Wavemoth -- Fast spherical harmonic transforms by butterfly matrix compression

We present Wavemoth, an experimental open source code for computing scalar spherical harmonic transforms (SHTs). Such transforms are ubiquitous in astronomical data analysis. Our code performs substantially better than existing publicly available codes due to improvements on two fronts. First, the computational core is made more efficient by using small amounts of precomputed data, as well as paying attention to CPU instruction pipelining and cache usage. Second, Wavemoth makes use of a fast and numerically stable algorithm based on compressing a set of linear operators in a precomputation step. The resulting SHT scales as O(L^2 (log L)^2) for the resolution range of practical interest, where L denotes the spherical harmonic truncation degree. For low and medium-range resolutions, Wavemoth tends to be twice as fast as libpsht, which is the current state of the art implementation for the HEALPix grid. At the resolution of the Planck experiment, L ~ 4000, Wavemoth is between three and six times faster than libpsht, depending on the computer architecture and the required precision. Due to the experimental nature of the project, only spherical harmonic synthesis is currently supported, although adding support or spherical harmonic analysis should be trivial.Comment: 13 pages, 6 figures, accepted by ApJ

A study an effect of harmonic in computer laboratory of UiTM Pulau Pinang / Muhammad Aizat Nasir

The research of this project is to study an effect of harmonic in computer laboratory at UiTM Pulau Pinang. Basically, the harmonic distortion either current or voltage is known as the changes of amplitude in the waveform of voltage source from the ideal sinusoidal waveform. This is because of non-linear loads such as computers generate the harmonic to the supply. The levels of harmonic distortion at the DB of computer laboratory in UiTM Pulau Pinang will be measured by Fluke 1750 power equipment. An analysis will be made based on harmonic data that was taken. The purpose is to develop analytical method in designing the passive filter that will mitigate the harmonic currents caused by computer loads. For this project, MATLAB /SIMULINK was used to design the proposed model of passive filter circuit to mitigate the harmonic. The simulation circuit of equivalent SMPS for the computer laboratory have 3 different phase which is phase A, phase B and phase C. Simulation results from the proposed circuit model will show the difference result of harmonic levels which have higher THDI before installation of passive filter while after passive filter installation, the THDI levels was reduced

Chemical applications of escience to interfacial spectroscopy

This report is a summary of works carried out by the author between October 2003 and September 2004, in the first year of his PhD studie

Teaching rule‐based algorithmic composition: the PWGL library cluster rules

This paper presents software suitable for undergraduate students to implement computer programs that compose music. The software offers a low floor (students easily get started) but also a high ceiling (complex compositional theories can be modelled). Our students are particularly interested in tonal music: such aesthetic preferences are supported, without stylistically restricting users of the software. We use a rule‐based approach (constraint programming) to allow for great flexibility. Our software Cluster Rules implements a collection of compositional rules on rhythm, harmony, melody, and counterpoint for the new music constraint system Cluster Engine by Örjan Sandred. The software offers a low floor by observing several guidelines. The programming environment uses visual programming (Cluster Rules and Cluster Engine extend the algorithmic composition system PWGL). Further, music theory definitions follow a template, so students can learn from examples how to create their own definitions. Finally, students are offered a collection of predefined rules, which they can freely combine in their own definitions. Music Technology students, including students without any prior computer programming experience, have successfully used the software. Students used the musical results of their computer programs to create original compositions. The software is also interesting for postgraduate students, composers and researchers. Complex polyphonic constraint problems are supported (high ceiling). Users can freely define their own rules and combine them with predefined rules. Also, Cluster Engine’s efficient search algorithm makes advanced problems solvable in practice

New Results on Massive 3-Loop Wilson Coefficients in Deep-Inelastic Scattering

We present recent results on newly calculated 2- and 3-loop contributions to the heavy quark parts of the structure functions in deep-inelastic scattering due to charm and bottom.Comment: Contribution to the Proc. of Loops and Legs 2016, PoS, in prin

Evaluation of harmonic generating properties of schottky barrier diodes

Low noise figure communication receivers require more efficient frequency converters. Frequency conversion and multiplication processes cannot take place without the existence of harmonic sources in the system and the inherent property of a nonlinear element is to generate harmonics. Such nonlinearity, in general, may be provided by semiconductor diodes. This research project deals with the theoretical analysis as well as the experimental verifications of the harmonic generating properties of a nonlinear resistive device, i.e. Schottky-barrier diode. Laboratory measurements associated with the equivalent circuit representation of hot-carrier diodes show that their i-v characteristics can be accurately described by the modified exponential law, i = I(_s) [exp α (V–iR(_T)-1, over a wide range of the applied voltage V. Using this equation, a procedure is developed for the harmonic analysis of the resistive diode and calculation of any of a finite number of harmonic currents having a single frequency sinusoidal voltage V(_p) cos w(_p)t as the drive. The amplitudes of the harmonic currents are expressed as a power series in αR(_T)I(_S)) exp (αR(_T)I(_S)) where the coefficients of the power series are represented through the modified Bessel function of the k(^th) of order n. The integers k and n represent the power of the series and the harmonic number respectively, e.g. i(_n) α I(_n) (k α v(_p)) [αR(_T)I(_S) exp (αR(_T)I(_S))](^k). The power series solutions for the exponential diodes do not normally converge quickly enough to be of practical value for numerical evaluations. A different approach is proposed which is suitable for numerical evaluations of harmonic amplitudes. The results are compared with experimental data on twelve diodes, four in each of the three groups of different types. A good agreement, within the measuring instruments tolerances, was found between the calculated and the experimental results. Finally, it is believed that such studies were justified as the new method of approach presented here evaluates fully the capabilities of these diodes in practice. Many analyses published over the years have tended to introduce severe approximations which were only valid in practice over limited ranges of operation. In this project, attempts were made over almost two years to obtain mathematical solutions for the exponential diode law which are useful in practice and which give accurate prediction of harmonic amplitudes and spectrum. Various methods were employed to achieve the necessary convergence of the infinite series solutions. This involved a good understanding of the mathematical methods employed and computer programming. During the same period at every stage experimental verifications were being attempted, many times unsuccessfully, which finally led to a good agreement between the theory and experimental results as shown in this thesis