Miracle-dz/UniFAR-FTUs huggingface dataset:
Experimental Measurements of Ingestion Through Turbine Rim Seals—Part I: Externally Induced Ingress

Part I of this two-part paper presented experimental results for externally-induced (EI) ingress, where the ingestion of hot gas through the rim seal into the wheel-space of a gas turbine is controlled by the circumferential variation of pressure in the external annulus. In Part II, experimental results are presented for rotationally-induced (RI) ingress, where the ingestion is controlled by the pressure generated by the rotating fluid in the wheel-space. Although EI ingress is the common form of ingestion through turbine rim seals, RI ingress or combined ingress (where EI and RI ingress are both significant) is particularly important for double seals, where the pressure asymmetries are attenuated in the annular space between the inner and outer seals. In this paper, the sealing effectiveness was determined from concentration measurements, and the variation of effectiveness with sealing flow rate was compared with theoretical curves for RI ingress obtained from an orifice model. Using a nondimensional sealing parameter phio the data could be collapsed onto a single curve, and the theoretical variation of effectiveness with phio was in very good agreement with the data for a wide range of flow rates and rotational speeds. It was shown that the sealing flow required to prevent RI ingress was much less than that needed for EI ingress, and it was also shown that the effectiveness of a radial-clearance seal is significantly better than that for an axial-clearance seal for both EI and RI ingress.
Dynamical behavior of solutions of a semilinear heat equation with nonlocal singularity

The heat equation with a nonlocal nonlinearity $u_t = u_{xx} + {{\varepsilon \| {u( \cdot ,t)} \|^q } / {(1 - u)}},0 0$, subject to $u(0,t) = u(1,t) = 0$ is studied. Stability-instability is analyzed and finite time quenching results are given. Discussions are also extended to more general problems.
The Fueling of Nuclear Activity. I. A Near-Infrared Imaging Survey of Seyfert and Normal Galaxies

We present near-infrared, modified K-band images of a sample of Seyfert and control galaxies. Our sample includes all known Seyfert galaxies in the Revised Shapely-Ames Catalog and Sandage & Tammann's 1987 extension to the RSA with recessional velocities less than 5000 km s-1 and logarithmic axial ratios less than 0.2 (excluding the two early-type Seyfert galaxies Centaurus A and Perseus A). A control sample of normal galaxies, matched to the Seyfert sample in Hubble type, redshift, inclination, and blue luminosity, has also been observed. To quantify the incidence of bars in both samples, elliptical fits to the isophotes of each galaxy have been performed. In agreement with earlier studies, we find that many galaxies classified as unbarred in the optical, display evidence for bars in the near-infrared.
Internal waves around a body moving in a compressible density-stratified fluid

A body is started from rest and moves on an arbitrary path in an inviscid isothermal compressible atmosphere. The phase configuration of the internal waves and the gravity-modified acoustic waves which are generated by the body is studied using small amplitude wave theory. When the body moves at supersonic speeds and the background density gradient approaches zero, it is shown how the wave solutions approach the pure acoustic wave solutions of Lilley et al. (1953).
Ultradiscrete Painlevé II equation and a special function solution

Ultradiscretization with parity variables, which keeps the information of original variables’ sign, is applied to the q-Painlevé II equation of type A6 (q-PII). A special solution of the resulting ultradiscrete system, which corresponds to the special function solution of q-PII, is constructed. Ultradiscrete analogues of the q-Airy equation and its special solutions are also discussed in the process.
A comparison of the 0.1-17 keV/e ion composition in the near equatorial magnetosphere between quiet and disturbed conditions

