Line and Continuum Variability in Active Galaxies

We compared optical spectroscopic and photometric data for 18 AGN galaxies over 2 to 3 epochs, with time intervals of typically 5 to 10 years. We used the Multi-Object Double Spectrograph (MODS) at the Large Binocular Telescope (LBT) and compared the spectra to data taken from the SDSS database and the literature. We find variations in the forbidden oxygen lines as well as in the hydrogen recombination lines of these sources. For 4 of the sources we find that, within the calibration uncertainties, the variations in continuum and line spectra of the sources are very small. We argue that it is mainly the difference in black hole mass between the samples that is responsible for the different degree of continuum variability. In addition we find that for an otherwise constant accretion rate the total line variability (dominated by the narrow line contributions) reverberates the continuum variability with a dependency $\Delta L_{line} \propto (\Delta L_{cont.})^{\frac{3}{2}}$. Since this dependency is prominently expressed in the narrow line emission it implies that the luminosity dominating part of the narrow line region must be very compact with a size of the order of at least 10 light years. A comparison to literature data shows that these findings describe the variability characteristics of a total of 61 broad and narrow line sources.Comment: 30 pages including the appendix, 18 figures including the appendix. Accepted 2015 September 3. Received 2015 August 24; in original form 2015 July 3 in Monthly Notices of the Royal Astronomical Societ

THE CHALLENGES OF SUSTAINABLE HISTORICAL CENTERS: THE CASE OF ROSETTE, EGYPT

Historical centers of many Egyptian cities managed to survive as living cities in spite of physical decline and economic depression. Their fabric carries out the spiritual and cultural messages that communicate with their present citizens. The heritage of these historic city centers are not only Material character, but much more. Generally, the conservation of historic centers is fundamentally different from conservation of single monument. While a single monument can be kept on a chosen state of evolution, the historic centers cannot be preserved in particular state \u201cwith exception of the small areas conserved for tourist purposes\u201d. The historic centers, as living cities must meet the varying needs of citizens with sustainable transformations. The challenge is not how to preserve, but how to create dynamic living spaces and places that produce rich in cultural traditions that lead organically from the past to the future. The research will study and analyze the historical center of \u201cRosetta\u201d, which is one of the intermediate cities in northern Egypt that has a particular architectural heritage and many urban problems. The city of Rosetta (Rashid in Arabic) is located on the west bank of the Rosetta branch of the Nile, approximately 65km east of Alexandria on the Mediterranean coast. Today it is best known for the Rosetta stone, which was discovered in the Qayitbay castle in 1799. The city history passed over many periods of increase and decrease in its importance due to economical and political reasons. Its architectural heritage reveals the influence of various ages, but the most unique are merchant houses and mosques from the ottoman period. The city also has a particular suburban landscape of agricultural land and palm groves that are of great importance. Although Rosetta is no longer a leading commercial center, its citizens are employed in various typical activities, which are mainly agriculture, stocking and processing rice from the Delta, fishing and building ships and yachts. The main problem that faces the historic buildings of Rosetta is moisture from the soil, caused by an excess of underground salt water. The historic merchant houses have been the subject of many restoration projects over the past 20 years, but many of them have regularly been re-damaged by water and humidity and are currently under re-restoration. Unfortunately, some have even collapsed or were demolished. However, there are a number of activities that may take place in the historic buildings no longer used, maintaining the characteristics, such as crafts centers, libraries and cultural places that serve the local communities. Rosetta's historic center future must include renovation and modernization of basic infrastructure and development of traditional production sectors, based on the exploitation of this natural and cultural heritage to promote tourism locally and internationally. Physical restoration of the buildings is not enough to keep the historic center of the city alive, but a project for rehabilitation based on sustainability should be initiated. Not only to preserve and restore the outer shell, but inside the shell should insert some activities, social and economic dynamics that can make best use of resources and potential. The revitalization of Rosetta provides a mix of cultural, social, economic, technical and institutional that needs coordinated investments by the government. Must involve residents, landowners and all those have interest to ensure the careful maintenance and replacement of the elements of the built environment. This does not only depend on the availability of funding but also the specific technical and social skills that make up the traditional know-how. Unfortunately, many historical cities, especially the intermediate cities in Egypt suffer from lack of funds and local expertise. But the main problem is the lack of cooperation between the authorities who make the decisions

