Miracle-dz/UniFAR-FTUs huggingface dataset:
Spectral interferometry-based dispersion characterization of microstructured and specialty optical fibers using a supercontinuum source

Two spectral interferometric techniques employing a supercontinuum source are used for dispersion characterization of birefringent microstructured and specialty optical fibers over a broad spectral range (e.g. 500-1600 nm). First, a technique employing an unbalanced Mach-Zehnder interferometer is used for measuring the chromatic dispersion and zero-dispersion wavelength of one polarization mode supported by a microstructured optical fiber. Second, a technique employing a tandem configuration of a Michelson interferometer and a fiber under test is used for measuring the group modal birefringence dispersion of the fiber and the chromatic-dispersion difference as a function of wavelength. From these measurements, the chromatic dispersion and the zero-dispersion wavelength of the other polarization mode supported by the microstructured optical fiber are retrieved. We revealed from four measurements the dependence of the zero-dispersion wavelength on the geometry of air-silica microstructured optical fiber. We also measured by the second technique the zero-chromatic-dispersion difference wavelength for elliptical-core optical fibers. We revealed from four measurements that the dispersion parameter can be tuned by the fiber geometry.
Time-resolved diffuse optical spectroscopy of small tissue samples

Time-resolved transmittance measurements were performed in the wavelength range of 610 or 700 to 1050 nm on phantom slabs and bone tissue cubes of different sizes. The data were best fitted with solutions of the diffusion equation for an infinite slab and for a parallelepiped to investigate how size and optical properties of the samples affect the results obtained with the two models. When small samples are considered, the slab model overestimates both optical coefficients, especially the absorption. The parallelepiped model largely compensates for the small sample size and performs much better also when the absorption spectra are interpreted with the Beer's law to estimate bone tissue composition.
Effect of flow profile on low frequency drift-type waves in a dusty plasma

A nonlocal theory has been developed to study the effect of a flow profile on the stability of low frequency drift-type instability in an inhomogeneous, dusty plasma. The representative experimental values for the plasma parameters show that, due to the presence of dust particles, the well-known stability of the drift wave in a sheared slab geometry does not hold. However, a radially varying transverse (to the equilibrium magnetic field) velocity field is found to play a key role in stabilizing this instability.
Guaranteed-cost control of a linear uncertain system with multiple time-varying delays: an LMI approach

The guaranteed-cost control program via memoryless state feedback controllers is studied for a class of linear time varying delay systems with norm-bounded time varying parametric uncertainty and a given quadratic cost function. The time varying delays considered are assumed bounded but no information to be available. Sufficient conditions for the existence of guaranteed-cost controllers are given in terms of linear matrix inequalities (LMIs). A convex optimisation problem with LMI constraints is formulated to design the optimal guaranteed-cost controller which minimises the guaranteed cost of the closed-loop uncertain system.
Behavior of monocrystalline silicon under cyclic microindentations with a spherical indenter

This study discusses the behavior of high-pressure phases of monocrystalline silicon when subjected to cyclic indentations with a spherical indenter. It was found that specific phases form in the second and subsequent indentation cycles under low maximum loads. An increase of the maximum indentation load causes changes of subsequent indentation cycles of the phase transformation events to occur earlier on both loading and unloading. The repeated indentations result in the formation of a multiphase structure in the deformed zone, featuring a nonhysteresis behavior. After a critical stage, the properties of the transformed material are stabilized and further indentations can no longer alter the load–displacement curve. It was also found that the greater the maximum load, the faster the occurence of property stabilization.
An improved sufficient condition for stabilisation of unstable first-order processes by observer-state feedback

