Miracle-dz/UniFAR-FTUs huggingface dataset:
Theoretical investigation of very high-quantum-efficiency segmented crystalline detectors for low-contrast visualization in megavoltage cone-beam CT

Megavoltage cone-beam computed tomography (CBCT) using active matrix flat-panel imagers (AMFPIs) is a promising candidate for providing image guidance in radiation therapy. Unfortunately, the practical clinical implementation of this technique is limited by the relatively low detective quantum efficiency (DQE) of conventional megavoltage AMFPIs. This limitation is due to the modest thickness of the phosphor screen employed to convert incident x-rays to optical photons and the trade-off that exists between phosphor thickness and spatial resolution. Recently, our group has begun pursuing the development of thick crystalline segmented scintillating detectors as x-ray converters for AMFPIs so as to circumvent this limitation. In order to examine the potential of such detectors for providing soft-tissue visualization by means of CBCT at megavoltage energies, a Monte Carlo-based method was used to simulate the acquisition of projection images of a contrast phantom. These images were used to perform CT reconstructions by means of a Feldkamp-based algorithm. In this study, various detector configurations involving CsI and BGO scintillators at thicknesses of 10 mm and 40 mm were evaluated. In addition, since the simulations only considered energy deposition, and did not include optical phenomena, both segmented and non-segmented (continuous) detector configurations were evaluated. For the segmented CsI detectors, septal wall materials with densities lower, equivalent and higher than that of the scintillator were considered. Performance was quantified in terms of the contrast-to-noise ratio obtained for lowcontrast, soft-tissue-equivalent objects (i.e., liver, brain, and breast) embedded in the phantom. The results obtained from these early studies suggest that such segmented converters can provide visualization of soft-tissue contrast in tomographic images at clinically practical doses. It is anticipated that the realization of optimized segmented detector designs will lead to clinically useful megavoltage AMFPIs exhibiting impressive performance.
ONE-SIDED DIVISION ABSOLUTE VALUED ALGEBRAS

We develop a structure theory for left divsion absolute valued algebras which shows, among other things, that the norm of such an algebra comes from an inner product. Moreover, we prove the existence of left division complete absolute valued algebras with left unit of arbitrary infinite hilbertian division and with the additional property that they have nonzero proper closed left ideals. Our construction involves results from the representation theory of the so called "Canonical Anticommutation Relations" in Quantum Mechanics. We also show that homomorphisms from complete normed algebras into arbitrary absolute valued algebras are contractive, hence automatically continuous.
A Low Pressure Turbine at Extreme Off-Design Operation

In a cooperative project between the Institute of Aircraft Propulsion Systems and MTU Aero Engines GmbH, a two-stage low pressure turbine with integrated 3D airfoil and endwall contouring is tested. The experimental data taken in the altitude test-facility study the effect of high incidence in off-design operation. Steady measurements are covering a wide range of Reynolds numbers between 40,000 and 180,000. The results are compared with steady multistage CFD predictions with a focus on the stator rows. A first unsteady simulation is taken into account as well. The CFD simulations include leakage flow paths with disk cavities modeled. Compared to design operation the extreme off-design high-incidence conditions lead to a different flow-field Reynolds number sensitivity. Airfoil lift data reveals changing incidence with Reynolds number of the second stage. Increased leading edge loading of the second vane indicates a strong cross channel pressure gradient in the second stage leading to larger secondary flow regions and a more three-dimensional flow-field. Global characteristics and area traverse data of the second vane are discussed. The unsteady CFD approach indicates improvement in the numerical prediction of the predominating flow-field.
A note on computational efficiency in asymptotically distribution-free correlational models

Asymptotically distribution-free (ADF) methods for the analyses of covariances or correlations require the calculation of an estimated variance–covariance matrix of those covariances or correlations. Formulae for this variance–covariance matrix are well known from the literature. However, it turns out that, in particular for the correlations, this matrix is quite elaborate because it seems to be necessary to compute and store fourth-order standardized sample moments. In this paper we show that this can be avoided and that computations can be done in the data matrix directly. This may save a lot of core storage and computation time as well.
The Topology of Symmetric