Data from the plasma composition experiment on ISEE 1 were used to investigate the relative number densities and energy characteristics of H+, He++, He+, and O+ in the near-equatorial magnetosphere at L ≤ 12 during magnetically quiet and disturbed conditions. The ‘quiet’ data were selected on the basis of both Dst and Kp over ∼5 day periods preceeding the data accumulations, and the ‘active’ data were from periods of Dst ≲ −100γ. The ions included in this study had energies in the range of 0.1 ≤ E/Q ≲ 17 keV/e. The data naturally subdivide into two largely different sets in terms of a dipole L parameter. (1) At L ≲ 5 the ion density is dominated by three species, H+, O+, and He+, appearing in variable ratios. The He++ is a small component and is generally obscured by background counts caused by penetrating MeV electrons. The O+ is the most abundant species in well over half of the plasma samples, whereas the H+ is more abundant in the remaining samples. No sample with statistically significant counts shows He+ to be the most abundant ion, although the He+ exceeds the H+ in density in several cases. The O+/H+ and He+/H+ ratios increase toward the inner edge of the ring current population and are, on the average, highest during quiet conditions. Both of these features are qualitatively consistent with a decay process dominated by charge exchange, but a comparison with published charge exchange rates seems to imply that other processes are also involved. All three ion species have a similar mean energy (∼2–7 keV) within the energy window of the experiment, and all three have a low-energy component (0.1 ≤ E/Q ≲ 1 keV/e) that usually dominates the number density at the inner edge, at about L ∼ 3–4 during quiet conditions and L ∼ 2–3 during disturbed conditions. (2) At L > 5 all four species may be present simultaneously in highly variable ratios, but the H+ is usually the most abundant, particularly during quiet conditions. As a rule, the O+/H+ and He+/H+ ratios decrease with increasing L, whereas the He++/H+ ratio slowly increases. Typical values in the outer magnetosphere (L ∼ 10–12) are 1–3% for the He++/H+ and He+/H+ ratios during both quiet and disturbed conditions, whereas the O+/H+ ratio may range from below 1% to over 200%, depending on the magnetic activity level. The highest O+/H+ ratios are found here during the early main phase of magnetic storms, which is contrary to the conditions at L < 5. The H+, O+, and He+ all have a similar mean energy in this region (∼4–6 keV), whereas the He++ is 2-3 times more energetic.
The strict bounded real lemma for linear time-varying systems

Presents a strict bounded real lemma for linear time-varying systems in the infinite-horizon case. Using some operator methods, the authors show that the strict bounded realness for the related I/O operators is equivalent to the solvability of a semidefinite or definite Riccati equation. The authors also apply this result to the problem of disturbance attenuation and H/sub /spl infin//-optimization. All the authors' results include current ones in literature for linear time-invariant systems.
Efficient methodologies for real-time image restoration

In this thesis we investigate the problem of image restoration. The main focus of our research is to come up with novel algorithms and enhance existing techniques in order to deliver efficient and effective methodologies, applicable in real-time image restoration scenarios. Our research starts with a literature review, which identifies the gaps in existing techniques and helps us to come up with a novel classification on image restoration, which integrates and discusses more recent developments in the area of image restoration. With this novel classification, we identified three major areas which need our attention. The first developments relate to non-blind image restoration. The two mostly used techniques, namely deterministic linear algorithms and stochastic nonlinear algorithms are compared and contrasted. Under deterministic linear algorithms, we develop a class of more effective novel quadratic linear regularization models, which outperform the existing linear regularization models. In addition, by looking in a new perspective, we evaluate and compare the performance of deterministic and stochastic restoration algorithms and explore the validity of the performance claims made so far on those algorithms. Further, we critically challenge the necessity of some complex mechanisms in Maximum A Posteriori (MAP) technique under stochastic image deconvolution algorithms. The next developments are focussed in blind image restoration, which is claimed to be more challenging. Constant Modulus Algorithm (CMA) is one of the most popular, computationally simple, tested and best performing blind equalization algorithms in the signal processing domain. In our research, we extend the use of CMA in image restoration and develop a broad class of blind image deconvolution algorithms, in particular algorithms for blurring kernels with a separable prop-
A study of a large sociogram II. Elimination of free parameters