This work considers the stabilisation and control of unstable first-order linear systems subject to a relatively large I/O time delay. First, it is proposed an observer strategy to predict a specific internal signal in the process. The adequate prediction convergence is obtained and formally stated. Then, it is proposed an estimated state feedback control. Necessary and sufficient stability conditions with respect to time delay size and unstable time constant are provided. The proposed control strategy allows to address time delays as large as four times the unstable time constant of the open-loop system, in contrast with most of the reported related literature. Numerical examples are used for illustrating the parametric stabilisation region as a function of the time delay.
Understanding quantification of microvascularity with high-frequency power Doppler ultrasound

High-frequency power Doppler imaging of angiogenesis can be challenging given the presence of small blood vessels and slow flow velocities. In the presence of substantial Doppler artifacts such as false-positive color pixels or undetected vessels, color pixel density (CPD) and related vascularity metrics do not provide accurate estimates of vascular volume fraction. As a step towards improved microvascular quantification, flow-phantom experiments were performed to establish relationships between CPD and wall filter cut-off velocity for various combinations of vessel size (160, 200, 250, 300, and 360 μm), flow velocity (4, 3, 2, 1, and 0.5 mm/s), and transducer frequency (30 and 40 MHz). Three distinct regions were observed in plots of CPD versus wall filter cut-off velocity: overestimation of CPD at low cut-offs, underestimation of CPD at high cut-offs, and a plateau at intermediate cut-offs. The CPD at the plateau closely matched the phantom's actual vascular volume fraction. The length of the plateau corresponded with the flow-detection performance of the Doppler system, which was assessed using receiver operating characteristic analysis. Color pixel density versus wall filter cut-off curves from analogous in vivo experiments exhibited the same shape, including a distinct CPD plateau. The similar shape of the flow-phantom and in vivo curves suggests that the presence of a plateau can be used to identify the best-estimate CPD value in an in vivo experiment. The ability to identify the best CPD estimate is expected to improve quantification of angiogenesis and anti-angiogenic treatment responses with power Doppler.
Basing Intention-to-Treat on Cause and Effect Criteria

Statisticians often employ the intention-to-treat principle in clinical trials to address any possible bias if subjects are dropped from the analysis data set because of events that might be caused by treatment, for example, protocol violations or missing data. However, there are issues that occur in actual trials that lead to concern about and confusion in identifying a full analysis set for an intention-to-treat analysis. An approach clarifying the problems and suggesting solutions is to consider the finite population induced by randomization. Achieving a balance of observed data from a specific randomization and the unobserved data (counterfactuals) from other possible randomizations is the main principle. In some cases, subsets from the population of all treatment-subject cases can be identified as reduced populations, retaining the cause and effect structure. Corresponding reduced analysis sets, which are subsets of all randomized subjects, can be selected for inference to reduced populations. With a reduced analysis set, unbiased statistics for the reduced population’s parameters may be constructed. A subset of all randomized subjects can be arguably superior for the analysis of cause and effect, since it is more consistent with the intended population and its scientific procedures and measurements.
Skin Texture Recognition using Medical Diagnosis

This paper proposes an automated system for recognizing disease conditions of human skin in context to medical diagnosis. The disease conditions are recognized by analyzing skin texture images using a set of normalized symmetrical Grey Level Co occurrence Matrices (GLCM). GLCM defines the probability of grey level i occurring in the neighborhood of another grey level j at a distance d in directionθ. Directional GLCMs are computed along four directions: horizontal (θ = 0°), vertical (θ = 90°), right diagonal (θ = 45°) and left diagonal (θ = 135°), and a set of features viz. Contrast, Homogeneity and Energy computed from each, are averaged to provide an estimation of the texture class. The system is tested using 225 images pertaining to three dermatological skin conditions viz. dermatitis, eczema, urticaria. An accuracy of 94.81% is obtained using a multilayer perceptron (MLP) as a classifier.
Feedback loops in engineering models of binaural listening