We study the topology of symmetric, second-order tensor fields. The goal is to represent their complex structure by a simple set of carefully chosen points and lines analogous to vector field topology. We extract topological skeletons of the eigenvector fields, and we track their evolution over time. We study tensor topological transitions and correlate tensor and vector data. The basic constituents of tensor topology are the degenerate points, or points where eigenvalues are equal to each other. Degenerate points play a similar role as critical points in vector fields. We identify two kinds of elementary degenerate points, which we call wedges and trisectors. They can combine to form more familiar singularities-such as saddles, nodes, centers, or foci. However, these are generally unstable structures in tensor fields. Finally, we show a topological rule that puts a constraint on the topology of tensor fields defined across surfaces, extending to tensor fields the PoincarC-Hopf theorem for vector fields.
UvA-DARE ( Digital Academic Repository ) ISO spectroscopy of young intermediate-mass stars in the BD + 40 degrees 4124 group

We present the results of ISO SWS and LWS grating scans towards the three brightest members of the BD+40 ◦4124 group in the infrared: BD+40 ◦4124 (B2Ve), LkHα 224 (A7e) and the embedded source LkH α 225. Emission from the pure rotational lines of H2, from ro-vibrational transitions of CO, from PAHs, from Hi recombination lines and from the infrared fine structure lines of [Fe ii], [Si ii], [S i], [O i], [O iii] and [Cii] was detected. These emission lines arise in the combination of a low-density ( ≈ 102 cm−3) H ii region with a clumpy PDR in the case of BD+40 ◦4124. The lower transitions of the infrared H i lines observed in BD+40 ◦4124 are optically thick; most likely they arise in either a dense wind or a circumstellar disk. This same region is also responsible for the optical H i lines and the radio continuum emission. In the lines of sight towards LkHα 224 and LkHα 225, the observed emission lines arise in a non-dissociative shock produced by a slow ( ≈ 20 km s−1) outflow arising from LkHα 225. Toward LkHα 225 we also observe a dissociative shock, presumably located closer to the outflow source than the non-dissociative shock. In the line of sight towards LkHα 225 we observed absorption features due to solid water ice and amorphous silicates, and due to gas-phase H2O, CO and CO2. No solid CO2 was detected towards LkH α 225, making this the first line of sight where the bulk of the CO 2 is in the gas-phase.
Reversible axial-strain effect and extended strain limits in Y-Ba-Cu-O coatings on deformation-textured substrates

The dependence of transport critical-current density Jc on axial tensile strain e was measured at 76 K and self-magnetic field for YBa2Cu3O7−δ (YBCO) coatings on buffered, deformation-textured substrates of pure Ni, Ni–5-at. %-W, and Ni–10-at. %-Cr–2-at. %-W. Expectations have been that the strain tolerance of these composites would be limited by the relatively low yield strains of the deformation-textured substrates, typically less than 0.2%. However, results show that the irreversible degradation of Jc(e) occurs at a strain equal to about twice the yield strain of the substrate. Therefore, YBCO/Ni-alloy composites may satisfy axial-strain performance requirements for electric devices, including the most demanding applications, motors and generators in which a strain tolerance exceeding 0.25% is needed. Furthermore, the YBCO/Ni–5-at. %-W conductors showed a reversible strain effect, which may be induced by a reversible strain-field broadening around mismatch dislocations at the grain boundaries. This eff.
Point processes and queues, martingale dynamics

