2,269 research outputs found
A Comparative Study of Physicochemical, Dielectric and Thermal Properties of Pressboard Insulation Impregnated with Natural Ester and Mineral Oil
No full textNatural ester is considered to be a substitute of mineral oil in the future. To apply natural ester in large transformers safely, natural ester impregnated solid insulation should be proved to have comparable dielectric strength and thermal stability to mineral oil impregnated solid insulation. This paper mainly focuses on a comparative study of physicochemical, ac breakdown strength and thermal stability behavior of BIOTEMP natural ester/pressboard insulation and Karamay 25# naphthenic mineral oil/pressboard insulation after long term thermal ageing. The physicochemical and dielectric parameters including moisture, acids and the ac breakdown strength of these two oil/pressboard insulation systems at different ageing status were compared. The permittivity and ac breakdown strength of these two oil/pressboard insulation systems at different temperatures were also investigated. And a comparative result of the thermal stability behavior of these two oil/pressboard insulation systems with different ageing status was provided at last. Results show that though natural ester has higher absolute humidity and acidity during the long ageing period, the lower relative humidity of natural ester helps to keep its ac breakdown strength higher than mineral oil. The pressboard aged in natural ester also has higher ac breakdown strength than that aged in mineral oil. The lower relative permittivity ratio of natural ester impregnated paper to natural ester is beneficial to its dielectric strength. Using natural ester in transformer, the resistance to thermal decomposition of the oil/pressboard insulation system could be also effectively improved
<i>No se sabe</i>: entrevista a Nilda Ester Radman
No full textEntrevista a la médica veterinaria y bacterióloga clínica industrial Nilda Ester Radman, profesora titular de Parasitología Comparada en la Facultad de Ciencias Veterinarias de nuestra universidad y estudiosa de las enfermedades zoonóticas.Al hacer clic en el enlace que figura en "Documentos relacionados", pueden accederse a todos los trabajos de Nilda Ester Radman presentes en el repositorio.Radio Universidad Nacional de La Plat
Quantitative Analysis Ageing Status of Natural Ester-paper Insulation and Mineral Oil-paper Insulation by Polarization/Depolarization Current
No full textPolarization and Depolarization Current (PDC) technique is an effective tool to assess the condition of oil-paper insulation system in power transformers. So far the PDC behaviors of mineral oil-paper insulation have been widely investigated. However, with the increasing number of transformer choosing natural ester as its insulation oil, it is important to investigate the PDC characteristics of natural ester-paper insulation to see whether the PDC technique can also be used to assess the condition of new insulation system using natural ester in transformers accurately. In this research, natural esterpaper insulation sample and mineral oil-paper insulation sample were subjected to thermally accelerated ageing experiment at 110 °C for 120 days. The PDC characteristics of natural ester-paper insulation sample and mineral oil-paper insulation sample were compared over the ageing process. A new method for assessing the ageing condition of the oil-paper insulation in terms of the depolarization charge quantity was proposed. Results show that the polarization/depolarization current of natural ester-paper insulation sample is higher than that of mineral oil-paper insulation sample with the same ageing intervals. The depolarization charge quantity of both kinds of oil-paper insulation sample is very sensitive to their ageing conditions. There is an exponential relation between the stable depolarization charge quantity of both kinds of oil-paper insulation sample and the degree of polymerization (DP) of paper. The depolarization charge quantity can be used to predict the ageing condition of oil-paper insulation providing the measurement temperature is kept the same
Exploring ICA for time series decomposition
No full textIn this paper, we apply independent component analysis (ICA) for prediction and signal extraction in multivariate time series data. We compare the performance of three different ICA procedures, JADE, SOBI, and FOTBI that estimate the components exploiting either the non-Gaussianity, or the temporal structure of the data, or combining both, non-Gaussianity as well as temporal dependence. Some Monte Carlo simulation experiments are carried out to investigate the performance of these algorithms in order to extract components such as trend, cycle, and seasonal components. Moreover, we empirically test the performance of those three ICA procedures on capturing the dynamic relationships among the industrial production index (IPI) time series of four European countries. We also compare the accuracy of the IPI time series forecasts using a few JADE, SOBI, and FOTBI components, at different time horizons. According to the results, FOTBI seems to be a good starting point for automatic time series signal extraction procedures, and it also provides quite accurate forecasts for the IPIs.ICA, Signal extraction, Multivariate time series, Forecasting
