Surface Structure in an Accretion Disk Annulus with Comparable Radiation and Gas Pressure

We have employed a 3-d energy-conserving radiation MHD code to simulate the vertical structure and thermodynamics of a shearing box whose parameters were chosen so that the radiation and gas pressures would be comparable. The upper layers of this disk segment are magnetically-dominated, creating conditions appropriate for both photon bubble and Parker instabilities. We find little evidence for photon bubbles, even though the simulation has enough spatial resolution to see them and their predicted growth rates are high. On the other hand, there is strong evidence for Parker instabilities, and they appear to dominate the evolution of the magnetically supported surface layers. The disk photosphere is complex, with large density inhomogeneities at both the scattering and effective (thermalization) photospheres of the evolving horizontally-averaged structure. Both the dominant magnetic support and the inhomogeneities are likely to have strong effects on the spectrum and polarization of thermal photons emerging from the disk atmosphere. The inhomogeneities are also large enough to affect models of reflection spectra from the atmospheres of accretion disks.Comment: ApJ, in pres

Analysis of Public Transport System, Hatay Example: Detection of Existing System

Today, with the development of our cities, the population density has increased and therefore many problems have arisen due to the increase of the traffic density in the city and the existing transportation systems which were previously not planned with erroneous technical infrastructure have become unable to answer. Measurements of the decision variables related to the routes, vehicles and passengers are made in order to determine the existing public transport system. These decision variables include the number of vehicles leaving service during the day, the passenger carrying capacity of the vehicles, the starting and ending times of the laps, the length of the public transport line, the number of laps made during the day, the number of passengers per vehicle, and the total number of passengers. By using these variables, the structure of the existing public transportation system is determined. Increasing the quality of public transport services in metropolitan cities and raising the quality of users in more economical conditions is only possible by incorporating business activities into an institutional structure, integrating public transportation enterprises into one and planning and managing them in a unified way. Our aim in this study is to evaluate the existing route structures, vehicle types and travel analyzes in the public transportation system in Hatay Province and evaluate the positive and negative points in the developing urban structure and to transform them into an effective and sustainable structure

Local Dynamical Instabilities in Magnetized, Radiation Pressure Supported Accretion Disks

We present a general linear dispersion relation which describes the coupled behavior of magnetorotational, photon bubble, and convective instabilities in weakly magnetized, differentially rotating accretion disks. We presume the accretion disks to be geometrically thin and supported vertically by radiation pressure. We fully incorporate the effects of a nonzero radiative diffusion length on the linear modes. In an equilibrium with purely vertical magnetic field, the vertical magnetorotational modes are completely unaffected by compressibility, stratification, and radiative diffusion. However, in the presence of azimuthal fields, which are expected in differentially rotating flows, the growth rate of all magnetorotational modes can be reduced substantially below the orbital frequency. This occurs if diffusion destroys radiation sound waves on the length scale of the instability, and the magnetic energy density of the azimuthal component exceeds the non-radiative thermal energy density. While sluggish in this case, the magnetorotational instability still persists and will still tap the free energy of the differential rotation. Photon bubble instabilities are generically present in radiation pressure dominated flows where diffusion is present. We show that their growth rates are limited to a maximum value which is reached at short wavelengths where the modes may be viewed as unstable slow magnetosonic waves. We also find that vertical radiation pressure destabilizes upward propagating fast waves, and that Alfv\'en waves can be unstable. These instabilities typically have smaller growth rates than the photon bubble/slow modes. We discuss how all these modes behave in various regimes of interest, and speculate how they may affect the dynamics of real accretion disk flows.Comment: 30 pages, 5 figures, Submitted to the Astrophysical Journa

Non-LTE Models and Theoretical Spectra of Accretion Disks in Active Galactic Nuclei. III. Integrated Spectra for Hydrogen-Helium Disks

We have constructed a grid of non-LTE disk models for a wide range of black hole mass and mass accretion rate, for several values of viscosity parameter alpha, and for two extreme values of the black hole spin: the maximum-rotation Kerr black hole, and the Schwarzschild (non-rotating) black hole. Our procedure calculates self-consistently the vertical structure of all disk annuli together with the radiation field, without any approximations imposed on the optical thickness of the disk, and without any ad hoc approximations to the behavior of the radiation intensity. The total spectrum of a disk is computed by summing the spectra of the individual annuli, taking into account the general relativistic transfer function. The grid covers nine values of the black hole mass between M = 1/8 and 32 billion solar masses with a two-fold increase of mass for each subsequent value; and eleven values of the mass accretion rate, each a power of 2 times 1 solar mass/year. The highest value of the accretion rate corresponds to 0.3 Eddington. We show the vertical structure of individual annuli within the set of accretion disk models, along with their local emergent flux, and discuss the internal physical self-consistency of the models. We then present the full disk-integrated spectra, and discuss a number of observationally interesting properties of the models, such as optical/ultraviolet colors, the behavior of the hydrogen Lyman limit region, polarization, and number of ionizing photons. Our calculations are far from definitive in terms of the input physics, but generally we find that our models exhibit rather red optical/UV colors. Flux discontinuities in the region of the hydrogen Lyman limit are only present in cool, low luminosity models, while hotter models exhibit blueshifted changes in spectral slope.Comment: 20 pages, 31 figures, ApJ in press, spectral models are available for downloading at http://www.physics.ucsb.edu/~blaes/habk

Effect of Tire Lug Height, Forward Speed and Cast Iron Ballast on Tractor Performance

The study was conducted at El Rahad Agricultural Scheme (Block 8( Sudan, during the period Feb.-May 1996 where the soil is a heavy cracking clay. The objective of the study was to improve the performance of the tractor when worn tires were used. The performance of the tractor, wheel slippage, fuel consumption and field capacity of the tractor were measured. Three levels of tire lug height were used, namely, 35 mm (new tire), 20 mm (medium worm tire) and zero mm (fully worn tire). Four levels of cast iron ballast were used, namely, zero, 63, 126 and 252 kg were distributed between rear tires. Moreover, three levels of tractor forward speed (5.6, 6.9 and 10.6 km/hr) were employed. The results indicated that there was a significant improvement in tractor performance when using worn tires through the use of cast iron ballast on the rear wheels. It was found that tires with zero mm lug height and 252 kg cast iron ballast decreased tractor wheel slippage and fuel consumption by34% and 18%, respectively, and increased tractor field capacity by 16.2 % Moreover, when tires with 20 mm lug height and 252 kg cast iron ballast were used, the slippage and fuel consumption were decreased by 41.7 % and 18.2%, respectively, and tractor field capacity was increased by 14.5%. The tractor with tires lug height of 35 mm and 252 kg cast iron ballast, decreased slippage and fuel consumption by 22% and 11.5%, respectively, and increased tractor field capacity by 13.5%

The UV Continuum of Quasars: Models and SDSS Spectral Slopes

We measure long (2200-4000 ang) and short (1450-2200 ang) wavelength spectral slopes \alpha (F_\nu proportional to \nu^\alpha) for quasar spectra from the Sloan Digital Sky Survey. The long and short wavelength slopes are computed from 3646 and 2706 quasars with redshifts in the z=0.76-1.26 and z=1.67-2.07 ranges, respectively. We calculate mean slopes after binning the data by monochromatic luminosity at 2200 ang and virial mass estimates based on measurements of the MgII line width and 3000 ang continuum luminosity. We find little evidence for mass dependent variations in the mean slopes, but a significant luminosity dependent trend in the near UV spectral slopes is observed with larger (bluer) slopes at higher luminosities. The far UV slopes show no clear variation with luminosity and are generally lower (redder) than the near UV slopes at comparable luminosities, suggesting a slightly concave quasar continuum shape. We compare these results with Monte Carlo distributions of slopes computed from models of thin accretion disks, accounting for uncertainties in the mass estimates. The model slopes produce mass dependent trends which are larger than observed, though this conclusion is sensitive to the assumed uncertainties in the mass estimates. The model slopes are also generally bluer than observed, and we argue that reddening by dust intrinsic to the source or host galaxy may account for much of the discrepancy.Comment: To be published in ApJ, 18 pages, 10 figure

Design and Development of a Photovoltaic Water Pumping

The theory of design and analysis of experiments has been primarily developed by statisticians engaged mostly in agricultural research. The theory has now found applications in other fields of research, because it is based on general principles concerning the statistical behavior of observations which arise either freely in nature or in artificial laboratory conditions (Badrldin and Kshirsagar,1990). Incomplete block designs were developed to suit experiments where the number of experimental units per block is less than the number of treatments. The concept of incomplete block designs augmented by a control was first introduced by Das (1954). He considered  the case where (q ³ 1) new treatments are introduced into the design and all included in each block. He concluded that  q should be chosen as low as possible to keep the block size to a reasonable level. Pearce (1960) considered the case where a Balanced Incomplete Block (B. I. B.) design is supplemented by a control, where the test treatments are replicated r times except the control which is  replicated r0 times, while all pairs of treatments occurs l times in blocks, the supplemented treatment occurs l0 times with any other treatment(Ture,1982). Pesek (1974) considered the case of a B. I. B. design having an extra control in each block. He utilized Rao’s general formulas to obtain the variances of the elementary treatment contrast between any pair of test treatment and any treatment and the control. He also obtained the efficiency factor of this design and showed that this design is more efficient than a B. I. B. design for comparing treatments with a control, but is less efficient for pair wise comparisons between the test treatments. Many times, for important new drugs and for serious diseases, investigations are carried out simultaneously at various locations under different climatic conditions, for a series of treatments. In such cases, the result of all such investigations need to be combined to produce an overall estimate of the effect of treatment contrast to the control. In this study the case where a control is added to each block in a B. I. B. design is considered. The variances of the elementary treatment contrast between any pair of test treatments and any treatment and the control were obtained. The general theory of inter & intra -block estimates of treatment effect when a B. I. B. design is augmented by a control was investigated, the general theory of a balanced incomplete block design is given where a control is added to each block. The estimation of weight for combining inter and intra-block estimates is also dealt with, and the weight for combining inter-block estimates of treatment contrast was also considered. The object of this study is to get a minimum variance of the treatment contrast between the inter and intra block estimates when a control treatment is added to each block in B. I. B. design