Time–frequency and time–time filtering with the S-transform and TT-transform

The limitations of frequency-domain filtering methods have motivated the development of alternative techniques, in which a filter is applied to a time–frequency distribution instead of the Fourier spectrum. One such distribution is the S-transform, a modified short-time Fourier transform whose window scales with frequency, as in wavelets. Recently it has been shown that the S-transform's local spectra have time-domain equivalents. Since each of these is associated with a particular window position on the time axis, collectively they give a time–time distribution. This distribution, called the TT-transform, exhibits differential concentration of different frequency components, with higher frequencies being more strongly concentrated around the localization position than lower frequencies. This leads to the idea of filtering on the time–time plane, in addition to the time–frequency plane. Examples of time–frequency filtering and time–time filtering are presented.     

Thermodynamic assessments of the Ni–Pt and Al–Ni–Pt systems

The Ni–Pt system is assessed using the CALPHAD method. The four fcc-based phases, i.e. disordered solid solution phase, Ni₃Pt–L1₂, NiPt–L1₀ and NiPt₃–L1₂, are described by a four-sublattice model. The calculated thermodynamic properties and order/disorder phase transformations are in good agreement with the experimental data. In order to facilitate the assessment, first-principles pseudopotential calculations are also performed to calculate the enthalpy of formation at 0 K, and comparison with the assessed values is discussed. By combining the assessments of Al–Ni and Al–Pt, the Al–Ni–Pt ternary system is assessed within a narrow temperature range, focusing on the fcc-based phases and their phase equilibria with B2 phase.     

Solid–liquid equilibria in the quasi-binary thallium(I) selenide–tin(IV) selenide system

The phase diagram for the quasi-binary Tl₂Se–SnSe₂ system was constructed based on the results of studies by both thermal analysis and X-ray diffraction. The diagram was compared with two other diagrams for the same system published earlier by other authors. The study produced substantial evidence corroborating the formation of two new chemical compounds.     

Pan–tilt–zoom camera calibration and high-resolution mosaic generation

In this paper, we discuss the problem of estimating parameters of a calibration model for active pan–tilt–zoom cameras. The variation of the intrinsic parameters of each camera over its full range of zoom settings is estimated through a two step procedure. We first determine the intrinsic parameters at the camera’s lowest zoom setting very accurately by capturing an extended panorama. The camera intrinsics and radial distortion parameters are then determined at discrete steps in a monotonically increasing zoom sequence that spans the full zoom range of the camera. Our model incorporates the variation of radial distortion with camera zoom. Both calibration phases are fully automatic and do not assume any knowledge of the scene structure. High-resolution calibrated panoramic mosaics are also computed during this process. These fully calibrated panoramas are represented as multi-resolution pyramids of cube-maps. We describe a hierarchical approach for building multiple levels of detail in panoramas, by aligning hundreds of images captured within a 1–12× zoom range. Results are shown from datasets captured from two types of pan–tilt–zoom cameras placed in an uncontrolled outdoor environment. The estimated camera intrinsics model along with the cube-maps provides a calibration reference for images captured on the fly by the active pan–tilt–zoom camera under operation making our approach promising for active camera network calibration.     

Incremental frequency count—a post BWT‐stage for the Burrows–Wheeler compression algorithm

The stage after the Burrows–Wheeler transform (BWT) has a key function inside the Burrows–Wheeler compression algorithm as it transforms the BWT output from a local context into a global context. This paper presents the Incremental Frequency Count stage, a post‐BWT stage. The new stage is paired with a run length encoding stage between the BWT and the entropy coding stage of the algorithm. It offers high throughput similar to a Move To Front stage, and at the same time good compression rates like the strong but slow Weighted Frequency Count stage. The properties of the Incremental Frequency Count stage are compared to the Move To Front and Weighted Frequency Count stages by their compression rates and speeds on the Calgary and large Canterbury corpora. Copyright © 2006 John Wiley & Sons, Ltd.     