I Martingales. - 1. Histories and Stopping Times. - 2. Martingales. - 3. Predictability. - 4. Square-Integrable Martingales. - References. - Solutions to Exercises, Chapter I. - II Point Processes, Queues, and Intensities. - 1. Counting Processes and Queues. - 2. Watanabe's Characterization. - 3. Stochastic Intensity, General Case. - 4. Predictable Intensities. - 5. Representation of Queues. - 6. Random Changes of Time. - 7. Cryptographic Point Processes. - References. - Solutions to Exercises, Chapter II. - III Integral Representation of Point-Process Martingales. - 1. The Structure of Internal Histories. - 2. Regenerative Form of the Intensity. - 3. The Representation Theorem. - 4. Hilbert-Space Theory of Poissonian Martingales. - 5. Useful Extensions. - References. - Solutions to Exercises, Chapter III. - IV Filtering. - 1. The Theory of Innovations. - 2. State Estimates for Queues and Markov Chains. - 3. Continuous States and Nontrivial Prehistory. - References. - Solutions to Exercises, Chapter IV. - V Flows in Markovian Networks of Queues. - 1. Single Station : The Historical Results and the Filtering Method. - 2. Jackson's Networks. - 3. Burke's Output Theorem for Networks. - 4. Cascades and Loops in Jackson's Networks. - 5. Independence and Poissonian Flows in Markov Chains. - References. - Solutions to Exercises, Chapter V. - VI Likelihood Ratios. - 1. Radon-Nikodym Derivatives and Tests of Hypotheses. - 2. Changes of Intensities "a la Girsanov". - 3. Filtering by the Method of the Probability of Reference. - 4. Applications. - 5. The Capacity of a Point-Process Channel. - 6. Detection Formula187 References189 Solutions to Exercises, Chapter VI. - VII Optimal Control. - 1. Modeling Intensity Controls. - 2. Dynamic Programming for Intensity Controls : Complete-Observation Case. - 3. Input Regulation. A Case Study in Impulsive Control. - 4. Attraction Controls. - 5. Existence via Likelihood Ratio. - References. - Solutions to Exercises, Chapter VII. - VIII Marked Point Processes. - 1. Counting Measure and Intensity Kernels. - 2. Martingale Representation and Filtering. - 3. Radon-Nikodym Derivatives. - 4. Towards a General Theory of Intensity. - References. - Solutions to Exercises, Chapter VIII. - A1 Background in Probability and Stochastic Processes. - 1. Introduction. - 2. Monotone Class Theorem. - 3. Random Variables. - 4. Expectations. - 5. Conditioning and Independence. - 6. Convergence. - 7. Stochastic Processes. - 8. Markov Processes. - References. - A2 Stopping Times and Point-Process Histories. - 1. Stopping Times. - 2. Changes of Time and Meyer-Dellacherie's Integration Formula. - 3. Point-Process Histories. - References. - A3 Wiener-Driven Dynamical Systems. - 1. Ito's Stochastic Integral. - 2. Square-Integrable Brownian Martingales. - 3. Girsanov's Theorem. - References. - A4 Stieltjes-Lebesgue Calculus. - 1. The Stieltjes-Lebesgue Integral. - 2. The Product and Exponential Formulas. - References. - General Bibliography.
Isothermal Bias of the “Filter Ratio” Method for Observations of Multithermal Plasma

An early result from the Transition Region and Coronal Explorer (TRACE) was that the EUV filter ratios for many narrow coronal loops (widths of a few arcseconds) were found to cluster within the small range 0.50-1.70, as functions of position along loop length. The most common interpretation is that the temperature along the loop is in fact nearly constant with a value between 1.1 and 1.3 MK. This interpretation has resulted in a class of TRACE loop models with heating close to the footpoints. We analyze the filter ratio method to show that the constant TRACE 195 Å/173 Å ratios can be reproduced by multithermal differential emission measures (DEMs) along the line of sight over a wide range of peak temperatures, so long as the distribution is relatively flat and spans the temperature response of both channels. Furthermore, in the limit of flat (i.e., very multithermal) DEMs, the filter ratio method is biased toward the ratio of the integrals of the temperature response functions. This result is general to any measurement of intensity ratios that are formed over a nonzero temperature range (e.g., narrow passbands and ion emission lines).
Tubular adhesive joints under axial load

