DC-link voltage control strategy for reducing capacitance and total harmonic distortion in single-phase grid-connected photovoltaic inverters

High-volume capacitance is required to buffer the power difference between the input and output ports in single-phase grid-connected photovoltaic inverters, which become an obstacle to high system efficiency and long device lifetime. Furthermore, total harmonic distortion becomes serious when the system runs into low power level. In this study, a comprehensive analysis is introduced for two-stage topology with the consideration of active power, DC-link (DCL) voltage, ripple and capacitance. This study proposed a comprehensive DCL voltage control strategy to minimise the DCL capacitance while maintaining a normal system operation. Furthermore, the proposed control strategy is flexible to be integrated with the pulse-skipping control that significantly improves the power quality at light power conditions. Since the proposed control strategy needs to vary DCL voltage, an active protection scheme is also introduced to prevent any voltage violation across the DCL. The proposed control strategy is evaluated by both simulation and experiments, whose results confirm the system effectiveness.

An analysis of five original compositions

The purpose of this thesis is to analyze in detail five original compositions, each written for the performance of these pieces on March 14, 2009 for a Master's recital. In order to maintain a certain level of musical continuity among these compositions, each was created in such a way as to possess similar musical characteristics of melodic and harmonic structure. These similarities are also reflected within the overall arrangement of each composition and use of instrumentation as well. The following pages will analyze each of these compositions in accordance with several important musical factors. These elements are form and chord analysis, melodic and harmonic content, and meter and rhythm. The author's original scores are included in the appendix.

Multipartite entanglement in harmonic oscillators subjected to dissipative quantum dynamics

Una detallada descripción de la dinámica de bajas energías del entrelazamiento multipartito es proporcionada para sistemas armónicos en una gran variedad de escenarios disipativos. Sin hacer ninguna aproximación central, esta descripción yace principalmente sobre un conjunto razonable de hipótesis acerca del entorno e interacción entorno-sistema, ambas consistente con un análisis lineal de la dinámica disipativa. En la primera parte se deriva un criterio de inseparabilidad capaz de detectar el entrelazamiento k-partito de una extensa clase de estados gausianos y no-gausianos en sistemas de variable continua. Este criterio se emplea para monitorizar la dinámica transitiva del entrelazamiento, mostrando que los estados no-gausianos pueden ser tan robustos frente a los efectos disipativos como los gausianos. Especial atención se dedicada a la dinámica estacionaria del entrelazamiento entre tres osciladores interaccionando con el mismo entorno o diferentes entornos a distintas temperaturas. Este estudio contribuye a dilucidar el papel de las correlaciones cuánticas en el comportamiento de la corrientes energéticas.

Petr Eben's oratorio Apologia Sokratus (1967) and ballet Curses and Blessings (1983): An interpretative analysis of the symbolism behind the text settings and musical style

The Czech composer Petr Eben (1927-2007) has written music in all genres except symphony, but he is highly recognized for his organ and choral compositions, which are his preferred genres. His vocal works include choral songs and vocal-instrumental works at a wide range of difficulty levels, from simple pedagogical songs to very advanced and technically challenging compositions. This study examines two of Eben‘s vocal-instrumental compositions. The oratorio Apologia Sokratus (1967) is a three-movement work; its libretto is based on Plato‘s Apology of Socrates. The ballet Curses and Blessings (1983) has a libretto compiled from numerous texts from the thirteenth to the twentieth centuries. The formal design of the ballet is unusual—a three-movement composition where the first is choral, the second is orchestral, and the third combines the previous two played simultaneously. Eben assembled the libretti for both compositions and they both address the contrasting sides of the human soul, evil and good, and the everlasting fight between them. This unity and contrast is the philosophical foundation for both compositions. The dissertation discusses the multileveled meanings behind the text settings and musical style of the oratorio and ballet in analyses focusing on the text, melodic and harmonic construction, and symbolism. Additional brief analyses of other vocal and vocal-instrumental compositions by Eben establish the ground for the examination of the oratorio and ballet and for understanding features of the composer‘s musical style. While the oratorio Apologia Sokratus was discussed in short articles in the 1970s, the ballet Curses and Blessings has never previously been addressed within Eben scholarship. The dissertation examines the significant features of Eben‘s music. His melodic style incorporates influences as diverse as Gregorian chant and folk tunes on the one hand, and modern vocal techniques such as Sprechgesang and vocal aleatoricism on the other. His harmonic language includes bitonality and polytonality, used to augment the tonal legacy of earlier times, together with elements of pitch collections and limited serial procedures as well as various secundal and quartal harmonic sonorities derived from them. His music features the vibrant rhythms of folk music, and incorporates other folk devices like ostinato, repetitive patterns, and improvisation.