Construction of modified embedded atom method potentials for the study of the bulk phase behaviour in binary Pt–Rh, Pt–Pd, Pd–Rh and ternary Pt–Pd–Rh alloys

A first attempt is made to simulate the solid part of the phase diagram of the ternary Pt–Pd–Rh system. To this end, Monte Carlo (MC) simulations are combined with the Modified Embedded Atom Method (MEAM) and optimised parameters entirely based on Density Functional Theory (DFT) data. This MEAM potential is first validated by calculating the heat of mixing or the demixing phase boundary for the binary subsystems Pt–Rh, Pt–Pd and Pd–Rh. For the disordered alloy systems Pt–Rh and Pt–Pd, the MC/MEAM simulation results show a slightly exothermic heat of mixing, thereby contradicting any demixing behaviour, in agreement with other theoretical results. For the Pd–Rh system the experimentally observed demixing region is very well reproduced by the MC/MEAM simulations. The extrapolation of the MEAM potentials to ternary systems is next validated by comparing DFT calculations for the energy of formation of ordered Pt–Pd–Rh compounds with the corresponding MEAM energies. Finally, the validated potential is used for the calculation of the ternary phase diagram at 600 K.     

The generalized matrix product and the wavelet transform

This paper provides a new formulation of wavelet transforms in terms of generalized matrix products. After defining the generalized matrix product, a fast algorithm using parallelism for compactly supported wavelet transforms that satisfym-scale scaling equations form 2 is established. Several special examples, such as the Fourier-wavelet matrix expansion and wavelet decompositions and reconstructions, that demonstrate that the new formulation and algorithm offer unique advantages over existing wavelet algorithms are provided.This research was supported in part by U.S. Air Force contract F08635-89-C-0134.     

A thermodynamic description of the Al–Ca–Zn ternary system

A comprehensive thermodynamic database of the Al–Ca–Zn ternary system is presented for the first time. Critical assessment of the experimental data and re-optimization of the binary Al–Zn and Al–Ca systems have been performed. The optimized model parameters of the third binary system, Ca–Zn, are taken from the previous assessment of the Mg–Ca–Zn system by the same authors. All available as well as reliable experimental data both for the thermodynamic properties and phase boundaries are reproduced within experimental error limits. In the present assessment, the modified quasichemical model in the pair approximation is used for the liquid phase and Al_FCC phase of the Al–Zn system to account for the presence of the short-range ordering properly. Two ternary compounds reported by most of the research works are considered in the present calculation. The liquidus projections and vertical sections of the ternary systems are also calculated, and the invariant reaction points are predicted using the constructed database.     

Thermodynamic modeling of the C–Pu–U system

The ternary C–Pu–U system is thermodynamically assessed to pursue the development of a thermodynamic database for future nuclear fuels. The substitution model was used for the liquid phase, and a two-sublattice model for the PuC–UC monocarbide, PuC₂–UC₂ dicarbide and Pu₂C₃–U₂C₃ sesquicarbide phases. Ternary interaction parameters were adjusted on the experimental information for the phase relationships. Isoplethal and isothermal ternary sections, as well as some liquidus temperatures are calculated and compared with the experimental data. The overall agreement is discussed, and shows that experimental uncertainties still remain.     

On a computationally simple form of the generalized Campbell–Baker–Hausdorff–Dynkin formula

In this paper a computationally simple form of the generalized Campbell–Baker–Hausdorff–Dynkin formula (GCBHD) is given. Simplifications arise from both combinatorial (explicit) as well as algorithmic (implicit) arguments. On generating the Ph. Hall basis in a special form, and introducing a specific structure representation of the vector field, vector fields appearing in GCBHD are automatically transformed into the reduced Ph. Hall basis. The formula can be exploited in nonholonomic motion planning what is illustrated with examples.     

Pre-control form of the generalized Campbell–Baker–Hausdorff–Dynkin formula for affine nonholonomic systems

In this paper a pre-control form of the generalized Campbell–Baker–Hausdorff–Dynkin (gCBHD) formula is presented. This form is dedicated to nonholonomic (affine) systems often encountered in robotics. The simplest possible expression for the pre-control gCBHD is obtained as control-dependent functions pre-multiply elements of the Ph. Hall basis. Algorithmic aspects of deriving the formula are highlighted. An application of the pre-control form of the gCBHD formula in motion planning of nonholonomic systems is also reported.     