Hearing models for tasks like auditory scene analysis or sound-quality judgments can run into severe problems when acting in a purely bottom-up, that is, signal driven manner, as they may have to follow up on all possible output options until a final decision has been taken. This may lead to a combinatorial explosion. A way out is the inclusion of top-down, that is, hypothesis-driven processes. In top-down processing, the number of states to be evaluated can be reduced substantially, when the system knows what to look for and thereby focuses attention on states which make sense in a given specific situation. To implement adequate top-down processes, various feedback loops will be included in current models, some more specific, others more general. The general ones originate from the concept that the listener model ("artificial listener") actively explores acoustic scenes and thereby develops its aural world in an autonomous way. Following this notion, it is attempted to model listeners according to the autonomous-agents paradigm, where agents actively learn and listen.
Output Feedback Strict Passivity of Discrete-time Nonlinear Systems and Adaptive Control System Design

Abstract In this paper, a necessary and sufficient condition for a discrete-time nonlinear system to be strictly passive is derived and OFSP (Output Feedback Strictly Passive) conditions will be established. Based on the obtained OFSP conditions, an adaptive output feedback controller design method which can solve causality problems will be proposed for a discrete-time nonlinear system.
Quasi‐Linear Geostatistical Theory for Inversing

A quasi-linear theory is presented for the geostatistical solution to the inverse problem. The archetypal problem is to estimate the log transmissivity function from observations of head and log transmissivity at selected locations. The unknown is parameterized as a realization of a random field, and the estimation problem is solved in two phases: structural analysis, where the random field is characterized, followed by estimation of the log transmissivity conditional on all observations. The proposed method generalizes the linear approach of Kitanidis and Vomvoris (1983). The generalized method is superior to the linear method in cases of large contrast in formation properties but informative measurements, i.e., there are enough observations that the variance of estimation error of the log transmissivity is small. The methodology deals rigorously with unknown drift coefficients and yields estimates of covariance parameters that are unbiased and grid independent. The applicability of the methodology is demonstrated through an example that includes structural analysis, determination of best estimates, and conditional simulations.
On Subsets with Intersections of Even Cardinality

This paper solves a question posed by P. Erdös: If A1, A2, …, A are distinct subsets of n elements and if |Ai ∩ Ai| ≡ 0 mod 2 (i ≠ j), then and for each n, there exists a collection of subsets which achieves this bound with equality.
Rough-fuzzy set approach for color and texture based image segmentation

Image segmentation is one of the most attractive problems in image processing. In image segmentation how to extract useful features from image has become crucial. However, color feature or texture feature, which are both wildly used features, could not process segmentation problem alone very well, especially when images are complex. We adopt a rough-fuzzy set approach, which can properly process high dimensionality, for image segmentation considering both color and texture features. This approach firstly constructs a structure named fuzzy data cube, whose attributes are composed of the fuzzy sets associated with image features. The fuzzy data cube, which can be two-dimension or high-dimension, is as the basic data structure in this method. A definition of the membership function of similarity relation based rough-fuzzy set is introduced as well as the definition of dependency function to evaluate the importance of an attribute for image segmentation. Then we used the rough-fuzzy set to discover the similarity set in fuzzy data cube to obtain the segmentation result. Experiments on mosaic and natural images are presented to demonstrate the effectiveness of the proposed method.
Rocking chair defect generation in nanowire growth

We report the observation of a different defect generation phenomenon in layer-by-layer crystal growth. Steps at a nanowire liquid-solid growth interface, resulting from edge nucleated defects, are found to cause a gradual multiplication of stacking faults in the regions bounded by two edge defects. In the presence of a twin boundary, these generated defects continue to propagate along the entire nanowire length. This rocking chair generation mechanism is a unique feature of nanoscale layer-by-layer growth and is significantly different from well-known defect multiplication mechanisms in bulk materials.
The Ordering of Polarons in the Holstein–t-J Model: An Application to La2-xSrxNiO4+y

