (LES) of a neutrally stratified atmospheric boundary layer (ABL). As for any inhomogeneous flow, integral scales in different directions are introduced. Downward integral scales are introduced since they differ from the usual vertical integral scales because of the presence of the wall. The study concentrates on the length scales based on the vertical velocity, which are the most affected by blocking by the wall, which is assumed to be horizontal. It is shown from RDT that the asymptotic behaviour of the integral length scales for small heights depends crucially on the spectrum power law $-2p$. When $2p>1$ there is always one length scale which does not scale with the distance to the wall $z$. Only the downward integral scale is proportional to $z$ for any $2p$. These results show that the assumption, often made in studies of boundary layers, that all the lengths are proportional to $z$, is not compatible with the assumption of a spectrum decaying according to Kolmogorov's law, but rather with a spectrum following a $-1$ power law. It is an encouraging result since there is now widespread theoretical, experimental and numerical evidence that such a $-1$ power-law subrange exists in the spectra of high-Reynolds-number wall-bounded turbulence, for eddies larger than $z$. The RDT results allow an interpretation of the vertical profiles of the integral length scales computed from the LES outputs: above the third grid point, the vertical profiles of the integral length scales have a linear shape, as expected for high-Reynolds-number turbulence and $2p=1$. Very close to the surface, the upward integral length scales decreases with $z$ because of the fast decay of the spectrum ($2p>2$) from the LES subgrid model. The longitudinal-to-transverse integral length scale ratio is computed using RDT and LES. This ratio is interpreted as the aspect ratio of elongated near-wall large eddies, which are ubiquitous features of LES of boundary layers in which shear plays an important role in the dynamics. The LES shows that the longitudinal-to-transverse integral length scale ratio is an increasing function of $z$, ranging between 1 and 3, which is of the order of magnitude of the published theoretical value of 3.5. From RDT, the evolution with $z$ of the longitudinal-to-transverse integral length scale ratio means either that the velocity shear $\beta$ decreases with $z$ and the spectral power law $2p$ varies in a non-trivial manner, or if both the RDT and LES are valid that the scale of the large eddies is proportional to $\beta z$ with $\beta$ varying from 1.3 to about 4.
High Spatial Resolution Imaging of Pre-Main-Sequence Binary Stars: Resolving the Relationship between Disks and Close Companions

In order to study the passive and active effects of young close companion stars and to constrain possible multiple star formation mechanisms, we have carried out a high-resolution imaging program of six multiple T Tauri star systems using the Hubble Space Telescope from 0.3 to 0.9 μm and ground-based speckle imaging from 1 to 2 μm. Each system (GG Tau, UZ Tau, DF Tau, RW Aur, V773 Tau, and V410 Tau) has at least one binary pair with separation between 0. ″07 and 0. ″4 (10-50 AU). In addition to the previously known companions, a third component is discovered in the V410 Tau system. Many of the companion stars contribute significantly to the unresolved spectral energy distribution and thereby bias the inferred stellar and circumstellar properties. Age is the most systematically biased quantity; neglecting a companion causes an overestimate in age by a factor of ~2 typically and more than 10 in the extreme. Excess emission above the photospheric level is detected at ultraviolet (UV) and near-infrared (NIR) wavelengths for several of the components, which suggests that some close (10-50 AU) T Tauri binaries support at least a minimal circumstellar disk at an age of ~1 Myr. These inner disks not only provide a potential reservoir of material for planetary formation but also may play a key role in the evolution of the components' angular momenta. Possible multiple star formation scenarios are explored in light of the components' relative stellar and circumstellar properties for systems studied here as well as wider and closer systems whose properties are reported in the literature. In summary, the components (1) are coeval, (2) have secondary mass and mass ratio distributions that appear to be independent of both the primary stars' mass and the binary separation, and (3) have UV and NIR excess emission that is either similar or more dominant in the primary. These properties support a scenario in which binary stars form via core fragmentation.
Logarithmic convexity and the “slow evolution” constraint in ill-posed initial value problems

This paper examines a wide class of ill-posed initial value problems for partial differential equations, and surveys logarithmic convexity results leading to Holder-continuous dependence on data for solutions satisfying prescribed bounds. The discussion includes analytic continuation in the unit disc, time-reversed parabolic equations in L p spaces, the time-reversed Navier--Stokes equations, as well as a large class of nonlocal evolution equations that can be obtained by randomizing the time variable in abstract Cauchy problems. It is shown that in many cases, the resulting Holder-continuity is too weak to permit useful continuation from imperfect data. However, considerable reduction in the growth of errors occurs, and continuation becomes feasible, for solutions satisfying the slow evolution from the continuation boundary constraint, previously introduced by the author.
Rotating channel flow: Control and upstream currents