A sociogram is a net in which individuals are nodes and the relations of interest are directed line segments connecting pairs of individuals. In the simplest case such a relation is characterized only by its presence or absence, e.g., “A chooses (or does not choose) B as a friend of a given rank order. ” Mathematical praperties of such nets are of interest to the mathematical sociologist. If the number of individuals is very large, the properties of interest are statistical properties. Here it is shown that two parameters (whose values are obtainable directly from the data) are sufficient to describe certain features of sociograms of junior high schoal children.
Infernal Variables and Dissipative Structures

The formalism of internal state variables is established when gradients of these variables are involved, thus allowing for a spatial localization of dissipative effects that give rise to dissipative structures. Three illustrative cases are briefly sketched out: nematic liquid crystals, localization of damage coupled to elasticity or plasticity, and localization of plastic strains in plasticity with hardening
Observed vibration patterns of clarinet reeds.

It has been shown that a resonance of the reed contributes significantly to the playing behavior of the single‐reed woodwind [S. C. Thompson, J. Acoust. Soc. Am. 66, 1299–1307 (1979)]. As an extended object, the reed is actually expected to possess many resonances, and these have been predicted in FEA calculations [D. Casadonte, J. Acoust. Soc. Am. 94, 1807(A) (1993)] and observed in vibration spectra of isolated reeds [D. H. Keefe and S. Waeffler, J. Acoust. Soc. Am. 94, 1833–1834(A) (1993)]. The current study used holographic interferometry to identify the vibration patterns of a clarinet reed mounted on a mouthpiece, as driven by an acoustic field internal to the mouthpiece. Without a player’s lips to shorten the vibrating section, the lowest frequency and most easily driven resonance is in the region 1500 to 2000 Hz and corresponds to the lowest mode of a rod clamped at one end. The second and third resonances are near 4000 Hz. The second mode displays twisting motion, but with a surprising degree of asymmetry, while the third mode is similar to the second mode of a rod clamped at one end.
Some problems of the qualitative theory of non-linear degenerate second-order parabolic equations

CONTENTSIntroduction Chapter I. Existence and uniqueness of generalized solutions of the Cauchy problem and of initial boundary-value problems ? 1.1. Theorems of existence and non-existence ? 1.2. Uniqueness theorems Chapter II. Estimates and differential properties of generalized solutions ? 2.1. The character of the dependence on the data ? 2.2. Regularity and non-regularity Chapter III. Behaviour of generalized solutions for small values of time ? 3.1. Finite rate of propagation of perturbations ? 3.2. Inertia ? 3.3. Shrinking of the size of the support Chapter IV. Behaviour of generalized solutions for large values of time ? 4.1. Stabilization in finite time ? 4.2. Localization of perturbations ? 4.3. Asymptotic formulae References
High-performance metal-semiconductor-metal InGaN photodetectors using CaF2 as the insulator

The authors report on the high-performance metal-semiconductor-metal (MSM) photodetectors (PDs) fabricated on high-quality InGaN film by introducing a superwide bandgap calcium fluoride (CaF2) as the insulator. The dark current of the PDs with CaF2 is drastically reduced by six orders of magnitude compared with those without CaF2, resulting in an extremely high discrimination ratio larger than 106 between ultraviolet and visible light. The responsivity at 338 nm is as high as 10.4 A/W biased at 2 V, corresponding to a photocurrent gain around 40. The CaF2 layer behaves as an excellent insulator for the InGaN-based MSM-PDs in dark condition, while it allows the electron injection through the metal/semiconductor interface under ultraviolet illumination, contributing to the photocurrent gain without sacrificing the response time (∼ms).
Application of Vortex Lattice Method and Surface Spline Function in Terrain-Induced Wind Field