The recently observed ordering of polarons in La2-xSrxNiO4+y is investigated in terms of a simple one-band model of strongly correlated electrons at quarter filling. The lattice distorsions are described by an in-plane breathing mode which is treated in the adiabatic limit. We use exact diagonalization techniques on small lattices to obtain the ground-state configuration and the excitation spectrum of the Holstein–t-J model. For large enough electron-phonon coupling a state resembling the observed ordering of polarons appears as the ground state of the Holstein–t-J model. We discuss the dependence of the charge and magnetic structure factors on doping away from quarter filling. Within the limits of a finite-lattice calculation our results agree qualitatively with the experiment.
Primary motor cortex activity reduction under the regulation of SMA by real-time fMRI

Real-time fMRI (rtfMRI) is a new technology which allows human subjects to observe and control their own BOLD signal change from one or more localized brain regions during scanning. Current rtfMRI-neurofeedback studies mainly focused on the target region itself without considering other related regions influenced by the real-time feedback. However, there always exits important directional influence between many of cooperative regions. On the other hand, rtfMRI based on motor imagery mainly aimed at somatomotor cortex or primary motor area, whereas supplement motor area (SMA) was a relatively more integrated and pivotal region. In this study, we investigated whether the activities of SMA can be controlled utilizing different motor imagery strategies, and whether there exists any possible impact on an unregulated but related region, primary motor cortex (M1). SMA was first localized using overt finger tapping task, the activities of SMA were feedback to subjects visually on line during each of two subsequent imagery motor movement sessions. All thirteen healthy participants were found to be able to successfully control their SMA activities by self-fit imagery strategies which involved no actual motor movements. The activation of right M1 was also found to be significantly reduced in both intensity and extent with the neurofeedback process targeted at SMA, suggestive that not only the part of motor cortex activities were influenced under the regulation of a key region SMA, but also the increased difference between SMA and M1 might reflect the potential learning effect.
Polarization degrees of freedom in optical pattern forming systems: alkali metal vapour in a single-mirror arrangement

The use of polarization degrees of freedom in optimizing the conditions for optical pattern formation is investigated by discussing the particular example of single-mirror feedback systems. It is demonstrated that in a quasi-scalar saturable medium pattern formation may be completely suppressed by the interplay of saturation and diffusion. This effect takes place for the optical pumping nonlinearity between Zeeman ground states in alkaline vapour cells. It is shown that these limitations can be circumvented by introducing additional polarization components either in the input beam or in the feedback beam. The latter is achieved by introducing polarization-changing elements such as a quarter-wave plate in the feedback loop. In the optimized scheme, pattern formation is obtained with rather low thresholds. Thus, investigations with a rather high aspect ratio and far beyond threshold become feasible.
Rheology of dilute and semidilute noncolloidal hard sphere suspensions

The dissipative behavior of model suspensions composed of non-Brownian, inertialess, rigid spheres immersed in Newtonian and viscoelastic matrices is investigated in the range of volumetric concentrations up to 10%, thus encompassing both the dilute and semidilute regimes. Polymethylmethacrylate beads are dispersed into polyisobutylene, characterized by a Newtonian rheology, and into two viscoelastic polydimethylsiloxanes. Both steady state viscosity and oscillatory shear loss modulus measurements are performed. As expected, the presence of the filler increases both the viscosity and the loss modulus of all suspensions. Following the hydrodynamic calculations of Batchelor, the concentration dependence is described by a second order polynomial expansion in the volume fraction. For low concentrations, the linear Einstein and Palierne predictions for Newtonian and viscoelastic fluids are found to be well obeyed by both the Newtonian and the viscoelastic suspensions. In the semidilute regime, the experimental.
Vibrational Analysis of Organic Molecules Encapsulated in Carbon Nanotubes by Tip-Enhanced Raman Spectroscopy