Abstract Theory and experiments are presented for critically controlled flow of a layer of inviscid rotating fluid. Flow is controlled by a level passage. For a wide upstream channel of fixed depth (i.e. constant potential vorticity) the volume flux on the right-hand wall is unaffected by passage flow. This suggests that specifying Bernoulli potential on the right-hand passage wall produces a physically well-posed condition. The specification results in one less dimensionless number than was required by previous formulations to specify flow in the controlled passage. The upstream flow needs the same number as before, so that a range of upstream conditions produce exactly the same passage flow. A laboratory study is conducted using a thin layer of water under air. This is pumped in steadily at various locations in a deep rotating upstream basin, with fluid leaving through a level passage. All currents in the upstream basin cross to the left-hand wall as the current approaches the passage over a sloping bottom. The current crosses back to the right-hand wall within the passage. Velocity profiles of currents agree reasonably well with constant potential vorticity theory. To the right of the detached upstream current is a closed gyre that connects the upstream flows (that have different patterns depending on source location) with the unique passage flows. The results suggest that gyres upstream of critically controlling passages in the ocean might serve as adjustment regions between the relatively unconstrained upstream flows and the tightly controlled passage flows.
Cool White Dwarfs in Cataclysmic Variables: Hubble Space Telescope Results on EG Cancri and HV Virginis

Our Hubble Space Telescope (HST) ultraviolet spectra of the low mass transfer rate cataclysmic variables EG Cnc and HV Vir at 4 yr and 8 yr past their last superoutburst have shown that the white dwarfs in these systems are among the coolest yet observed in disk-accreting close binaries. The UV-optical fluxes of EG Cnc are consistent with a 11,700-13,000 K white dwarf at a distance of 350-475 pc, while those of HV Vir fit with a 12,500-14,000 K white dwarf at 400-550 pc, with log g = 8.0 ± 0.5 for both stars. In each case, the metal abundance is near 0.3 solar, while the rotation rates are considerably less than breakup. If these systems formed above the period gap and evolved to their short periods in an evolution time of several Gyr, then their white dwarfs are hotter than field white dwarfs of comparable age and hotter than those in close binary systems of similar orbital period that contain magnetic white dwarfs. If these systems have indeed passed the period minimum in their evolution, the implication is that they are significantly heated by the long-term effects of mass transfer from their close companions.
Boundedness of bilinear pseudo-differential operators of S 0 , 0 -type on L 2 × L 2

Weextendtheknownresultthatthebilinearpseudo-differentialoperatorswithsymbols in the bilinear Hörmander class BS − n / 2 0 , 0 ( R n ) are bounded from L 2 × L 2 to h 1 . We show that those operators are also bounded from L 2 × L 2 to L r for every 1 < r ≤ 2. Moreover we give similar results for symbol classes wider than BS − n / 2 0 , 0 ( R n ) . We also give results for symbols of limited smoothness
Statistical analysis of bidirectional reflectance distribution functions

Bidirectional Reflectance Distribution Functions (BRDFs) are commonly employed in Computer Graphics and Computer Vision to model opaque materials. On the one hand, a BRDF is a complex 4D function of both light and view directions, which should ensure reciprocity and energy conservation laws. On the other hand, when computing radiance reaching the eye from a surface point, the view direction is held fixed. In this respect, we are only interested in a 2D BRDF slice that acts as a filter on the local environment lighting. The goal of our work is to understand the statistical properties of such a filter as a function of viewing elevation. To this end, we have conducted a study of measured BRDFs where we have computed statistical moments for each viewing angle. We show that some moments are correlated together across dimensions and orders, while some others are close to zero and may safely be discarded. Our study opens the way to novel applications such as moment-based manipulation of measured BRDFs, material estimation and image-based material editing. It also puts empirical and physically-based material models in a new perspective, by revealing their effect as view-dependent filters.
Active boundary-layer control in diffusers

