Miracle-dz/UniFAR-FTUs huggingface dataset:
Infinite dimensional stochastic calculus via regularization

This paper develops some aspects of stochastic calculus via regularization to Banach valued processes. An original concept of $\chi$-quadratic variation is introduced, where $\chi$ is a subspace of the dual of a tensor product $B \otimes B$ where $B$ is the values space of some process $X$ process. Particular interest is devoted to the case when $B$ is the space of real continuous functions defined on $[-\tau,0]$, $\tau>0$. Ito formulae and stability of finite $\chi$-quadratic variation processes are established. Attention is deserved to a finite real quadratic variation (for instance Dirichlet, weak Dirichlet) process $X$. The $C([-\tau,0])$-valued process $X(\cdot)$ defined by $X_t(y) = X_{t+y}$, where $y \in [-\tau,0]$, is called {\it window} process. Let $T >0$. If $X$ is a finite quadratic variation process such that $[X]_t = t$ and $h = H(X_T(\cdot))$ where $H:C([-T,0])\longrightarrow \R$ is $L^{2}([-T,0])$-smooth or $H$ non smooth but finitely based it is possible to represent $h$ as a sum of a real $H_{0}$ plus a forward integral of type $\int_0^T \xi d^-X$ where $H_{0}$ and $\xi$ are explicitly given. This representation result will be strictly linked with a function $u:[0,T]\times C([-T,0])\longrightarrow \R$ which in general solves an infinite dimensional partial differential equation with the property $H_{0}=u(0, X_{0}(\cdot))$, $\xi_{t}=D^{\delta_{0}}u(t, X_{t}(\cdot)):=Du(t,X_{t}(\cdot))(\{0\})$. This decomposition generalizes the Clark-Ocone formula which is true when $X$ is the standard Brownian motion $W$. The financial perspective of this work is related to hedging theory of path dependent options without semimartingales.
Finite element/mode-matching analysis of ferrite/dielectric line junctions of arbitrary cross-section

Abstract This paper is focused on the analysis of line junctions obtained as a cascade of dielectric and ferrite guides of arbitrary cross-section. The main application of such structures is nonreciprocal devices such as isolators, circulators, or phase shifters. The efficient finite element/mode-matching approach is proposed to the analysis of such structures. In this approach, the finite element method is applied to determine propagation coefficients and field distributions in cross-sections of the structure. Then using mode-matching technique the scattering parameters of investigated junction are calculated. Since, all the field integrals required in mode-matching are evaluated in the pre-processing stage of finite element method, only small numerical effort is required to calculate scattering parameters of the junction. The numerical efficiency of proposed approach is examined for different geometries of longitudinally magnetized shielded ferrite coupled line junction. Obtained results are compared with the ones calculated using commercial software and presented in literature. A very good agreement is achieved.
Insights into convective momentum transport and its parametrization from idealized simulations of organized convection

Deep convection is a multiscale process that influences the budgets of heat, moisture and momentum significantly. In global climate models, the thermodynamic effects of convection are normally treated by parametrization schemes, with a separate formulation for convective momentum transport (CMT). The schemes for current thermodynamic and momentum parametrizations are based on upright entraining plume models that do not account for vertically tilted mesoscale circulations, which characterize organized convection in sheared environments. The associated countergradient vertical transport of horizontal momentum fundamentally affects dynamical interactions between the convection and the mean flow. This study examines the CMT properties of simulated idealized mesoscale convective systems, including their sensitivity to horizontal resolution, domain size and lateral boundary conditions. It is found that, even for large domains, the horizontal gradient terms are important, especially the mesoscale pressure gradients, which are neglected in CMT parametrizations. A nonlinear analytic model provides a dynamical foundation for the effects of convective organization, including the role of the horizontal pressure gradient. It is found that a small computational domain affects the convective organization adversely by generating artificially large compensating subsidence and an unrealistic evolution of CMT. Finally, analyses of the cross‐updraught/downdraught pressure gradients expose significant uncertainties in their representation in contemporary CMT parametrization schemes.
Noise covariance estimation in low-level computer vision

In image processing literature, thus far researchers have assumed the perturbation in the data to be white (or uncorrelated) having a covariance matrix σ2I, i.e., assumption of equal variance for all the data samples and that no correlation exists between the data samples. However, there has been very little attempt to estimate noise characteristics under the assumption that there is correlation between data samples. We develop a new and novel approach for the estimation of the unknown colored noise covariance matrix. We use the facet model to describe the noise free image, because of its simple, yet elegant mathematical formulation. Original contributions of this dissertation include: (1) Development of a new and novel approach for the simultaneous estimation of the unknown colored (or correlated) noise covariance matrix and the hyperparameters of the covariance model using the facet model . We also estimate, simultaneously, coefficients of the facet model. (2) Introduction of the Generalized Inverted Wishart ( GJW ) distribution to the image processing and computer vision community. (3) Formulation of the problem solution in a Bayesian framework using an improper uniform prior distribution for the facet model coefficients (i.e. a flat prior) and a Generalized Inverted Wishart ( GJW ) prior distribution for the unknown noise covariance matrix that is to be estimated. (4) Placing a structure on the hypercovariance matrix of GJW distribution, such that its elements are a function of the coefficients of a correlation filter. These filter coefficients in addition to the number of degrees of freedom parameter of the GJW distribution are called the hyperparameters. (5) Hyperparameters have constraints placed on them so that the resulting hypercovariance matrix remains positive definite. Therefore, we designed a new extension of the expectation maximization algorithm called the generalized constrained expectation maximization (GCEM) algorithm for the estimation of the hyperparameters using the sequential unconstrained minimization technique (SUMT) via barrier functions to incorporate the constraints. (6) Development of a new ridge operator called the integrated second directional derivative ridge operator (ISDDRO) based on the facet model. Our main focus here is the optimal estimation of ridge orientation. The orientation bias and orientation standard deviation are the measures of performance. The latter measures the noise sensitivity. (7) Comparison of ISDDRO using the noise covariance matrix estimation (ISDDRO-CN) with the same ridge operator under white noise assumption (ISDDRO-WN) and also with the most competing ridge operator multilocal level set extrinsic curvature (MLSEC) [5]. ISDDRO-CN has superior noise sensitivity characteristics compared to both ISDDRO-WN and MLSEC.
Rising bubbles in yield stress materials

We present an experimental investigation of bubbles rising in elasto-viscoplastic media. The effects of medium rheology and bubble size on the bubble velocity and shape are investigated. In addition, a discussion regarding the influence of the stress history on the bubble path is presented. Experimental tests are performed using yield stress materials which also present elastic behavior. Despite the difficulty in determining the relative importance of the different forces that are present in this flow, the results obtained illustrate the effect of yield stress, inertia, elasticity, and buoyancy on the dynamics and shape of the bubble.
Solar Illumination Control of the Polar Wind

Polar wind outflow is an important process through which the ionosphere supplies plasma to the magnetosphere. The main source of energy driving the polar wind is solar illumination of the ionosphere. As a result, many studies have found a relation between polar wind flux densities and solar EUV intensity, but less is known about their relation to the solar zenith angle at the ionospheric origin, certainly at higher altitudes. The low energy of the outflowing particles and spacecraft charging means it is very difficult to measure the polar wind at high altitudes. We take advantage of an alternative method that allows estimations of the polar wind flux densities far in the lobes. We analyze measurements made by the Cluster spacecraft at altitudes from 4 up to 20 RE. We observe a strong dependence on the solar zenith angle in the ion flux density and see that both the ion velocity and density exhibit a solar zenith angle dependence as well. We also find a seasonal variation of the flux density.
The Role of Double Inversion Recovery Sequence in Detecting Gray Matter Lesions in patients with Multiple Sclerosis Using 3Tesla MRI