Thermodynamic modeling of the Mg–Ge–Pb system

All available thermodynamic and phase diagram data of the Mg–Ge and Mg–Pb binary systems, and the Mg–Ge–Pb ternary system have been critically evaluated and all reliable data have been simultaneously optimized to obtain one set of model parameters for the Gibbs energies of the liquid and all solid phases as functions of composition and temperature. The liquid phase was modeled using the Modified Quasichemical Model in order to describe the strong ordering in Mg–Ge and Mg–Pb liquid. Mg₂Ge–Mg₂Pb solid solution phase was modeled with consideration of a solid miscibility gap. All calculations were performed using the FactSage thermochemical software.     

Improvements to Burrows–Wheeler compression algorithm

In 1994 Burrows and Wheeler presented a new algorithm for lossless data compression. The compression ratio that can be achieved using their algorithm is comparable with the best known other algorithms, whilst its complexity is relatively small. In this paper we explain the internals of this algorithm and discuss its various modifications that have been presented so far. Then we propose new improvements for its effectiveness. They allow us to obtain a compression ratio equal to 2.271 bpc for the Calgary Corpus files, which is the best result in the class of Burrows–Wheeler transform based algorithms. Copyright © 2000 John Wiley & Sons, Ltd.     

Applying the Hough transform pseudo-linearity property to improve computing speed

This work describes a general method of acceleration of the convergence of the Hough transform based, on the one hand, on an improvement of the image analysis speed, and, on the other hand, on the space undersampling of the image. This method is used in image processing to extract lines, circles, ellipses or arbitrary shapes. The results presented are applied to the detection of straight-line segments and ellipses, but can be extended to any type of transform.     

Miniature spherical motor using iron–gallium alloy (Galfenol)

We propose a miniature spherical motor using iron–gallium alloy (Galfenol). This motor consists of four rods of Galfenol with square cross-section, a wound coil, a permanent magnet, an iron yoke and a spherical rotor placed on the edge of the rods. The magnetomotive force of the magnet provides bias magnetostriction for the rods and an attractive force that maintains the rotor on the rods. When currents of 180° phase difference flow in pairs of opposing coils, a torque is exerted on the rotor by pushing (expansion) and pulling (contraction) of the rods. Rotation about a single axis is realized by a sawtooth current, such that the rotor rotates with slow expansion and slips at the rapid contraction. The motor can be fabricated at small sizes and driven with a low voltage, suitable for application as a microactuator for rotating the camera and mirror in endoscopes.     

First-principles calculations assisted thermodynamic assessment of the Pt–Ga–Ge ternary system

The Pt–Ga–Ge ternary system was thermodynamically assessed by the CALPHAD (CALculaton of PHAse Diagram) approach with help of first-principles calculations. Firstly, the formation enthalpies of the Pt–Ge and Pt–Ga compounds were calculated by the first-principles method. Subsequently, the Pt–Ge system was modeled and the Pt–Ga system was re-assessed. The solution phases, Liquid, Diamond_A4 (Ge) and Fcc_A1 (Pt), were modeled as substitutional solutions, of which the excess Gibbs energy was formulated with the Redlich–Kister polynomial. The binary intermetallics, Ga₇Pt₃, Ga₂Pt, Ga₃Pt₂, GaPt, Ga₃Pt₅, GaPt₂, Ge₂Pt, Ge₃Pt₂, GePt, Ge₂Pt₃ and GePt₂, were treated as stoichiometric compounds while GePt₃ was described with a two-sublattice model. Finally, based on the currently optimized Pt–Ga and Pt–Ge binary systems along with the already assessed Ga–Ge system, phase equilibria in the Pt–Ga–Ge ternary system were extrapolated. The isothermal sections at 473 K, 973 K and 1073 K of the ternary system were calculated, showing good agreement with the experimental data. In addition, the liquidus projection of the Pt–Ga–Ge ternary system was predicted using the obtained model parameters.