In this paper a general study on tubular adhesive joint under axial load is presented. We focus our attention on both static and dynamic behavior of the joint, including shear and normal stresses and strains in the adhesive layer, joint optimization, failure load for brittle crack propagation, and crack detection based on free vibrations. First, we have considered the shear and normal stresses and strains in the adhesive layer to propose an optimization to uniform axial strength (UAS) and to reduce the stress peaks in the bond. The stress analysis confirms that the maximum shear stresses are attained at the ends of the adhesive and that the peak of maximum shear stress is reached at the end of the stiffer tube and does not tend to zero as the adhesive length approaches infinity. A fracture energy criterion to predict brittle crack propagation for conventional and optimized joint is presented. The stability of brittle crack propagation and the strength of the joint, as well as the ductile-brittle failure transition, are analyzed. A detection method to predict crack severity, based on joint dynamic behavior, is also proposed. The crack detection is achieved through the determination of the axial natural frequencies of the joint as a function of the crack length, by determining the roots of a determinantal equation. @DOI: 10.1115/1.1604835#
Quasi-phase-matched second-harmonic generation by backward propagating interaction

Both static and dynamical analyses of quasi-phase-matched second-harmonic generation by backward propagating interaction, where the second-harmonic wave is generated in reflection, are presented. It is shown that bistability appears in the generated second-harmonic power if the amount of phase mismatch is suitably chosen. The bistability also appears in the output fundamental wave, since the cascaded second-order nonlinear process gives rise to the effective self-modulation of the fundamental wave, which can be applied to all-optical signal processing. The output second-harmonic and fundamental powers can be switched between two bistable states by controlling the intensity or phase of the input fundamental wave. >
ATMOSPHERIC GRAVITY WAVES IN THE STRATOSPHERE OF MARS AND THE IONOSPHERES OF JUPITER AND SATURN

of Dissertation Presented to the Graduate School of the University of Florida in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy ATMOSPHERIC GRAVITY WAVES IN THE STRATOSPHERE OF MARS AND THE IONOSPHERES OF JUPITER AND SATURN By Daniel J. Barrow May 2011 Chair: Katia I. Matcheva Major: Physics Atmospheric gravity waves transport energy and momentum from a source region to the location of wave dissipation and are understood to greatly affect the thermal and dynamical structures of the upper atmosphere. Atmospheric gravity waves have been studied extensively on Earth but due to observational limitations the study of these waves in the atmospheres of other planets has been minimal. This work is composed of three different parts that study gravity waves in different planets’ atmospheres. In the Earth atmosphere the spectral characteristics of gravity waves reveal a remarkable universality with respect to time of day, location, topography, and altitude. The first study in this work utilizes the nearly 20,000 temperature profiles from the Mars Global Surveyor (MGS) radio occultation measurements to calculate the power spectral density for gravity waves on Mars and compares them to the observations and theories for the Earth atmosphere. The second part of this work investigates the effects of gravity waves in the ionosphere of Jupiter. This work models a realistic ionosphere that maintains the chemistry and dynamics of multiple ion species in the presence of a propagating gravity wave. It is shown that a wave creates significant variations in the H 3 column density across a horizontal plane of Jupiter. It is argued that the H 3 thermal emission from Jupiter can be used to obtain observations of gravity waves in Jupiter’s ionosphere
Modelling of spanwise mixing in compressor through-flow computations

Abstract Although three-dimensional Navier-Stokes computations are coming into use more and more, streamline curvature through-flow computations are still needed, especially for multistage compressors, and where codes which run in minutes rather than hours are preferred. These methods have been made more realistic by taking account of end-wall effects and spanwise mixing by four aerodynamic mechanisms: turbulent diffusion, turbulent convection by secondary flow, spanwise migration of aerofoil boundary layer fluid and spanwise convection of fluid in blade wakes. This paper describes the models adopted in the DRA streamline curvature method for axial compressor design and analysis. Previous papers are summarized briefly before describing the new part of the model—that accounting for aerofoil boundary layers and wakes. Other changes to the previously published annulus wall boundary layer model have been made to enable it to cater for separations and end bends. The resulting code is evaluated against a range of experimental and computational results.
Using gamma-ray bursts to detect a cosmological density of compact objects