Tip-enhanced Raman spectroscopy revealed the nanoscale chemical properties of organic molecules encapsulated in single-wall carbon nanotubes (SWNTs). Our approach is based on an enhanced electric field near a laser-irradiated metal tip functioning as a Raman excitation source. The enhanced field can successfully act on encapsulated molecules through the walls of the SWNTs to extract molecular vibrational information. β-carotene, which exhibits several active Raman modes under visible light illumination, was used as the encapsulated molecule. Tip-enhanced Raman spectra measured at seven different positions on SWNT bundles showed that β-carotene molecules inside the tubes were not uniformly distributed. We also found that the filling rate and peak position of the radial breathing mode of the SWNTs are linearly correlated.
Room-temperature ferromagnetism in epitaxial Mg-doped SnO2 thin films

The magnetic behavior of epitaxial Mg-doped SnO2 thin films prepared by radio-frequency magnetron sputtering was investigated in this work. Room-temperature ferromagnetism with the saturation magnetization of about 6.9 emu/cm3 was observed in 6% Mg-doped SnO2 samples. And the saturation magnetization decreases when further doped to 8%, while the optical band-gap increases. The room-temperature ferromagnetism was induced by the holes created by Mg on the substitutional site. Additionally, Mg interstitials and oxygen vacancies play an important role in reducing the magnetic moments.
Vortex-induced vibrations of a sphere

There are many studies on the vortex-induced vibrations of a cylindrical body, but almost none concerned with such vibrations for a sphere, despite the fact that tethered bodies are a common configuration. In this paper, we study the dynamics of an elastically mounted or tethered sphere in a steady flow, employing displacement, force and vorticity measurements. Within a particular range of flow speeds, where the oscillation frequency ($f$) is of the order of the static-body vortex shedding frequency ($f_{vo})$, there exist two modes of periodic large-amplitude oscillation, defined as modes I and II, separated by a transition regime exhibiting non-periodic vibration. The dominant wake structure for both modes is a chain of streamwise vortex loops on alternating sides of the wake. Further downstream, the heads of the vortex loops pinch off to form a sequence of vortex rings. We employ an analogy with the lift on an aircraft that is associated with its trailing vortex pair (of strength $\Gamma^*$ and spacing $b^*$), and thereby compute the rate of change of impulse for the streamwise vortex pair, yielding the vortex force coefficient ($\cvortex$): \[ \cvortex = \frac{8}{\pi} {U^*_{v}}b^*( - \Gamma^*). \] This calculation yields predicted forces in reasonable agreement with direct measurements on the sphere. This is significant because it indicates that the principal vorticity dynamics giving rise to vortex-induced vibration for a sphere are the motions of these streamwise vortex pairs. The Griffin plot, showing peak amplitudes as a function of the mass–damping ($m^*\zeta$), exhibits a good collapse of data, indicating a maximum response of around 0.9 diameters. Following recent studies of cylinder vortex-induced vibration, we deduce the existence of a critical mass ratio, $m^*_{crit} {\approx} 0.6$, below which large-amplitude vibrations are predicted to persist to infinite normalized velocities. An unexpected large-amplitude and highly periodic mode (mode III) is found at distinctly higher flow velocities where the frequency of vibration ($f$) is far below the frequency of vortex shedding for a static body. We find that the low-frequency streamwise vortex pairs are able to impart lift (or transverse force) to the body, yielding a positive energy transfer per cycle.
Model predictive control-based non-linear fault tolerant control for air-breathing hypersonic vehicles

In this study, a model predictive control (MPC)-based fault tolerant control (FTC) design method for air-breathing hypersonic vehicles (AHVs) is proposed. The non-linear model of AHVs is recalled and the FTC problem is discussed. The problem is challenging because the relationship between flight dynamics and the control input is not so clear. For the purpose of non-linear FTC, an optimisation-based reference reconfiguration method is given. Through the reconfiguration, a new reference command, which can be realised by the faulty system, is constructed. Actuator saturation has been take into account when constructing the new reference command. An MPC-based controller reconfiguration method is proposed with respect to the new command and system faults. Finally, simulations are given to show the effectiveness of the proposed control method.