Continuous harmonic analysis and power quality measurements in three-phase systems

A virtual instrument, named Power Quality Meter, is presented for (a) measuring power consumption and harmonics in three-phase systems, under non-sinusoidal and imbalance conditions (b) detecting, classifying and organizes power disturbance events. Measurement of the power consumption follows the formulation proposed by the members of the IEEE Working Group on Nonsinusoidal Situations (1996). So, definitions are based on the analysis of functions in the frequency domain, separating the fundamental terms from the harmonic terms of the Fourier series. The virtual instrument has been developed too for monitoring and measuring power disturbances, which are automatically classified and organized in a database while they are being recorded. Software tools use the database structure to present summaries of power disturbances and locate an event by severity or time of occurrence. Records of actual measurements are included to demonstrate the versatility of the instrument

Instantaneous current vectors in polyphase systems: two compensation concepts

6 páginas, 9 figuras, 24 referencias.-- Trabajo presentado al Modern Electric Power Systems (MEPS) International Symposium, celebrado del 20-22 de septiembre 2010, en Wroclaw, Polonia.According to the target of minimal line losses and a power factor equal to one, the present work studies two concepts of instantaneous compensation of nonactive current which are generally applied to polyphase systems. The analysis is defined both on the basis of the instantaneous value concept, for arbitrary voltage and current waveforms, and on the basis of the average value concept, for steady-state and periodic conditions. Results of using these concepts for instantaneous compensation are compared by simulation.Peer reviewe

Magnetic exchange interaction in a pair of orbitally degenerate ions: Magnetic anisotropy of [Ti2Cl9]−3

The theory of the kinetic exchange in a pair of orbitally degenerate ions developed by the authors [J. Phys. Chem. A 102, 200 (1998)] is applied to the case of face-shared bioctahedral dimer (overall D3h-symmetry). The effective kinetic exchange Hamiltonian is found for a 2T2–2T2 system taking into account all relevant transfer pathways and charge-transfer crystal field states. The influence of different transfer integrals involved in the kinetic exchange on the energy pattern and magnetic properties of the system is examined. The role of other related interactions (trigonal crystal field, spin–orbit coupling) is also discussed in detail. Using the pseudoangular momentum representation and the technique of the irreducible tensor operators of R3-group we give a general outlook on the nontrivial symmetry properties of the effective Hamiltonian for the D3h-pair, and on the magnetic anisotropy arising from the orbital interactions specific for the case of orbital degeneracy. The magnetic properties of the binuclear unit [Ti2Cl9]−3 in Cs3Ti2Cl9 are discussed with a special emphasis on the magnetic anisotropy experimentally observed in this system. The existing exchange models for [Ti2Cl9]−3 and the concept of the effective Hamiltonian are discussed in the context of the present [email protected] ; [email protected] ; [email protected] ; [email protected]

Analizadores de red de bajo coste

El uso masivo de dispositivos electrónicos, tanto en entornos domésticos como industriales, tiene un impacto directo e inmediato en la creciente y compleja red de distribución eléctrica a la que se conectan. De aquí la necesidad de analizar la calidad de la señal eléctrica y su energía asociada en la propia red e instalaciones afectadas. Por otra parte, la evolución exponencial de microcontroladores y micro PC´S y su aplicación al procesado de señales, convierte a estos dispositivos en candidatos excepcionales para cubrir la mencionada necesidad del análisis de la calidad eléctrica. Esta es justamente la propuesta que se hace en este trabajo. La detección de las perturbaciones eléctricas de mayor incidencia en la calidad de la señal de red se puede realizar de diferentes formas. En este caso, se propone el uso de una potente herramienta matemática como es la Transformada Wavelet (TW), con una contrastada aplicabilidad en este campo. Su traducción a nivel de programación mediante un complejo algoritmo es implementada en dispositivos de bajo coste, particularmente en Arduino y Raspberry Pi. A partir de este algoritmo es posible la detección, análisis y clasificación de distintas perturbaciones eléctricas de forma más intuitiva. Se ha diseñado un sistema capaz de adquirir y analizar la señal de la tensión eléctrica y monitorizar dichos resultados, demostrando la aptitud de estos sistemas de bajo coste para dicho análisis.The massive use of electronic devices, both in domestic and industrial environments, has a direct and immediate impact on the electrical network in which they are connected. This fact generates the need for a power quality analysis in the electrical distribution network and affected installations. On the other hand, the exponential evolution of microcontrollers and micro PC'S and their application to signal processing, makes these devices exceptional candidates to cover the aforementioned power quality analysis. This is precisely the proposal made in this work. The detection of electrical disturbances with greater incidence in power quality can be made in different ways. In this case, the use of a powerful mathematical tool such as the Wavelet Transform (WT), with a proven applicability in this field, is proposed. Its translation at the programming level through a complex algorithm is implemented in low cost devices, particularly in Arduino and Raspberry Pi. From this algorithm it is possible to detect, analyze and classify different electrical disturbances in a more intuitive way. A system capable of acquiring and analyzing the voltage signal, as well as monitoring the results, has been designed, showing the capacity of these low cost devices for such analysis.Plan Propio de la Universidad de Sevilla Proyecto: 2017/0000096

Short-course thrombolysis as the first line of therapy for cardiac valve thrombosis

AbstractObjective: To retrospectively evaluate the clinical and echocardiographic criteria of thrombolytic therapy for mechanical heart valve thrombosis. Methods: Nineteen consecutive patients with 22 instances of prosthetic heart valve thrombosis (14 mitral, 2 aortic, 3 tricuspid, and 3 pulmonary) were treated with short-course thrombolytic therapy as first option of treatment in absence of contraindications. The thrombolytic therapy protocol consisted of streptokinase (1,500,000 IU in 90 minutes) (n = 18) in one (n = 7) or two (n = 11) cycles or recombinant tissue-type plasminogen activator (100 mg in 90 minutes) (n = 4). Results: Overall success was seen in 82%, immediate complete success in 59%, and partial success in 23%. Six patients without total response to thrombolytic therapy underwent surgery, and pannus was observed in 83%. Six patients showed complications: allergy, stroke, transient ischemic attack, coronary embolism, minor bleeding, and one death. At diagnosis, 10 patients evidenced atrial thrombus by transesophageal echocardiography, 3 of whom experienced peripheral embolism during thrombolysis. Four episodes of rethrombosis were observed (16%). The survivorship was 84% with a mean follow-up of 42.6 months. Conclusions: A short-course of thrombolytic therapy may be considered first-line therapy for prosthetic heart valve thrombosis. The risk of peripheral embolism may be evaluated for the presence of atrial thrombus by transesophageal echocardiography at diagnosis. (J Thorac Cardiobasc Surg 1998;115:780-4

Vacuum template synthesis of multifunctional nanotubes with tailored nanostructured walls

A three-step vacuum procedure for the fabrication of vertical TiO2 and ZnO nanotubes with three dimensional walls is presented. The method combines physical vapor deposition of small-molecules, plasma enhanced chemical vapor deposition of inorganic functional thin films and layers and a postannealing process in vacuum in order to remove the organic template. As a result, an ample variety of inorganic nanotubes are made with tunable length, hole dimensions and shapes and tailored wall composition, microstructure, porosity and structure. The fabrication of multishell nanotubes combining different semiconducting oxides and metal nanoparticles is as well explored. This method provides a feasible and reproducible route for the fabrication of high density arrays of vertically alligned nanotubes on processable substrates. The emptying mechanism and microstructure of the nanotubes have been elucidated through SEM, STEM, HAADF-STEM tomography and energy dispersive X-ray spectroscopy. In this article, as a proof of concept, it is presented the straightforward integration of ZnO nanotubes as photoanode in a photovoltaic cell and as a photonic oxygen gas sensorPeer reviewe

PTEN Mediates the Antioxidant Effect of Resveratrol at Nutritionally Relevant Concentrations

Introduction. Antioxidant properties of resveratrol have been intensively studied for the last years, both in vivo and in vitro. Its bioavailability after an oral dose is very low and therefore it is very important to make sure that plasma concentrations of free resveratrol are sufficient enough to be active as antioxidant. Aims. In the present study, using nutritionally relevant concentrations of resveratrol, we aim to confirm its antioxidant capacity on reducing peroxide levels and look for the molecular pathway involved in this antioxidant effect. Methods. We used mammary gland tumor cells (MCF-7), which were pretreated with different concentrations of resveratrol for 48 h, and/or a PTEN inhibitor (bpV: bipy). Hydrogen peroxide levels were determined by fluorimetry, PTEN levels and Akt phosphorylation by Western Blotting, and mRNA expression of antioxidant genes by real-time reverse transcriptase-polymerase chain reaction (RT-PCR). Results. Resveratrol treatment for 48 h lowered peroxide levels in MCF-7, even at low nutritional concentrations (1 nM). This effect was mediated by the activation of PTEN/Akt pathway, which resulted in an upregulation of catalase and MnSOD mRNA levels. Conclusion. Resveratrol acts as an antioxidant at nutritionally relevant concentrations by inducing the expression of antioxidant enzymes, through a mechanism involving PTEN/Akt signaling pathway

Rhodamine 6G and 800 intermolecular heteroaggregates embedded in PMMA for near-infrared wavelength shifting

The opto-electronic properties of small-molecules and functional dyes usually differ when incorporated into solid matrices with respect to their isolated form due to an aggregation phenomenon that alters their optical and fluorescent properties. These spectroscopic modifications are studied in the framework of the exciton theory of aggregates, which has been extensively applied in the literature for the study of molecular aggregates of the same type of molecules (homoaggregation). Despite the demonstrated potential of the control of the heteroaggregation process (aggregation of different types of molecules), most of the reported works are devoted to intramolecular aggregates, complex molecules formed by several chromophores attached by organic linkers. The intramolecular aggregates are specifically designed to hold a certain molecular structure that, on the basis of the exciton theory, modifies their optical and fluorescent properties with respect to the isolated chromophores that form the molecule. The present article describes in detail the incorporation of Rhodamine 6G (Rh6G) and 800 (Rh800) into polymeric matrices of poly-(methyl methacrylate), PMMA. The simultaneous incorporation of both dyes results in an enhanced fluorescent emission in the near-infrared (NIR), originating from the formation of ground-state Rh6G–Rh800 intermolecular heteroaggregates. The systematic control of the concentration of both rhodamines provides a model system for the elucidation of the heteroaggregate formation. The efficient energy transfer between Rh6G and Rh800 molecules can be used as wavelength shifters to convert effectively the light from visible to NIR, a very convenient wavelength range for many practical applications which make use of inexpensive commercial detectors and systems