Miracle-dz/UniFAR-FTUs huggingface dataset:
Experimental techniques used in topological insulators and realization of quantum spin Hall effect

With the theoretical development and prediction of various topological insulators in two and three dimensions, experimental realization of those topological states and engineering of their characteristics have been hotly pursued, among which the quantum spin Hall effect exhibited in two-dimensional topological insulators have raised lots of concern. This paper aims to firstly give a brief introduction to experimental techniques used in growing and characterizing topological insulators and then we focus on a specific direction, the realization of quantum spin Hall effect, to elucidate one ramification of the experimental progress in the realm of topological insulator. The quantum spin Hall effect distinguishes itself due to its lack of non-magnetic scattering preserved by time reversal symmetry in its edge channels. Thus, materials showing such phenomenon are significantly promising for achieving dissipationless spintronics.
Mechanism and Elimination of Scan Blindness in a T-Printed Dipole Array

In this article, the scan blindness in a T-printed dipole is analyzed, and an elimination strategy is proposed. First, the main cause of scan blindness is analyzed. The scan characteristics are obtained using an active element pattern (AEP) with an infinite rectangular lattice arrangement. Based on the propagation of a guided wave along the antenna row and the electric-field ( $E$ -field) distribution observed during simulations, an equivalent circuit model for a unit cell of the T-printed dipole is obtained. A quasi-transverse electromagnetic (TEM) guided wave is predicted using the dispersion relation curve obtained from the equivalent circuit, and it is proven that the calculated curve is in good agreement with the eigen mode simulations and measured trajectory of the scan blind angle, for different frequencies. Next, slits and stubs are introduced as parasitic structures to eliminate the scan blindness and improve the antenna scan range. To confirm the effects of these parasitic elements, a linear array simulation is performed, which confirms the suppression of a quasi-TEM guided wave. Analysis of the active reflection coefficient and dispersion diagram indicates that the scan characteristics have been improved by the addition of parasitics. Four types of array prototypes are fabricated and their measurements validate the scan blindness prediction and confirm the proposed mechanism of scan blindness and its improvements.
Improvement of the Algorithm Based on Dark Channel Prior Defogging

The dark channel prior defogging algorithm is a method for rough estimation of transmittance. The dark channel prior method is not obvious enough for the sky. The paper uses a rough estimation model based on the relationship between depth of field and transmittance. A dehazing method that makes the transmittance more refined is proposed on a priori basis. The atmospheric light value is calculated from the atmospheric scattering model, and the image is converted from the RGB color space to the HSV color space and the S (saturation) component is extracted as a supplement to the transmittance. The final transmittance is obtained by the method of transmittance fusion, and a clear image is restored according to the atmospheric scattering model. The experimental results show that the method can effectively eliminate the fog, and the restored image better preserves the image details.
Ultrafast optical currents in gapped graphene

We theoretically study the interaction of ultrashort optical pulses with gapped graphene. Such a strong pulse results in a finite conduction band population and a corresponding electric current, both during and after the pulse. Since gapped graphene has broken inversion symmetry, it has an axial symmetry about the y -axis but not about the x-axis. We show that, in this case, if the linear pulse is polarized along the x-axis, the rectified electric current is generated in the y direction. At the same time, the conduction band population distribution in the reciprocal space is symmetric about the x-axis. Thus, the rectified current in gapped graphene has an inter-band origin, while the intra-band contribution to the rectified current is zero.
Optimization of helicopter rotor blade performance by spline-based taper distribution using neural networks based on CFD solutions

ABSTRACT The taper distribution along the span of a helicopter blade is defined using a novel method applied for the first time and considered as the main contribution of this work. This method uses cubic splines to generate modified blade shapes. The thrust and the torque values, computed by a 3-D Reynolds Average Navier Stokes solver, are used to train a Neural Networks based model. After that a constrained optimization is conducted based on this model for two different rotor speeds under hover condition. The optimization variables are the chord lengths at three different span locations: root, mid-span and tip. The optimization constraints are the torque or thrust values of the original blade and the practical limits for the chord lengths. Two optimum cases are investigated: maximum Figure of Merit with greater thrust and maximum Figure of Merit with less torque than the baseline. The major challenge of this work is to use the taper distribution as the only design parameter to obtain comparable results to other studies in literature in which more than one parameter is used. The results show that the Figure of Merit can improve by around 5% and the torque can be reduced by around 20%.
A category theoretic approach to extensions of Banach algebras

This thesis aims to generalise Busby’s framework for studying extensions of C∗-algebras, to the Banach-algebraic setting, without requiring admissibility assumptions on extensions. In the case where the canonical embedding ιJ of a faithful Banach algebra J into its multiplier algebra MJ has closed range, we classify all extensions of an arbitrary Banach algebra B by J. This is done by presenting two categories, one of extensions and another of Busby maps, and proving that these categories are equivalent. We then consider cases where the canonical embedding of J need not have closed range, and provide some partial results in such cases under the extra assumption of a bounded linear lift for a given Busby map. These results are then applied to several examples, where we also compute explicit multiplier norms for MJ when J is a maximal ideal in Ck([−1, 1]). To go further, we study the quotient MJ/ιJ (J) not as a seminormed space but as an object in a suitable derived category. To lay the necessary foundations, the derived category construction of Grothendieck and Verdier is applied to the category of Banach spaces and bounded linear maps. Using this framework, we introduce a class of “Q-Busby maps” from an arbitrary Banach algebra B into MJ/ιJ (J), and obtain a restricted version of Busby’s original correspondence, applicable whenever J is a faithful Banach algebra.
Nonlinear coupled MHD-kinetic particle simulations of heavy impurities in tokamak plasmas

We present a new reference solution for charged particle motion in a strongly inhomogeneous magnetostatic field. The solution describes both bound and unbound particle motion, which can be split into three regimes, the deflection, loop-deflection and drift regime. We calculate the trajectory in terms of trigonometric and hyperbolic functions, resulting in simple analytical expressions for the particle position and ∇B-drift velocity. This reference solution is useful to verify and compare the performance of kinetic and guiding-centre charged particle pushers in inhomogeneous fields, by verifying the conservation of two constants of motion, as well as the exact trajectory at any time.
Retinal vessel segmentation approach based on corrected morphological transformation and fractal dimension

The morphological structure of retinal vessels plays an important role in analysing and diagnosing fundus disease. In this study, an unsupervised automatic segmentation method for retinal blood vessels with corrected morphological transformation and fractal dimension is proposed. To enhance the contrast between retinal vessels and background in a fundus image, the morphological operator with linear structural elements is used; to remove the lesion and its light reflection, a compensation method is proposed; to extract the objects from a grey image, the multi-threshold approach is applied; to recognise the blood vessels and noise from the fundus image, a new method based on fractal dimension is presented. The new approach is tested in detail on three public databases STARE, DRIVE and HRF. Experimental results show that the segmentation algorithm is better than other existing unsupervised automatic segmentation algorithms, and the new approach is robust.
A Wideband Circularly Polarized Array Antenna With Compact and High-Efficiency Feeding Network

A wideband circularly polarized (CP) waveguide array antenna is proposed in this article. The proposed array antenna consists of four antipodally ridged elements and a compact feeding network with two orthogonal septa inserted to a stepped cavity. Both the components are wideband and they can work independently or together. The proposed topology gives a good solution to feed a <inline-formula> <tex-math notation="LaTeX">$2 \times 2$ </tex-math></inline-formula> waveguide subarray which is the basis of large-scale arrays. It exhibits a larger working bandwidth than the array antennas fed by high-order mode cavities. A prototype is fabricated using 3-D printing and milling technologies. Measured results demonstrate a bandwidth of 40.3% from 9.9 to 14.9 GHz, in terms of the reflection coefficients less than −15 dB and the axial ratios smaller than 3 dB. An expanded <inline-formula> <tex-math notation="LaTeX">$8 \times 8$ </tex-math></inline-formula> CP array antenna is explored based on the proposed <inline-formula> <tex-math notation="LaTeX">$2 \times 2$ </tex-math></inline-formula> subarray to show the potentials of our design, and a total efficiency over 78% within a bandwidth of 38.7% is obtained by simulation.
Precision measurements of Hausdorff dimensions in two-dimensional quantum gravity

Two-dimensional quantum gravity, defined either via scaling limits of random discrete surfaces or via Liouville quantum gravity, is known to possess a geometry that is genuinely fractal with a Hausdorff dimension equal to 4. Coupling gravity to a statistical system at criticality changes the fractal properties of the geometry in a way that depends on the central charge of the critical system. Establishing the dependence of the Hausdorff dimension on this central charge c has been an important open problem in physics and mathematics in the past decades. All simulation data produced thus far has supported a formula put forward by Watabiki in the nineties. However, recent rigorous bounds on the Hausdorff dimension in Liouville quantum gravity show that Watabiki’s formula cannot be correct when c approaches . Based on simulations of discrete surfaces encoded by random planar maps and a numerical implementation of Liouville quantum gravity, we obtain new finite-size scaling estimates of the Hausdorff dimension that are in clear contradiction with Watabiki’s formula for all simulated values of . Instead, the most reliable data in the range is in very good agreement with an alternative formula that was recently suggested by Ding and Gwynne. The estimates for display a negative deviation from the latter formula, but the scaling is seen to be less accurate in this regime.
The use of systems engineering principles for the integration of existing models and simulations

With the rise in computational power, the prospect of simulating a complex engineering system with a high degree of accuracy and in a meaningful way is becoming a real possibility. Modelling and simulation have become ubiquitous throughout the engineering life cycle, as a consequence there are many thousands of existing models and simulations that are potential candidates for integration. This work is concerned with ascertaining if systems engineering principles are of use in the support of virtual testing, from desire to test, designing experiments, specifying simulations, selecting models and simulations, integrating component parts, verifying that the work is as specified, and validating that any outcomes are meaningful. A novel representation of systems engineering framework is proposed and forms the bases for the methods that were developed. It takes the core systems engineering principles and expresses them in a way that can be implemented in a variety of ways. An end to end process for virtual testing with the potential to use existing models and simulations is proposed, it provides structure and order to the testing task. A key part of the proposed process is the recognition that models and simulations requirements are different from those of the system being designed, and hence a modelling and simulation specific writing guide is produced. The automation of any engineering task has the potential to reduce the time to market of the final product, for this reason the potential of natural language processing technology to hasten the proposed processes was investigated. Two case studies were selected to test and demonstrate the potential of the novel approach, the first being an investigation into material selection for a squash ball, and the second being automotive in nature concerned with combining steering and braking systems. The processes and methods indicated their potential value, especially in the automotive case study where inconsistences were identified that could have otherwise affected the successful integration. This capability, combined with the verification stages, improves the confidence of any model and simulation integration. The NLP proof of concept software also demonstrated that such technology has value in the automation of integration. With further testing and development there is the possibility to create a software package to guide engineers through the difficult task of virtual testing. Such a tool would have the potential to drastically reduce the time to market of complex products.
Silicon microdosimetry in hadron therapy using Geant4

Hadron therapy, referring to treating cancer with protons and heavier ions, provides many advantages over conventional X-ray radiotherapy, including better dose conformity and dose sparing to healthy tissue. One open problem associated with hadron therapy is that the radiobiological effectiveness (RBE), which is an important input parameter in the clinical treatment planning, changes significantly along the Bragg peak/spread out Bragg peak. It is paramount to be able to estimate the RBE to improve the treatment in terms of clinical outcome. The solution proposed by the Centre For Medical Radiation Physics (CMRP), University of Wollongong, is given by silicon-based microdosimetry technology, which offers a powerful solution to estimate the RBE with sub-mm spatial resolution. Such high spatial resolution is particularly important at the distal edge of the Bragg peak/spread out Bragg peak where organs at risk may be positioned. Microdosimetry is conventionally performed using tissue equivalent proportional counters which feature complex and bulky operation and do not achieve a sub-mm spatial resolution. Silicon microdosimetry offers a more simple compact design, which is more well suited to the sharp dose gradients of hadron therapy beams and for routine quality assurance measurements. However, silicon microdosimetry is not without its difficulties, namely the measurement is not tissue equivalent and the design is not angularly independent. This thesis describes the in-silico characterisation and design optimisation of novel silicon microdosimeters developed at the CMRP. The study has been performed by means of the Geant4 Monte Carlo Toolkit, which has been validated against experimental measurements in this project to quantify its accuracy for hadron therapy and for microdosimetric studies. The tissue equivalence and angular dependence have been investigated. A method to convert the response of the detector from silicon to tissue was developed, which is now routinely used at the CMRP to convert experimental microdosimetric measurements to tissue, in proton and carbon ion therapy. Due to the strong directionality of hadron therapy beams and the angular dependence of the silicon microdosimeter designs, it was found that the traditional method of converting the energy deposition to lineal energy using the mean chord length of the silicon sensitive volumes (SVs) of the device was inappropriate. Instead, the mean path length was found
Do Covariates Change the Estimand?

Abstract Adjustment for covariates has been underused in trials intended to support approval of medical products. This underuse results partly from confusion about whether adjusting changes the thing being estimated or only the estimate of it, and partly from misplaced concerns about assumptions of the analysis. If the thing being estimated is carefully defined, it is seen that adjustments can be used with minimal assumptions. Thus, the benefit of increased efficiency can be realized with essentially no cost in robustness or interpretability.
Deriving and verifying a general granular locomotion scaling law

The complexities of granular materials make modeling the interactions between grains and solid intruders, such as a wheel, incredible difficult. Often, modeling these interactions requires discrete particle simulation methods, such as the Discrete Element Method (DEM), a process that is prohibitively computationally intensive for large systems. The difficulty of modeling granular materials has posed great difficulty for design engineers, particularly those interested in granular locomotion, since there is no way to gain predictive insight into the performance of a given granular locomotion system. A granular locomotion scaling law was developed, which instructs how to scale size, mass, and driving parameters in order to relate dynamic behaviors of different locomotors in the same granular media. For the development of this scaling relationship, a general wheel operating in an ideal Coulombic material was considered. Through dimensional analysis, the system was described as a function of a set of dimensionless numbers which are ratios of the dimensional parameters of the system. From the dimensionless description of the system, a set of scaling families are derived, where each member of a family has the same dimensionless inputs but different dimensional parameters. Then, DEM simulations were used to verify that each member of a given scaling family had the same dimensionless outputs. The DEM simulations found a high level of agreement between the dimensionless outputs of systems in the same scaling family, demonstrating the predictive power of the granular locomotion scaling law. Thesis Supervisor: Ken Kamrin Title: Associate Professor of Mechanical Engineering
Impacts of Assimilating High-Resolution Atmospheric Motion Vectors Derived from Himawari-8 on Tropical Cyclone Forecast in HWRF

The impact of the assimilation of high spatial and temporal resolution atmospheric motion vectors (AMVs) on tropical cyclone (TC) forecasts has been investigated. The high-resolution AMVs are derived from the full disk scan of the new generation geostationary satellite Himawari-8. Forecast experiments for three TCs in 2016 in a western North Pacific basin are performed using the National Centers for Environmental Prediction (NCEP) operational Hurricane Weather Research and Forecasting Model (HWRF). Two different ensemble–variational hybrid data assimilation configurations (using background error covariance created by global ensemble forecast and HWRF ensemble forecast), based on the Gridpoint Statistical Interpolation (GSI), are used for the sensitivity experiments. The results show that the inclusion of high-resolution Himawari-8 AMVs (H8AMV) can benefit the track forecast skill, especially for long-range lead times. The diagnosis of optimal steering flow indicates that the improved track forecast seems to be attributed to the improvement of initial steering flow surrounding the TC. However, the assimilation of H8AMV increases the negative intensity bias and error, especially for short-range forecast lead times. The investigation of the structural change from the assimilation of H8AMV revealed that the following two factors are likely related to this degradation: 1) an increase of inertial stability outside the radius of maximum wind (RMW), which weakens the boundary layer inflow; and 2) a drying around and outside the RMW. Assimilating H8AMV using background error covariance created from HWRF ensemble forecast contributes to a significant reduction in negative intensity bias and error, and there is a significant benefit to TC size forecast.
Head Pulsation Signal Analysis for 3-Axis Head-Worn Accelerometers

Previously, using single-axis accelerometers, it has been proposed that in conditions such as traumatic brain injury (TBI) the brain pulsation signal characteristics change, potentially due to changes induced by the impact to the brain. In this paper, we aim to validate the use of a custom built embedded measurement system towards the analysis of the head pulsation signals. The system comprises of several synchronized high sampling rate 3-axis accelerometers and a simultaneous chest ECG. In our case three accelerometers on the surface of human head are used (in left temple, forehead and right temple), while the subject were in supine position. To illustrate that a proper signal quality may be extracted, we derive heart rate (HR) and heart rate variability (HRV) from each sensor and each axis for each of five healthy male volunteers. The results are reported against ECG as the ground truth. This study will build ground for further clinical trial utilizing multi-axial accelerometers to study both healthy and diseased subjects (e.g. TBI patients).
Fusion par lisseur de Kalman pour l’estimation de la fréquence respiratoire à partir de l’électrocardiogramme ou du photoplethysmogramme

Ce memoire de these vise a proposer de nouvelles methodes robustes pour l'estimation de la frequence respiratoire (FR) a partir des signaux physiologiques souvent utilises dans la clinique comme l'electrocardiogramme (ECG) ou le photoplethysmogramme (PPG), tout en evitant de porter des capteurs encombrants et inconfortables. En effet, la respiration influence les signaux ECG et/ou PPG. Plusieurs modulations qui decrivent la respiration sont extraites basee principalement sur l'amplitude, la frequence et la ligne de base. Il est toutefois difficile de determiner la combinaison optimale des modulations pour obtenir une estimation precise de la FR en raison du bruit, la specificite de chaque patient et de l'activite. Apres une revue de la litterature, il ressort que peu de travaux ont etudie la qualite de ces modulations. Nous proposons donc de quantifier la qualite des modulations a l'aide d'indices de qualite respiratoire (IQR), un nouvel indice base sur une modulation sinusoidale est introduit. Puis, deux methodes sont proposees: la premiere selectionne automatiquement la modulation avec l'IQR le plus eleve pour une estimation de la FR, la seconde combine les deux meilleurs modulations avec le lisseur de Kalman (LK). Une nouvelle approche de fusion de modulations basee sur un modele multimodale est egalement exploree. Ces methodes sont evaluees sur trois bases de donnees de differents contextes cliniques: la surveillance dans les soins postoperatoires (ou les patients sont immobiles), le suivi pendant les activites physiques quotidiennes et la surveillance neonatale. Les resultats experimentaux montrent que les IQRs associes a un algorithme de fusion augmentent la precision de l'estimation de la FR a partir des modulations derivees et montrent des resultats superieurs aux travaux issus de la litterature.