Flow separation in diffusers leads to loss in energy recovery and is often a source of unsteadiness due to stall movements. We investigate the use of wall jets as a remedy to these problems. New jet geometries are compared to the conventional annular blowing. Steady wall jets are found to be capable of raising the mean pressure recovery in both conical and rectangular air diffusers, but high injected mass flow rates are required before the flow in rectangular diffusers becomes steady. Active feedback control is applied to reduce this flow unsteadiness. To implement the control, the air supplied through the wall jets is modulated in response to the unsteady pressures within the diffuser. Results are presented for two feedback mechanisms.
Evidence for charge-density-wave nature of the charge-ordered phase in La 1/3 Sr 2/3 FeO 3

Javier Herrero-Martin,1 Gloria Subias,2 Joaquin Garcia,2,* Javier Blasco,2 and M. Concepcion Sanchez2 1European Synchrotron Radiation Facility, BP 220, 38043 Grenoble Cedex 9, France 2Departamento de Fisica de la Materia Condensada, Instituto de Ciencia de Materiales de Aragon, CSIC-Universidad de Zaragoza, Pedro Cerbuna 12, 50009 Zaragoza, Spain Received 24 June 2008; revised manuscript received 22 October 2008; published 27 January 2009
Characterizations of pseudo-differential operators on S 1 based on Separation-Preserving operators

In this paper we prove that a bounded pseudo-differential operator T σ : L p ( S 1 ) → L p ( S 1 ) for 1 ≤ p < ∞ , is a Separation-Preserving operator and give a formula for its symbols σ . Using these formulas we give a new representation for the symbol of adjoint and products of two pseudo-differential operators
Enhanced field emission properties of thin-multiwalled carbon nanotubes: Role of SiOx coating

We report the fabrication, characterization, and field emission properties of (silicon oxide) SiOx coated thin-multiwalled carbon nanotubes (t-MWNTs). The coated t-MWNTs show improved field emission behavior. Initially, raw t-MWNTs (diameter ∼5–8nm) were functionalized by acid treatment. Using spin on glass as a Si precursor, SiOx was coated on the nanotubes by routine chemical methods. The coated samples were characterized by high resolution transmission electron microscopy (HRTEM), Fourier transform infrared (FTIR) spectroscopy, and thermogravimetric analysis (TGA) techniques. The HRTEM results show that the local thickness of the coating varies from ∼1to2nm. The FTIR investigations show the formation of nanophases, such as Si–C, Si–O–C, and intercalated Si–O, at the coating/nanotube interface. The TGA reveals that the coating prevents the high-temperature oxidation and degradation of the nanotubes. The field emission characteristics of the coated, functionalized, and raw nanotubes show that the turn-on.
High Temperature RF Characterisation of SiN Passivated and Unpassivated AlGaN/GaN HFETs

AlGaN/GaN heterojunction field effect transistors were tested at elevated temperatures, up to +180°C, to determine the effect on the device performance. Ageing of the device during these measurements was also studied. A comparison between devices fabricated with and without silicon nitride surface passivation was made. For devices with surface passivation, both f T and f max reduce with increasing temperature. This is different from the behaviour of the devices without surface passivation. In these devices, there is an initial increase in both f T and f max . Above 70°C, any further increase in temperature causes a reduction in both f T and f max . When devices are allowed to cool to room temperature and are subsequently re-measured, they show an increase in f T and f max from the values initially recorded; thus indicating some form of device anneal.
Scaling of heat transport with beta in the DIII-D tokamak

Experiments in the DIII-D tokamak have measured the scaling of heat transport with beta (β) while all other dimensionless parameters are held constant for both H mode and L mode plasmas. Experimental results from the beta scaling of heat transport help to differentiate between various proposed mechanisms of turbulent transport. For L mode plasmas, the beta scaling of heat transport over the range 0.26 ≤ βN ≤ 0.49 is close to zero, with the thermal confinement time scaling as Bτth ∝ β-0.05±0.10 and the effective (or one fluid) thermal diffusivity scaling as χeff ∝ χBβ0.11±0.20. The beta scalings of the ion and electron thermal diffusivities are the same as the effective diffusivity to within the experimental errors. Higher values of beta are investigated in H mode plasmas, where a weak-to-moderate beta scaling of transport is observed over the range 0.8 ≤ βN ≤ 1.7, with the thermal confinement time scaling as Bτth ∝ β0. 03±0.11 and the effective thermal diffusivity scaling as χeff ∝ χBβ-0.54±0.21. The ion channel is responsible for the favourable beta scaling of H mode plasmas; the electron channel has no measurable beta dependence. These beta scalings determined by dimensionless parameter scans are much weaker than the predicted beta scalings from the L mode and H mode confinement scaling expressions that are currently being used to predict the performance of ITER.
Nemytskii operator on ( (cid:2) , 2 , ˛ ) -bounded variation space in the sense of Riesz