On the Feasibility of Interoperable Schemes in Hand Biometrics
No full textPersonal recognition through hand-based biometrics has attracted the interest of many researchers in the last twenty years. A significant number of proposals based on different procedures and acquisition devices have been published in the literature. However, comparisons between devices and their interoperability have not been thoroughly studied. This paper tries to fill this gap by proposing procedures to improve the interoperability among different hand biometric schemes. The experiments were conducted on a database made up of 8,320 hand images acquired from six different hand biometric schemes, including a flat scanner, webcams at different wavelengths, high quality cameras, and contactless devices. Acquisitions on both sides of the hand were included. Our experiment includes four feature extraction methods which determine the best performance among the different scenarios for two of the most popular hand biometrics: hand shape and palm print. We propose smoothing techniques at the image and feature levels to reduce interdevice variability. Results suggest that comparative hand shape offers better performance in terms of interoperability than palm prints, but palm prints can be more effective when using similar sensors
El dia d'avui del fons musical de l'Arxiu de la Catedral de Lleida
No full textDespués de una breve introducción histórica, Ester G. Llop, también del equipo de los profesores Gregori y Rifé, nos ofrece los nuevos planteamientos para la descripción y catalogación del fondo musical de la catedral de Lleida. Divide este fondo en tres grupos: pergaminos, impresos y manuscritos. Subraya que gran parte del fondo de manuscritos es obra de Magí Pontí i Ferrer, nacido en Manresa en 1815 y formado en el monasterio de Montserrat; ejerció como primer organista y maestro de capilla durante 48 años en la catedral de Lleida.Ester Garcia Llop, également membre de l'équipe des professeurs Gregori et Rifé, nous offre une brève introduction historique, suivie des nouvelles méthodes d'approche appliquées à la description et au catalogage du fonds musical de la cathédrale de Lérida. Elle divise ce fonds en trois groupes : parchemins, imprimés et manuscrits. Ester Garcia Llop indique également que l'on doit la plupart du fonds de manuscrits à Magí Pontí i Ferrer. Ce dernier naquit à Manresa en 1815 et fut formé dans le monastère de Montserrat, puis remplit les fonctions de premier organiste et de maître de chapelle durant 48 ans dans la cathédrale de Lérida.After a brief historical introduction, Ester Garcia Llop, also a member of the team under Professors Gregori and Rifé, offers new thoughts on the description and compilation of the musical fund of the Cathedral of Lleida. This fund is divided into three groups: parchment, printed and manuscripts. It emphasizes that a large part of the fund of manuscripts is the work of Magí Pontí i Ferrer, born in Manresa in 1815 and educated at the monastery of Montserrat. He was the first organist and the chapel master for 48 years at the Cathedral of Lleida.Nach einer kurzen geschichtlichen Einführung beschreibt Ester Garcia Llop, ebenfalls Mitglied des Teams der Professoren Gregori und Rifé die neuen Gedanken zur Beschreibung und Katalogisierung der Musikalischen Grundlagen der Kathedrale von Lleida. Sie teilt diese Grundlagen in drei Gruppen ein: Pergamente, Drucke und Manuskripte. Sie weist vor allem auf die Tatsache hin, dass ein Grossteil Werke von Magí Pontí i Ferrer, geboren in Manresa im Jahr 1815, ausgebildet im Kloster von Montserrat, sind; er war 48 Jahre lang erster Organist und Kapellmeister der Kathedrale von Lleida
A multivariate generalized independent factor GARCH model with an application to financial stock returns
No full textWe propose a new multivariate factor GARCH model, the GICA-GARCH model , where the data are assumed to be generated by a set of independent components (ICs). This model applies independent component analysis (ICA) to search the conditionally heteroskedastic latent factors. We will use two ICA approaches to estimate the ICs. The first one estimates the components maximizing their non-gaussianity, and the second one exploits the temporal structure of the data. After estimating the ICs, we fit an univariate GARCH model to the volatility of each IC. Thus, the GICA-GARCH reduces the complexity to estimate a multivariate GARCH model by transforming it into a small number of univariate volatility models. We report some simulation experiments to show the ability of ICA to discover leading factors in a multivariate vector of financial data. An empirical application to the Madrid stock market will be presented, where we compare the forecasting accuracy of the GICA-GARCH model versus the orthogonal GARCH one.ICA, Multivariate GARCH, Factor models, Forecasting volatility
A multivariate generalized independent factor GARCH model with an application to financial stock returns
No full textWe propose a new multivariate factor GARCH model, the GICA-GARCH model ,
where the data are assumed to be generated by a set of independent components (ICs).