Grid impedance estimation for islanding detection and adaptive control of converters

The grid impedance is time varying due to the changing structure of the power system configuration and it can have a considerable influence on the control and stability of grid connected converters. This paper presents an online grid impedance estimation method using the output switching current ripple of a SVPWM based grid connected converter. The proposed impedance estimation method is derived from the discretised system model using two consecutive samples within the switching period. The estimated impedance is used for islanding detection and online current controller parameter adaptation. Theoretical analysis and MATLAB simulation results are presented to verify the proposed method. The effectiveness of the grid impedance estimator is validated using experimental results

Grid impedance estimation for islanding detection and adaptive control of converters

The grid impedance is time varying due to the changing structure of the power system configuration and it can have a considerable influence on the control and stability of grid connected converters. This paper presents an online grid impedance estimation method using the output switching current ripple of a SVPWM based grid connected converter. The proposed impedance estimation method is derived from the discretised system model using two consecutive samples within the switching period. The estimated impedance is used for islanding detection and online current controller parameter adaptation. Theoretical analysis and MATLAB simulation results are presented to verify the proposed method. The effectiveness of the grid impedance estimator is validated using experimental results

Hybrid active damping of LCL-filtered grid connected converter

A method for hybrid active damping in power converters connected to a weak grid using an LCL filter is proposed. It uses feedback of the grid current and capacitor voltage and is derived as an equivalent to the capacitor current feedback active damping method. A co-design procedure for the grid current controller with the proposed hybrid active damping method is presented. The robustness, system bandwidth and harmonic rejection are studied. The proposed method is applied to a single grid connected converter with variable grid inductance to investigate its ability to damp different system resonance frequencies and its effectiveness is verified via frequency domain analysis and time domain simulation

Analysis of ischaemic crisis using the informational causal entropy-complexity plane

In the present work, an ischaemic process, mainly focused on the reperfusion stage, is studied using the informational causal entropy-complexity plane. Ischaemic wall behavior under this condition was analyzed through wall thickness and ventricular pressure variations, acquired during an obstructive flow maneuver performed on left coronary arteries of surgically instrumented animals. Basically, the induction of ischaemia depends on the temporary occlusion of left circumflex coronary artery (which supplies blood to the posterior left ventricular wall) that lasts for a few seconds. Normal perfusion of the wall was then reestablished while the anterior ventricular wall remained adequately perfused during the entire maneuver. The obtained results showed that system dynamics could be effectively described by entropy-complexity loops, in both abnormally and well perfused walls. These results could contribute to making an objective indicator of the recovery heart tissues after an ischaemic process, in a way to quantify the restoration of myocardial behavior after the supply of oxygen to the ventricular wall was suppressed for a brief period.Fil: Legnani, Walter. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Universidad Nacional de Lanús; ArgentinaFil: Traversaro Varela, Francisco. Instituto Tecnológico de Buenos Aires; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Redelico, Francisco Oscar. Hospital Italiano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Quilmes; ArgentinaFil: Cymberknop, Leandro Javier. Instituto Tecnologico de Buenos Aires. Departamento de Bioingenieria; Argentina. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; ArgentinaFil: Armentano, Ricardo Luis. Universidad Tecnológica Nacional. Facultad Regional Buenos Aires; Argentina. Instituto Tecnologico de Buenos Aires. Departamento de Bioingenieria; ArgentinaFil: Rosso, Osvaldo Aníbal. Universidad de los Andes; Chile. Universidade Federal de Alagoas; Brasil. Hospital Italiano; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin