Induced automorphisms on irreducible symplectic manifolds

We introduce the notion of induced automorphisms in order to state a criterion to determine whether a given automorphism on a manifold of K3[n]-type is, in fact, induced by an automorphism of a K3 surface, and the manifold is a moduli space of stable objects on the K3. This criterion is applied to the classification of non-symplectic prime order automorphisms on manifolds of K3[2]-type, and we prove that almost all cases are covered. Variations of this notion and the above criterion are introduced and discussed for the other known deformation types of irreducible symplectic manifolds. Furthermore, we provide a description of the picard lattice of several irreducible symplectic manifolds having a lagrangian fibration

The study of air fuel ratio for open furnace MILD combustion of biogas on bluff-body burner

Economical fuel cost is very critical in the heating industry. Lean combustion with high air fuel ratio (AFR) is normally practiced by the industry. Low air fuel ratio or rich combustion will result in unburned hydrocarbons (UHC). UHC is a waste and pollution to the environment. This paper discussed on the modelling of air fuel ratio for the moderate and intense low oxygen dilution (MILD) combustion of biogas on bluff-body burner. Biogas is a low calorific value (LCV) gas which was formulated by using 50% methane, 20% hydrogen and 30% carbon dioxide. AFR is the ratio of air and fuel injected to the combustion chamber. Nozzle outlet size for air and fuel plays important role to determine AFR. In this study, the air and fuel nozzle size ratio used is 23:1. The AFR will be evaluated based on the UHC produced by the combustion. Stoichiometric AFR occurred when zero UHC and zero excess oxygen flow through the EGR pipe. The result shows that when AFR is 4.0, zero UHC was detected in the EGR. UHC in EGR will be waste and create unwanted combustion at the wrong location

Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei: I. Comparing the Photoionization and Reverberation Techniques

The masses and emission-line region sizes of Active Galactic Nuclei (AGNs) can be measured by ``reverberation-mapping'' (measuring the lag of the emission-line luminosity after changes in the continuum). We use tis technique to calibrate similar size and mass estimates made by photoionization models of the AGN line-emitting regions. We compile a sample of 19 AGNs with reliable reverberation and spectroscopy data, twice the number available previously. The data provide strong evidence that the BLR size and the emission-line width measure directly the central mass. Two methods are used to estimate the distance of the broad emission-line region (BLR) from the ionizing source: the photoionization method (available for many AGNs but has large intrinsic uncertainties), and the reverberation method (gives very reliable distances, but available for only a few objects). The distance estimate is combined with the velocity dispersion, derived from the broad Hb line profile, to estimate the virial mass. Comparing the central masses calculated with the reverberation method to those calculated using a photoionization model, we find a highly significant, nearly linear correlation. This provides a calibration of the photoionization method on the objects with presently available reverberation data, which should enable mass estimates for all AGNs with measured Hb line width. Comparing the BLR sizes given by the two methods also enables us to estimate the ionizing EUV luminosity which is directly unobservable. We find it to be typically ten times the visible (monochromatic luminosity at 5100A). The inferred Eddington ratio of the individual objects in our sample are 0.001-0.03 (visible luminosity) and 0.01-0.3 (ionizing luminosity).Comment: 27 pages Latex, 8 figures. Accepted for publication in the Astrophysical Journa

X-ray variability and spectral scaling: a measure of BLR sizes in AGN

We apply a new method of determination of the size of the broad emission-line region (BLR) in active galactic nuclei. This method relates the radius of the broad-line region of AGN to the soft X-ray luminosity and spectral index. Comparing the BLR distances calculated from our photoionization scaling model to the BLR distances determined by reverberation mapping shows that the scaling law agrees with the $R\sim L^{1/2}$ empirical relation. We investigate a complimentary method of estimating the BLR distance - based on the Keplerian broadening of the emission lines and the central mass estimated from X-ray variability.Comment: 4 page latex file, 2 figs. Complete uuencoded compressed PS file is also available at ftp://saba.fiz.huji.ac.il/~pub/wandel/blrx_ts.uu or at http://shum.cc.huji.ac.il/~amri/papers/blrx_ts(tex,ps) to appear in Proc. of Astronomical Time Serie

Keplerian Motion of Broad-Line Region Gas as Evidence for Supermassive Black Holes in Active Galactic Nuclei

Emission-line variability data on NGC 5548 argue strongly for the existence of a mass of order 7 x 10^7 solar masses within the inner few light days of the nucleus in the Seyfert 1 galaxy NGC 5548. The time-delayed response of the emission lines to continuum variations is used to infer the size of the line-emitting region, and these determinations are combined with measurements of the Doppler widths of the variable line components to estimate a virial mass. The data for several different emission lines spanning an order of magnitude in distance from the central source show the expected V proportional to r^{-1/2} correlation and are consistent with a single value for the mass.Comment: 9 pages, 2 Figures. accepted by ApJ Letter