In this paper we show that if the Nemytskii operator maps the (φ, 2 , α) -bounded variation space into itself and satisﬁes some Lipschitz condition, then there are two functions g and h belonging to the (φ, 2 , α) -bounded variation space such that f ( t , y ) = g ( t ) y + h ( t ) for all t ∈ [ a , b ] , y ∈ R .
Intense, mixed-energy hydrogen beams for CTR injection

Present high-current ion sources for neutral injection experiments accelerate a mixture of atomic and molecular hydrogen species that are converted into neutral particles with different energies and neutralization efficiencies. Beam composition can have important effects on injection system efficiency, vacuum design, and first-wall loading. Beam composition measurements of the 20-keV LBL high-current sources are used to calculate the relative power in the various hydrogen and deuterium beam components expected at higher energies.
Alternative epidemic indicators for COVID-19: a model-based assessment of COVID-19 mortality ascertainment in three settings with incomplete death registration systems

Not all COVID-19 deaths are officially reported and, particularly in low-income and humanitarian settings the magnitude of such reporting gaps remain sparsely characterised. Alternative data sources, including burial site worker reports, satellite imagery of cemeteries and social-media-conducted surveys of infection, may offer solutions. By merging these data with independently conducted, representative serological studies within a mathematical modelling framework, we aim to better understand the range of under-reporting using the example of three major cities: Addis Ababa (Ethiopia), Aden (Yemen) and Khartoum (Sudan) during 2020. We estimate 69% - 100%, 0.8% - 8.0% and 3.0% - 6.0% of COVID-19 deaths were reported in these three settings, respectively. In future epidemics, and in settings where vital registrations systems are absent or limited, using multiple alternative data sources could provide critically-needed, improved estimates of epidemic impact. However, ultimately, functioning vital registration systems are needed to ensure that, in contrast to COVID-19, the impact of future pandemics or other drivers of mortality are reported and understood worldwide.
Risk factors for long COVID among healthcare workers, Brazil, 2020

Objectives: We aimed to determine risk factors for the development of long coronavirus disease (COVID) in healthcare workers (HCWs). Methods: We conducted a case-control study among HCWs who had confirmed COVID-19 infection working in a Brazilian healthcare system between March 1, 2020 and July 15, 2022. Cases were defined as those having long COVID per the Centers for Disease Control and Prevention definition. Controls were defined as HCWs who had documented COVID-19 infection but did not develop long COVID. Multiple logistic regression was used to assess the association between exposure variables and long COVID during 180 days of follow-up. Results: Of 7,051 HCWs diagnosed with COVID-19 infection, 1,933 (27.4%) who developed long COVID were compared to 5,118 (72.6%) who did not. The majority of those with long COVID (51.8%) had 3 or more symptoms. Factors associated with development of long COVID were female sex (OR 1.21 [CI95 1.05-1.39]), age (OR 1.01 [CI95 1.00-1.02]), and two or more COVID-19 infections (1.27 [CI95 1.07-1.50]). Those infected with the Delta variant (OR 0.30 [CI95 0.17-0.50]) or the Omicron variant (OR 0.49 [CI95 0.30-0.78]), and those receiving four COVID-19 vaccine doses prior to infection (OR 0.05 [CI95 0.01-0.19]) were significantly less likely to develop long COVID. Conclusions: Long COVID can be prevalent among HCWs. We found that acquiring more than one COVID-19 infection was a major risk factor for long COVID, while maintenance of immunity via vaccination was highly protective.
Some Remarks on Left‐Definite Hamiltonian Systems in the Regular Case

It is the aim to confront recent considerations of A.M. Krall on the left‐definite spectral theory of regular Hamiltonian systems with the results of former research in this field. A short survey of the main sources starting with the work of E. Hölder in 1935 is given. After that the essential features of the left‐definite S‐hermitian theory, as it was developed by Schäfke and Schneider in 1965, are presented for the special case of the problems treated by Krall, and an application to Sturm ‐ Liouville equations is given. By comparing methods and assumptions of both theories, it is shown that the main result in Krall's papers, a theorem on eigenfunction expansions, can be obtained under much weaker conditions. Especially one gets rid of the problem that the restrictions in the work of Krall even exclude the classical polar case which builds the starting‐point of the left‐definite theory.