This model applies independent component analysis (ICA) to search the conditionally
heteroskedastic latent factors. We will use two ICA approaches to estimate the ICs. The
first one estimates the components maximizing their non-gaussianity, and the second
one exploits the temporal structure of the data. After estimating the ICs, we fit an
univariate GARCH model to the volatility of each IC. Thus, the GICA-GARCH reduces
the complexity to estimate a multivariate GARCH model by transforming it into a small
number of univariate volatility models. We report some simulation experiments to show
the ability of ICA to discover leading factors in a multivariate vector of financial data.
An empirical application to the Madrid stock market will be presented, where we
compare the forecasting accuracy of the GICA-GARCH model versus the orthogonal
GARCH one
Ester Formation
No full textThe present invention is in the field of a process for producing an ester, such as a biobased ester, from an aqueous biomass comprising solution, batch wise or continuously, wherein use of raw material is limited and if possible re-used. The present invention is in the field of green technology.BT/BiotechnologyApplied Science
El dia d'avui del fons musical de l'Arxiu de la Catedral de Lleida
No full textDespués de una breve introducción histórica, Ester G. Llop, también del equipo de los profesores Gregori y Rifé, nos ofrece los nuevos planteamientos para la descripción y catalogación del fondo musical de la catedral de Lleida. Divide este fondo en tres grupos: pergaminos, impresos y manuscritos. Subraya que gran parte del fondo de manuscritos es obra de Magí Pontí i Ferrer, nacido en Manresa en 1815 y formado en el monasterio de Montserrat; ejerció como primer organista y maestro de capilla durante 48 años en la catedral de Lleida.Ester Garcia Llop, également membre de l'équipe des professeurs Gregori et Rifé, nous offre une brève introduction historique, suivie des nouvelles méthodes d'approche appliquées à la description et au catalogage du fonds musical de la cathédrale de Lérida. Elle divise ce fonds en trois groupes : parchemins, imprimés et manuscrits. Ester Garcia Llop indique également que l'on doit la plupart du fonds de manuscrits à Magí Pontí i Ferrer. Ce dernier naquit à Manresa en 1815 et fut formé dans le monastère de Montserrat, puis remplit les fonctions de premier organiste et de maître de chapelle durant 48 ans dans la cathédrale de Lérida.After a brief historical introduction, Ester Garcia Llop, also a member of the team under Professors Gregori and Rifé, offers new thoughts on the description and compilation of the musical fund of the Cathedral of Lleida. This fund is divided into three groups: parchment, printed and manuscripts. It emphasizes that a large part of the fund of manuscripts is the work of Magí Pontí i Ferrer, born in Manresa in 1815 and educated at the monastery of Montserrat. He was the first organist and the chapel master for 48 years at the Cathedral of Lleida.Nach einer kurzen geschichtlichen Einführung beschreibt Ester Garcia Llop, ebenfalls Mitglied des Teams der Professoren Gregori und Rifé die neuen Gedanken zur Beschreibung und Katalogisierung der Musikalischen Grundlagen der Kathedrale von Lleida. Sie teilt diese Grundlagen in drei Gruppen ein: Pergamente, Drucke und Manuskripte. Sie weist vor allem auf die Tatsache hin, dass ein Grossteil Werke von Magí Pontí i Ferrer, geboren in Manresa im Jahr 1815, ausgebildet im Kloster von Montserrat, sind; er war 48 Jahre lang erster Organist und Kapellmeister der Kathedrale von Lleida
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