Supermassive Black Holes in Active Galactic Nuclei. I. The Consistency of Black Hole Masses in Quiescent and Active Galaxies

We report the first results of a program to measure accurate stellar velocity dispersions in the bulges of the host galaxies of active galactic nuclei (AGNs) for which accurate black hole (BH) masses have been determined via reverberation mapping. We find good agreement between BH masses obtained from reverberation mapping, and from the M(BH) - sigma relation as defined by quiescent galaxies, indicating a common relationship between active and quiescent black holes and their large-scale environments.Comment: Submitted to ApJ

Evidence for Supermassive Black Holes in Active Galactic Nuclei from Emission-Line Reverberation

Emission-line variability data for Seyfert 1 galaxies provide strong evidence for the existence of supermassive black holes in the nuclei of these galaxies, and that the line-emitting gas is moving in the gravitational potential of that black hole. The time-delayed response of the emission lines to continuum variations is used to infer the size of the line-emitting region, which is then combined with measurements of the Doppler widths of the variable line components to estimate a virial mass. In the case of the best-studied galaxy, NGC 5548, various emission lines spanning an order of magnitude in distance from the central source show the expected velocity proportional to inverse square root of the distance correlation between distance and line width, and are thus consistent with a single value for the mass. Two other Seyfert galaxies, NGC 7469 and 3C 390.3, show a similar relationship. We compute the ratio of luminosity to mass for these three objects and the narrow-line Seyfert 1 galaxy NGC 4051 and find that that the gravitational force on the line-emitting gas is much stronger than radiation pressure. These results strongly support the paradigm of gravitationally bound broad emission-line region clouds.Comment: 10 pages, 2 figures, Accepted for publication in Astrophysical Journal Letter

Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei; 1, Comparing the Photoionization and Reverberation Techniques

The masses and emission-line region sizes of Active Galactic Nuclei (AGNs) can be measured by ``reverberation-mapping'' (measuring the lag of the emission-line luminosity after changes in the continuum). We use tis technique to calibrate similar size and mass estimates made by photoionization models of the AGN line-emitting regions. We compile a sample of 19 AGNs with reliable reverberation and spectroscopy data, twice the number available previously. The data provide strong evidence that the BLR size and the emission-line width measure directly the central mass. Two methods are used to estimate the distance of the broad emission-line region (BLR) from the ionizing source: the photoionization method (available for many AGNs but has large intrinsic uncertainties), and the reverberation method (gives very reliable distances, but available for only a few objects). The distance estimate is combined with the velocity dispersion, derived from the broad Hb line profile, to estimate the virial mass. Comparing the central masses calculated with the reverberation method to those calculated using a photoionization model, we find a highly significant, nearly linear correlation. This provides a calibration of the photoionization method on the objects with presently available reverberation data, which should enable mass estimates for all AGNs with measured Hb line width. Comparing the BLR sizes given by the two methods also enables us to estimate the ionizing EUV luminosity which is directly unobservable. We find it to be typically ten times the visible (monochromatic luminosity at 5100A). The inferred Eddington ratio of the individual objects in our sample are 0.001-0.03 (visible luminosity) and 0.01-0.3 (ionizing luminosity)

Design and development of mild combustion burner

This paper discussed the design and development of the Moderate and Intense Low oxygen Dilution (MILD) combustion burner using Computational Fluid Dynamics (CFD) simulations. The CFD commercial package was used to simulate preliminary designs for the burner before the final design was sent to workshop for the fabrication. The burner is required to be a non-premixed and open burner. To capture and use the exhaust gas, the burner was enclosed within a large circular shaped wall with an opening at the top. An external EGR pipe was used to transport the exhaust gas which was mixed with the fresh oxidant. To control the EGR and exhaust flow, butterfly valves were installed at the top opening as a damper to close the exhaust gas flow at the certain ratio for EGR and exhaust out to atmosphere. High temperature fused silica glass windows were installed to view and capture images of the flame and analyse the flame propagation. The burner simulation shows that MILD combustion was achieved for the oxygen mole fraction between 3-13%. The final design of the burner was fabricated and ready for the experimental validation

MILD Combustion: A Technical Review Towards Open Furnace Combustion

Moderate or Intense Low oxygen Dilution (MILD) combustion is one of the best alternative new technologies for clean and efficient combustion. MILD combustion has been proven to be a promising combustion technology for industrial applications with decreased energy consumption due to the uniformity of temperature distribution, also producing low NO and CO emissions. This article provides a review and discussion of the recent research and development in MILD. Furthermore, the problems and focuses are summarized with some suggestions and therefore presented on upgrading an application of MILD in the future. Currently MILD combustion has been applied in closed furnace. For closed furnace, the preheating supply air is no longer required since the recirculation inside the enclosed furnace will self preheats the supply air and self dilutes the oxygen in the combustion chamber. The possibility of using open furnace MILD combustion was discussed and reviewed