If gamma-ray bursts come from cosmological distances, then a significant fraction of them will be lensed. Multiple images will be detected by the time delays between the two images. The shortest bursts are sensitive to lens masses ≥ 250 M ⊙ . The observed fraction of double images provides a direct measure of Ω(compact) as a function of the assumed maximum redshifts of the burst sources. The results depend weakly on the cosmological model and the burst spectra
Variable Selection in Nonparametric Regression with Continuous Covariates

In a nonparametric regression setup where the covariates are continuous, the problem of estimating the number of covariates will be discussed in this paper. The kernel method is used to estimate the regression function and the selection criterion is based on minimizing the cross-validation estimate of the mean squared prediction error. We consider choosing both the bandwidth and the number of covariates based on the data. Unlike the case of linear regression, it turns out that the selection is consistent and efficient even when the true model has only a finite number of covariates. In addition, we also observe the curse of dimensionality at work.
Designing compact fuzzy rule-based systems with default hierarchies for linguistic approximation

This paper illustrates how a genetic algorithm can be employed for designing a compact fuzzy rule-based system, which linguistically describes a nonlinear function with many inputs in a human understandable manner. First we show that general fuzzy if-then rules with only a few antecedent conditions are necessary for such linguistic modeling when nonlinear functions have many input variables. Next we illustrate a new fuzzy reasoning method for handling fuzzy if-then rules with different specificity levels (i.e., for handling a mixture of general and specific fuzzy if-then rules). The fuzzy reasoning method is formulated based on the concept of default hierarchies of Holland et al.(1986) for calculating output values in a similar manner to human thinking. Then we formulate a rule selection problem for finding a small number of relevant fuzzy if-then rules among a large number of possible combinations of antecedent and consequent linguistic values. The rule selection problem has two objectives: to minimize the prediction error and to minimize the number of selected rules. A genetic algorithm is applied to the rule selection problem. Finally we suggest how genetics-based machine learning approaches (i.e., Pittsburgh and Michigan) can be used for linguistic modeling of nonlinear functions.
Phase retrieval algorithm based on maximum entropy method

The paper presented deals with phase retrieval problem for image reconstruction from only the spectrum magnitude. Only two-dimensional spatially limited nonnegative objects, which are characterized by the analytical spectra, are considered assuming that the unique solution of the phase problem exists. It is proposed to use a nonlinear optimization approach, namely, the maximum entropy method (MEM) which has very good extrapolation features and a high noise stability. For solving the phase retrieval problem we introduce into the optimized entropy functional additional unknowns related to the real and imaginary parts of an object spectrum and represent the constraints, which are derived from measured spectrum magnitude data, as linear constraints, in order to reduce the optimization problem to the standard MEM. The whole computational algorithm is constructed as a combination of the standard MEM algorithm and an additional nonlinear constraint for the real and imaginary parts of the spectrum data which is realized during computational iterations. Images reconstructed by the proposed MEM approach may be, if necessary, further improved by Fienup's (1982) iterations. In this case the previous image is used as a starting point ensuring reliable convergence of Fienup's algorithm. Numerous simulation results demonstrate validity and high efficiency of the approach proposed.
Time domain analysis of sigma delta modulation

A time-domain analysis of sigma-delta modulation with linear filter decoding has been provided. The decoding operation of the 1-b output from a sigma-delta modulator can always be decomposed, and the final output of the decoding filter is the sum of signal term s/sub H/ and noise term n/sub H/. The exact form of s/sub H/ and n/sub H/ has been derived. Two typical sinc and since/sup 2/ digital decoding filters are studied. The only condition imposed on the input x/sub n/ is that x/sub n/ belongs to (-b,b), to avoid overloading the sigma-delta modulator. The results apply even to the case when the signal is not oversampled. <<ETX>>
Distribution of physical clusters

A general formalism is developed to obtain series expansions of the average number of physical clusters of particles in the framework of Mayer's theory. The special case of lattice systems is investigated in more detail and some preliminary results are given on the relation between percolation (namely the formation of an infinite cluster) and condensation in fluid systems in the lowest approximation (summation of chain diagrams).