A numerical simulation method for the wind field over complex terrain is developed in this paper. The complex terrain is represented by a surface, which is established by the surface spline method basing on the contour line of the map. Then it is divided into panels containing vortex ring singularities. The singularity distribution is solved by combining with the potential flow theory and the boundary condition of terrain surface. Finally, the wind field is simulated by linear superposition of the uniform stream and the induced velocity of vortex rings. A numerical example is studied, and the result indicates that the method proposed in this paper could describe the terrain much more accurately and provide a reasonable result of wind field distribution, but has a simple and efficient procedure, which is suitable for the engineering use in flight dynamics.
Microwave vector radiative transfer equation of a sea foam layer by the second‐order Rayleigh approximation

The microwave vector radiative transfer (VRT) equation of a coated spherical bubble layer is derived by means of the second‐order Rayleigh approximation field when the microwave wavelength is larger than the coated spherical particle diameter. Meanwhile, the perturbation method is developed to solve the second‐order Rayleigh VRT equation for the small ratio of the volume scattering coefficient to the extinction coefficient. As an example, the emissive properties of a sea surface foam layer, which consists of seawater coated bubbles, are investigated. The extinction, absorption, and scattering coefficients of sea foam are obtained by the second‐order Rayleigh approximation fields and discussed for the different microwave frequencies and the ratio of inner radius to outer radius of a coated bubble. Our results show that in the dilute limit, the volume scattering coefficient decreases with increasing the ratio of inner radius to outer radius and decreasing the frequencies. It is also found that the microwave emissivity and the extinction coefficient have a peak at very thin seawater coating and its peak value decreases with frequency decrease. Furthermore, with the VRT equation and effective medium approximation of densely coated bubbles, the mechanism of sea foam enhancing the emissivity of a sea surface is disclosed. In addition, excellent agreement is obtained by comparing our VRT results with the experimental data of microwave emissivities of sea surface covered by a sea foam layer at L‐band (1.4 GHz) and the Camps' model.
Pitch of the Residue

The residue is defined as the joint perception of a number of Fourier components. Depending on circumstances outside the scope of this paper, it has a pronounced pitch. The consequences of this phenomenon for the theory of hearing are briefly reviewed in the light of past experiments. Special attention is then called to what are termed the first and second effects of pitch shift. The first effect is found when equidistantly shifting the entire Fourier spectrum. The second effect shows itself primarily in a slight drop in pitch when increasing the frequency spacing of the Fourier components. Presented are rather extensive measurements of these effects for a spectrum consisting of three components. Their inherent connection is shown along with their mathematical relationship. As an important experimental finding, the ambiguity of pitch is presented, measured in two more‐or‐less independent ways. All these phenomena strongly point towards a pitch‐extracting mechanism different from and subsequent to the basilar membrane and operating in the time domain.
The water-ice librational band: radiative transfer model for AFGL 961

On the basis of radiative transfer models we have investigated the librational band of amorphous water-ice (H2O-ice), which might be expected to occur in the spectra of young stellar objects with dust shells, producing an absorption feature at about 13 μm. Models have been run with only bare silicate grains present, together with models including water-ice mantles. We find that the 13-μm feature may be substantially explained without the use of water-ice if laboratory silicates are employed and the 10-μm silicate feature is in self-absorption, a phenomenon which may arise for shells of intermediate optical depth (). The self-absorption process may lead to a variation in the shape of the local minimum between the 10- and 20-μm silicate features, the local minimum occurring at about 13 μm, close to the position of the water-ice librational band. This local minimum could easily be mistaken for the librational water-ice band itself. Nevertheless, the librational band undoubtedly does contribute to the finer details of the shape of the 13-μm absorption feature. We find that for shells of small optical depth the water-ice feature is not distinguishable from the local minimum between the 10- and 20-μm silicate features, while for shells of large optical depth it is washed out completely, so in neither of these two extreme cases should the feature be readily observable. The fact that relatively few objects exist in the intermediate state where the silicate feature is in self-absorption may account for the extremely small number of cases in which the librational band apparently appears as a distinct feature. Radiative transfer models have been produced for the massive pre-main-sequence object AFGL 961E, with the aim of investigating whether the 13-μm feature in its spectrum is due to the librational band of water-ice. Clearly there is water-ice somewhere in the line of sight to AFGL 961, as evidenced by the strong 3.1-μm water-ice band, and the case for the 13-μm feature being due to the librational band is uniquely strong amongst all astronomical objects. However, we present evidence that the grains may have properties similar to laboratory silicates rather than astronomical silicates and that the feature may largely be a manifestation of the 10-μm silicate feature being in self-absorption, with amorphous water-ice being a minor contributor. Neither bare astronomical silicates nor water-ice mantled astronomical silicates will reproduce the 13-μm feature.
Non-isotropic dissipation in non-homogeneous turbulence

