Split-then-Combine Method for out-of-sample Combinations of Forecasts

Relative forecast performance of forecast units may periodically evolve over time. Therefore, it is desirable to take into account their forecast periodicity when forming forecast combinations. When dealing with small samples and small number of models, using panels is an efficient way of pulling out the additional information provided by that periodicity in the data. We capture this periodic information with different weights at different periods that we then keep in the out-of-sample combination. As in the simple average, we do not estimate weights, but instead compute them from panels of forecasts taken as given data. Empirical and bootstrap exercises illustrate the superiority of this method over fixed weight scheme

Soluciones ARMA-ER a modelos monetarios con expectivas racionales

Tesis doctoral inédita. Universidad Autónoma de Madrid. Facultad de Ciencias Económicas y Empresariales, Deapartamento de Análisis Económico, 198

Stand-alone hybrid power plant based on SiC solar PV and wind inverters with smart spinning reserve management

Stand-alone hybrid power plants based on renewable energy sources are becoming a more and more interesting alternative. However, their management is a complex task because there are many variables, requirements and restrictions as well as a wide variety of possible scenarios. Though a proper sizing of the power plant is necessary to obtain a competitive cost of the energy, smart management is key to guarantee the power supply at a minimum cost. In this work, a novel hybrid power plant control strategy is designed, implemented and simulated under a wide variety of scenarios. Thereby, the proposed control algorithm aims to achieve maximum integration of renewable energy, reducing the usage of non-renewable generators as much as possible and guaranteeing the stability of the microgrid. Different scenarios and case studies have been analyzed by dynamic simulation to verify the proper operation of the power plant controller. The main novelties of this work are: (i) the stand-alone hybrid power plant management regarding a battery energy storage system as a part of the spinning reserve, (ii) the characterization of the largest loads as non-priority loads, (iii) the minimization of the needed spinning reserve and fuel consumption from diesel generators

Core losses analysis of the LCL filter inductor for SiC-based inverter

The ability of SiC devices to switch at high speed allows increasing significantly the power density in both converters and passive components, reducing their required size. To mitigate harmonic injection form inverters into the grid, in order to comply with power quality standards, an accurate filter design is required. Given its excellent performance, an LCL filter is the configuration most suitable in grid-connected power converters. Several parameters must be considered when designing an effective LCL filter, and the inverter-side inductor assumes a special importance because of its relevance to suppress high frequency harmonic content at the inverter side. One of the most relevant issues to be considered in the process of designing the LCL filter is the evaluation of core losses in the inverter-side inductor, which will determine the final temperature of the inductor. This paper analyses the core losses of the inverter-side inductor of an LCL filter. The proposed method is based on the computation of the current harmonics generated by the inverter and on Steinmetz’s empirical equation. As a result, core losses calculated taking into account several carrier and sideband harmonics show good agreement with the experimental values. When current harmonics are estimated by simulation, as it is done in the proposed design procedure, results are less accurate, but precise enough for a design procedure

An anti-islanding protection based on RoCoF compliant with ENTSO-E and IEC 62116

In case of unintentional islanding, distributed generation units must be able to detect it and disconnect from the grid in less than 2 seconds. In this work, a Rate of Change of Frequency (RoCoF) method has been developed for islanding detection. Since these algorithms are conditioned by the requirements of grid codes, ENTSO-E network code and IEC 62116 have been taken into account. The RoCoF anti-islanding algorithm has been developed in MATLAB-Simulink and implemented through rapid prototyping techniques in an FPGA ALTERA Cyclone V. To check the proposed protection algorithm, simulation tests have been carried out. Finally, the RoCoF anti-islanding protection has been validated using FPGA in the loop and experimentally in a real 20-kW inverter. © 2022, European Association for the Development of Renewable Energy, Environment and Power Quality (EA4EPQ). All rights reserved

PCR-DGGE assessment of the bacterial diversity of breast milk in women with lactational infectious mastitis

<p>Abstract</p> <p>Background</p> <p>Infectious mastitis is a common condition during lactation and in fact, represents one of the main causes leading to a precocious weaning. The number of studies dealing with lactational mastitis is low and, up to now, the etiological diagnosis is frequently made on the basis of unspecific clinical signs. The aim of this study was to investigate the microbial diversity of breast milk in 20 women with lactational mastitis employing culture-dependent and culture-independent (PCR-DGGE) approaches.</p> <p>Methods</p> <p>Breast milk samples were cultured in different media to investigate the presence of bacteria and/or yeasts, and a total of 149 representative isolates were identified to the species level by 16S rRNA gene PCR sequencing. The microorganisms recovered were compared with those found by PCR-DGGE analysis. To identify the DGGE profiles two reference markers of different microbial species were constructed. Sequence analysis of unknown bands was also performed.</p> <p>Results</p> <p>Staphylococci were the dominant bacterial group and <it>Staphylococcus epidermidis </it>was the dominant species. In a lower number of samples, other bacteria (mainly streptococci and a few gram-negative species) were also identified. Globally, PCR-DGGE results showed a good correlation with those obtained by culture-based methods. However, although DNA bands corresponding to different lactic acid bacteria were detected, such bacteria could not be isolated from the milk samples.</p> <p>Conclusion</p> <p>Staphylococci seem to be the main etiological agents of human lactational mastitis. The combined use of culture and molecular techniques allowed a better characterization of the bacterial diversity in milk from women suffering from infectious mastitis. Our results suggest that this condition could be the result of a disbiotic process where some of the bacterial species usually present in human milk outgrow (staphylococci) while others disappear (lactobacilli or lactococci).</p

A new test for random number generators: Schwinger-Dyson equations for the Ising model

We use a set of Schwinger-Dyson equations for the Ising Model to check several random number generators. For the model in two and three dimensions, it is shown that the equations are sensitive tests of bias originated by the random numbers. The method is almost costless in computer time when added to any simulation.Comment: 6 pages, 3 figure

Turnos de 7 horas versus 12 horas en enfermería intensiva: vivir a contratiempo

Resumen Los turnos de trabajo tienen repercusión sobre el bienestar de los profesionales sanitarios influyendo en su calidad de vida. El objetivo principal de este estudio es describir las consecuencias que tiene el turno de trabajo diurno de 12 h respecto al de 7 h en los profesionales de enfermería que trabajan en Unidades de Cuidados Intensivos. Se trata así de un estudio descriptivo transversal en 2 hospitales de tercer nivel de Barcelona: Hospital Clínico y Hospital Vall d"Hebron (turnos de 7 h y 12 h respectivamente). La recogida de datos se ha realizado mediante cuestionario ad hoc de 29 preguntas cerradas, anónimo y autoadministrado, basado en 2 escalas: Standard Shiftwork Index y Shiftwork locus of control. Dichos datos fueron procesados a través del programa SPSS V.18.0. De las 85 encuestas realizadas 52 fueron válidas: 22 en el Hospital Clínico de Barcelona y 30 en el Hospital Vall d"Hebron. Cabe destacar que los profesionales encuestados que trabajan en turno de 12 h expresan niveles superiores de conciliación laboral y personal, concretamente en tiempo de ocio a disfrutar (× 2: 10,635; p = 0,031) y tiempo de dedicación familia-amigos, así como niveles más bajos de percepción de fatiga. No se han encontrado diferencias entre el tipo de turno y facilidad de desarrollo del trabajo profesional, a pesar de que el turno de 12 h presenta niveles más altos

Validation of miR-1228-3p as Housekeeping for MicroRNA Analysis in Liquid Biopsies from Colorectal Cancer Patients

BACKGROUND: Circulating microRNA (miRNA) analysis is a growing research field. However, it usually requires an endogenous control or housekeeping (HK) in order to normalize expression of specific miRNAs throughout different samples. Unfortunately, no adequate HK for circulating miRNA analysis is still known in the colorectal cancer (CRC) context whereas several have been suggested. Hence, our aims were to validate the previously suggested miR-1228-3p as HK for CRC studies, to compare its suitability with the widely used miR-16-5p, and to evaluate the influence of hemolysis on both miRNAs. METHODS: We analyzed by quantitative reverse-transcription polymerase chain reaction (qRT-PCR) the expression of miR-1228-3p, miR-16-5p and the spike-in cel-miR-39 in a set of 297 plasmas (92 CRC, 101 advanced adenomas -AA-, and 100 controls) and 213 serum samples (59 CRC, 74 AA and 80 controls). We also analyzed both miRNAs depending on the hemolysis degree in 7 plasmas and 31 serums. RESULTS: Levels of miR-1228-3p and miR-16-5p did not show significant differences between groups although miR-16-5p exhibited more variability in plasma and serum samples. Importantly, the combination of cel-miR-39 and miR-1228-3p was the most stable one. Moreover, we observed that miR-16-5p was significantly influenced by hemolysis in contrast with miR-1228-3p that exhibited no correlation with this confounding factor in both biofluids. CONCLUSION: MiR-1228-3p has been validated as an adequate endogenous control for circulating miRNA analysis in CRC and AA liquid biopsies