* Medical Collage/ Al-Nahrain University. Consultant Radiologist in Al-Imamian AlKadhimyian Medical City. **Permanent Radiologist in Al-Imamian AlKadhimyian Medical City. disease of the central nervous system that typically affects the white matter of the brain and spinal cord, mainly in a periventricular distribution . Demyelination occurs in discriminative foci, termed plaques which range in size from a few millimeters to a few centimeters and are typically peri-venular . ABSTRACT : BACKGROUND: In the recent time, the sequence used to delineate gray matter lesions is Double Inversion Recovery (DIR), with the use of this sequence in high magnetic field (3 Tesla machine). OBJECTIVE: To detect and localize gray matter lesions in patients with established multiple sclerosis using DIR sequence in 3 Tesla MRI. Also to compare the detection rate of white matter lesions by the use of DIR versus Fluid Attenuation Inversion Recovery (FLAIR) sequence. PATIENTS AND METHODS: A prospective study included 54 patients with established diagnosis of multiple sclerosis of more than 3 years duration was conducted from April 2014 to January 2015. The study was done in the MRI units of Al-Yarmouk Teaching Hospital and Al-Imamian Al-Kadhimian Medical City. All patients were examined with the following MRI imaging sequences: T2WI axial, T2 FLAIR sagittal and coronal, T1 axial and sagittal, DIR axial and coronal. T1 Sagittal and axial were repeated after giving IV contrast and examined after 30 minutes postcontrast. Gray matter lesions were classified according to Peterson and Bo model. Statistical analysis conducted by using Excel 2013 version. RESULTS: Fifty four patients with established diagnosis of MS (43 patients with relapsing remitting MS and 11 patients with secondary progressive MS) were included. Of the 54 patients, 39 patients (72.2%) patients have positive gray matter lesion. The 39 patients with positive gray matter lesions are classified as follows: 26 patients (66.5%) had sub-pial lesions, 9 patients (23%) had leucocortical lesions, 3 patients (7.5%) showed entirely cortical lesions, and finally the whole cortex is involved in 1 patient only (2.5%). The insular cortex was the most commonly involved region seen in 14 patients (35.8%), followed by the thalamic lesions. Among the 39 patients with positive 9 patients (16.5%) had additional deep nuclei lesions. Total number of lesions detected by DIR (320 lesions) was largely greater than the total number of lesions detected by FLAIR (185 lesions). CONCLUSION: DIR is a sensitive sequence for detection of gray matter lesion, DIR is more sensitive than FLAIR in detection of white matter lesions and cortical gray matter lesions are more commonly encountered than deep nuclei lesions.
Stochastic stability of elastic and viscoelastic columns

The problem of the stochastic stability of elastic and viscoelastic columns compressed by a Gaussian white noise axial force is addressed in the context of the dynamic stability. The former column has proportional damping, the other has both proportional damping and viscoelastic damping with memory expressed by the superposition integral. The stability is checked in statistical moments by examining the eigenvalues of the matrix of the coefficients of the ODE ruling the time evolution of them, which are obtained by means of Ito’s differential rule.
Multi-task learning for captioning images with novel words

Recent captioning models are limited in their ability to describe concepts unseen in paired image-sentence pairs. This study presents a framework of multi-task learning for describing novel words not present in existing image-captioning datasets. The authors' framework takes advantage of external sources-labelled images from image classification datasets, and semantic knowledge extracted from the annotated text. They propose minimising a joint objective which can learn from these diverse data sources and leverage distributional semantic embeddings. When in the inference step they change the BeamSearch step by considering both the caption model and language model enabling the model to generalise novel words outside of image-captioning datasets. They demonstrate that in the framework by adding an annotated text data which can help the image captioning model to describe images with the right corresponding novel words. Extensive experiments are conducted on both AI Challenger and Microsoft coco (MSCOCO) image captioning datasets of two different languages, demonstrating the ability of their framework to describe novel words such as scenes and objects.
Physico-chemical induced modification of seed germination and early development in artichoke (Cynara scolymus L.) using low energy plasma technology

In this study, low pressure non-thermal radiofrequency nitrogen plasma at very low power has been used to treat the artichoke seeds on the powered cathode for the first time. The influence of treatment time on the surface physical properties, germination rate, seedling growth, and enzyme activity of the seeds has been investigated. Results showed that plasma treatment considerably improved the germination rate and seedling growth. The root length grew by 28.5% and 50% and root dry weight increased by 13% and 53%, respectively, for 10 and 15 min of treatment. The same trend has been found for the shoot growth parameters although the greater stimulatory efficacy on root has been obtained. The nitrogen plasma treatment substantially made the seeds' surface hydrophilic which leads to 36.9% improvement in seed's water uptake at 15 min of treatment. Our study showed the activity of peroxidase and catalase enzymes slightly increased after the plasma treatment.
Passive magnetic shielding by machinable MgB2 bulks: measurements and numerical simulations

We report on a combined experimental and modelling approach towards the design and fabrication of efficient bulk shields for low-frequency magnetic fields. To this aim, MgB2 is a promising material when its growing technique allows the fabrication of suitably shaped products and a realistic numerical modelling can be exploited to guide the shield design. Here, we report the shielding properties of an MgB2 tube grown by a novel technique that produces fully machinable bulks, which can match specific shape requirements. Despite a height/radius aspect ratio of only 1.75, shielding factors higher than 175 and 55 were measured at temperature T = 20 K and in axially-applied magnetic fields μ0Happl = 0.1 and 1.0 T, respectively, by means of cryogenic Hall probes placed on the tube’s axis. The magnetic behaviour of the superconductor was then modelled as follows: first we used a two-step procedure to reconstruct the macroscopic critical current density dependence on magnetic field, Jc(B), at different temperatures from the local magnetic induction cycles measured by the Hall probes. Next, using these Jc(B) characteristics, by means of finite-element calculations we reproduced the experimental cycles remarkably well at all the investigated temperatures and positions along the tube’s axis. Finally, this validated model was exploited to study the influence both of the tube’s wall thickness and of a cap addition on the shield performance. In the latter case, assuming the working temperature of 25 K, shielding factors of 105 and 104 are predicted in axial applied fields μ0Happl = 0.1 and 1.0 T, respectively.
Observed best prediction via nested-error regression with potentially misspecified mean and variance

We consider the observed best prediction (OBP; Jiang, Nguyen and Rao 2011) for small area estimation under the nested-error regression model, where both the mean and variance functions may be misspecified. We show via a simulation study that the OBP may significantly outperform the empirical best linear unbiased prediction (EBLUP) method not just in the overall mean squared prediction error (MSPE) but also in the area-specific MSPE for every one of the small areas. A bootstrap method is proposed for estimating the design-based areaspecific MSPE, which is simple and always produces positive MSPE estimates. The performance of the proposed MSPE estimator is evaluated through a simulation study. An application to the Television School and Family Smoking Prevention and Cessation study is considered.
Van Allen Probes observations of cross‐scale coupling between electromagnetic ion cyclotron waves and higher‐frequency wave modes

We present observations of higher‐frequency (~50–2500 Hz, ~0.1–0.7 fce) wave modes modulated at the frequency of colocated lower frequency (0.5–2 Hz, on the order of fci) waves. These observations come from the Van Allen Probes Electric Field and Waves instrument's burst mode data and represent the first observations of coupling between waves in these frequency ranges. The higher‐frequency wave modes, typically whistler mode hiss and chorus or magnetosonic waves, last for a few to a few tens of seconds but are in some cases observed repeatedly over several hours. The higher‐frequency waves are observed to be unmodulated before and after the presence of the electromagnetic ion cyclotron (EMIC) waves, but when the EMIC waves are present, the amplitude of the higher‐frequency waves drops to the instrument noise level once every EMIC wave cycle. Such modulation could significantly impact wave‐particle interactions such as acceleration and pitch angle scattering, which are crucial in the formation and depletion of the radiation belts. We present one case study with broadband, high‐frequency waves observed to be modulated by EMIC waves repeatedly over a 2 h time span on both spacecraft. Finally, we show two additional case studies where other high‐frequency wave modes exhibit similar modulation.
A critical contraction frequency in lymphatic vessels: transition to a state of partial summation

A Critical Contraction Frequency in Lymphatic Vessels: Transition to a State of Partial Summation. (August 2006) Joshua Keith Meisner, B.S., Texas A&M University Chair of Advisory Committee: Dr. Christopher M. Quick Although lymphatic vessel behavior is analogous to hearts (e.g. systole and diastole) and blood vessels (e.g. basal tone), hearts and blood vessels have fundamentally different contractile properties. While summation during contraction is minimized in the heart, summation is necessary for tonic contraction in blood vessels. Because lymphatic vessel behavior mimics cardiac and vascular behavior, we hypothesized that above a critical contraction frequency there is significant summation, evidenced by significantly increased diastolic active tension (i.e. basal tone). We used an isovolumic, controlled-flow preparation to examine the interaction of contraction cycletime with contraction frequency. Using segments of isolated lymphatic vessels (~1 cm in length and 3-4 mm in diameter) from bovine mesentery, we measured transmural pressure and diameter for end-diastole and end-systole during spontaneous contractions for 10 volume steps. We found time between contractions (beat-to-beat period) decreases with increasing diameter, and total contraction time (vessel twitch length, 11.08 ± 1.54 s) slightly increases with increasing diameter. At the intersection of these relationships, there is a critical period, below which the vessel does not have time to fully relax. Above the diameter at the critical period, diastolic active tension (end-
Turbulent horizontal convection under spatially periodic forcing: a regime governed by interior inertia

Differential heating applied at a single horizontal boundary forces ‘horizontal convection’, even when there is no net heat flux through the boundary. However, almost all studies of horizontal convection have been limited to a special class of problem in which temperature or heat flux differences were applied in only one direction and over the horizontal length of a box (the Rossby problem; Rossby, Deep-Sea Res., vol. 12, 1965, pp. 9–16). These conditions strongly constrain the flow. Here we report laboratory experiments and direct numerical simulations (DNS) extending the results of Griffiths & Gayen (Phys. Rev. Lett., vol. 115, 2015, 204301) for horizontal convection forced by boundary conditions imposed in a two-dimensional periodic array at a horizontal boundary. The experiments use saline and freshwater fluxes at a permeable base with the imposed boundary salinity having a horizontal length scale one quarter of the width of the box. The flow reaches a state in which the net boundary buoyancy flux vanishes and the bulk of the fluid shows an inertial range of turbulence length scales. A regime transition is seen for increasing water depth, from an array of individual coherent plumes on the forcing scale to convection dominated by emergent larger scales of overturning. The DNS explore the analogous thermally forced case with sinusoidal boundary temperature of wavenumber $n=4$ , and are used to examine the Rayleigh number ( $Ra$ ) dependence for shallow- and deep-water cases. For shallow water the flow transitions with increasing $Ra$ from laminar to turbulent boundary layer regimes that are familiar from the Rossby problem and which have normalised heat transport scaling as $Nu\sim Ra^{1/5}$ and $Nu\sim (Ra\,Pr)^{1/5}$ , with $Nu$ the Nusselt number and $Pr$ the Prandtl number, in this case maintaining a stable array of coherent turbulent plumes. For deep-water and large $Ra$ the laminar scaling transitions to $Nu\sim (Ra\,Pr)^{1/4}$ , with the scales of turbulence extending to the dimensions of the box. The $1/4$ power law regime is explained in terms of the momentum of symmetric, inviscid large scales of motion in the interior coupled to diffusive loss of heat through stabilised parts of the boundary layer. The turbulence production is predominantly by shear instability rather than convection, with viscous dissipation distributed throughout the bulk of the fluid. These conditions are not seen in the highly asymmetric flow in the Rossby problem even at Rayleigh numbers up to six orders of magnitude greater than the transition found here. The new inertial interior regime has the rate of supply of available potential energy, and its removal by mixing of density, increasing as $Ra^{5/4}$ , which is faster than $Ra^{6/5}$ in the Rossby problem. Irreversible mixing is confined close to the forcing boundary and is very much larger than the viscous dissipation, which is proportional to $Ra$ .