On the basis of the two-point velocity correlation equation a new tensor length-scale equation and in turn a dissipation rate tensor equation and the pressure–strain correlation are derived by means of asymptotic analysis and frame-invariance considerations. The new dissipation rate tensor equation can account for non-isotropy effects of the dissipation rate and streamline curvature. The entire analysis is valid for incompressible as well as for compressible turbulence in the limit of small Mach numbers. The pressure–strain correlation is expressed as a functional of the two-point correlation, leading to an extended compressible version of the linear formulation of the pressure–strain correlation. In this turbulence modelling approach the only terms which still need ad hoc closure assumptions are the triple correlation of the fluctuating velocities and a tensor relation between the length scale and the dissipation rate tensor. Hence, a consistent formulation of the return term in the pressure–strain correlation and the dissipation tensor equation is achieved. The model has been integrated numerically for several different homogeneous and inhomogeneous test cases and results are compared with DNS, LES and experimental data.
A STUDY OF WELL-BALANCED FINITE VOLUME METHODS AND REFINEMENT INDICATORS FOR THE SHALLOW WATER EQUATIONS

Water flows can be modelled mathematically and one available model is the shallow water equations. This thesis studies solutions to the shallow water equations analytically and numerically. The study is separated into three parts. The first part is about well-balanced finite volume methods to solve steady and unsteady state problems. A method is said to be well-balanced if it preserves an unperturbed steady state at the discrete level~\cite{NPPN2006}. We implement hydrostatic reconstructions proposed by Audusse et al.~\cite{ABBKP2004} for the well-balanced methods with respect to the steady state of a lake at rest. Four combinations of quantity reconstructions are tested. Our results indicate an appropriate combination of quantity reconstructions for dealing with steady and unsteady state problems~\cite{MR2010}. The second part presents some new analytical solutions to debris avalanche problems~\cite{MR2011DA,MR2012PAAG} and reviews the implicit Carrier--Greenspan periodic solution for flows on a sloping beach~\cite{MR2012CG}. The analytical solutions to debris avalanche problems are derived using characteristics and a variable transformation technique. The analytical solutions are used as benchmarks to test the performance of numerical solutions. For the Carrier--Greenspan periodic solution, we show that the linear approximation of the Carrier--Greenspan periodic solution may result in large errors in some cases. If an explicit approximation of the Carrier--Greenspan periodic solution is needed, higher order approximations should be considered. We propose second order approximations of the Carrier--Greenspan periodic solution and present a way to get higher order approximations. The third part discusses refinement indicators used in adaptive finite volume methods to detect smooth and nonsmooth regions. In the adaptive finite volume methods, smooth regions are coarsened to reduce the computational costs and nonsmooth regions are refined to get more accurate solutions. We consider the numerical entropy production~\cite{Puppo2004} and weak local residuals~\cite{KKP2002} as refinement indicators. Regarding the numerical entropy production, our work is the first to implement the numerical entropy production as a refinement indicator into adaptive finite volume methods used to solve the shallow water equations. Regarding weak local residuals, we propose formulations to compute weak local residuals on nonuniform meshes. Our numerical experiments show that both the numerical entropy production and weak local residuals are successful as refinement indicators. Some publications corresponding to this thesis are listed in the References~\cite{MR2010,MR2011DA,MR2012PAAG,MR2012CG,MR2011NEP,MR2013NEP,MR2011IEEE}. 10.1017/S0004972713000750