Acoustic analysis of vocal dysphonia

Voice acoustic analysis is becoming more and more usefúl in diagnosis of voice disorders or laryngological pathologies. The facility to record a voice sigiial is an advantage over other invasive techniques. This paper presents the statistical analyzes ofa set of voice parameters like jitter, shimmer and HNR over a 4 groups of subjects vvith dysphonia, fünctional dysphonia, hyperfünctional dysphonia, and psychogenic dysphonia and a control group. No statistical signifícance differences over pathologic groups were found but clear tendencies can be seen between pathologic and control group. The tendencies indicates this parameters as a good features to be used in an intelligent diagnosis system, moreover the jitter and shimmer parameters measured over different tones and vowels.

An in-depth analysis of original compositions

The purpose of this thesis is two-fold. It presents six original pieces composed and arranged by the author, and it provides a thorough analysis of each. The compositions draw from many different musical genres: contemporary jazz, swing, funk, fusion, soul, neo-soul, and rhythm and blues. The applications of melodic, harmonic, and rhythmic techniques derived from these genres can be found in these original compositions. These compositions are inspired by -- and attempt to narrate --life experiences. Parallels between life and music are drawn and explained. By way of introduction, some information is given regarding the ensemble that first performed these original compositions. The ensemble comprised trumpet, tenor saxophone, keyboards, piano, electric bass, upright acoustic bass, drums, and percussion.

Raman microscopy of formamide-intercalated kaolinites treated by controlled-rate thermal analysis technology

Raman spectroscopy of formamide-intercalated kaolinites treated using controlled-rate thermal analysis technology (CRTA), allowing the separation of adsorbed formamide from intercalated formamide in formamide-intercalated kaolinites, is reported. The Raman spectra of the CRTA-treated formamide-intercalated kaolinites are significantly different from those of the intercalated kaolinites, which display a combination of both intercalated and adsorbed formamide. An intense band is observed at 3629 cm-1, attributed to the inner surface hydroxyls hydrogen bonded to the formamide. Broad bands are observed at 3600 and 3639 cm-1, assigned to the inner surface hydroxyls, which are hydrogen bonded to the adsorbed water molecules. The hydroxyl-stretching band of the inner hydroxyl is observed at 3621 cm-1 in the Raman spectra of the CRTA-treated formamide-intercalated kaolinites. The results of thermal analysis show that the amount of intercalated formamide between the kaolinite layers is independent of the presence of water. Significant differences are observed in the CO stretching region between the adsorbed and intercalated formamide.

Detailed analysis of a conservative difference approximation for the time fractional diffusion equation

Diffusion equations that use time fractional derivatives are attractive because they describe a wealth of problems involving non-Markovian Random walks. The time fractional diffusion equation (TFDE) is obtained from the standard diffusion equation by replacing the first-order time derivative with a fractional derivative of order α ∈ (0, 1). Developing numerical methods for solving fractional partial differential equations is a new research field and the theoretical analysis of the numerical methods associated with them is not fully developed. In this paper an explicit conservative difference approximation (ECDA) for TFDE is proposed. We give a detailed analysis for this ECDA and generate discrete models of random walk suitable for simulating random variables whose spatial probability density evolves in time according to this fractional diffusion equation. The stability and convergence of the ECDA for TFDE in a bounded domain are discussed. Finally, some numerical examples are presented to show the application of the present technique.

Determination of preventive maintenance lead time using hybrid analysis

The time for conducting Preventive Maintenance (PM) on an asset is often determined using a predefined alarm limit based on trends of a hazard function. In this paper, the authors propose using both hazard and reliability functions to improve the accuracy of the prediction particularly when the failure characteristic of the asset whole life is modelled using different failure distributions for the different stages of the life of the asset. The proposed method is validated using simulations and case studies.