Dissipative Unified Dark Fluid Model

We consider a unified dissipative dark fluid model. Our fluid contains an adiabatic part plus a bulk viscous one. The adiabatic part has the ability to asymptote between two power laws and so can interpolate between the dust and dark energy equations of state at early and late times. The dissipative part is a bulk viscous part with constant viscosity coefficient. The model is analyzed using the phase space methodology which helps to understand the dynamical behavior of the model in a robust manner without reference to the system solution. The parameters of the model are constrained through its asymptotic behavior and also through many observational constraints. We solve the Hubble parameter equation using numerical methods and results are plotted against the newest set of Hubble data. The model is tested using the $Om(z)$ test which shows that this model although is a quintessence-like model, it slides through the phantom barrier. We study the model expectations for the evolution of the universe by studying the evolution of the deceleration parameter, the density of the universe, the effective equation of state parameter of the model and of its underlying dark energy package. We estimate the value of the present day viscosity coefficient of the cosmic fluid as $8 \times 10^6 Pa.s$, which agrees with the work of many authors, e.g., Velten and Schwartz [26], Wang and Meng [27], and Sasidharan and Mathew [29]. We argue that this model is able to explain the behavior of the universe evolution

A Viable Dark Fluid Model

We Consider a cosmological model based on a generalization of the equation of state proposed by Nojiri and Odintsov [46] and \v{S}tefan\v{c}i'c [47], [48]. We argue that this model works as a dark fluid model which can interpolate between dust equation of state and the dark energy equation of state. We show how the asymptotic behavior of the equation of state constrained the parameters of the model. The causality condition for the model is also studied to constrain the parameters and the fixed points are tested to determine different solution classes. Observations of Hubble diagram of SNe Ia supernovae are used to further constrain the model. We present an exact solution of the model and calculate the luminosity distance and the energy density evolution. We also calculate the deceleration parameter to test the state of the universe expansion.Comment: 16 pages and 5 figure

Reconstruction of f(R)f(R) Gravity from Cosmological Unified Dark Fluid Model

In this work, we reconstruct the cosmological unified dark fluid model proposed previously by Elkhateeb \cite{Elkhateeb:2017oqy} in the framework of $f(R)$ gravity. Utilizing the equivalence between the scalar-tensor theory and the $f(R)$ gravity theory, the scalar field for the dark fluid is obtained, whence the $f(R)$ function is extracted and its viability is discussed. The $f(R)$ functions and the scalar field potentials have then been extracted in the early and late times of asymptotically de Sitter spacetime. The ability of our function to describe early time inflation is also tested. The early time scalar field potential is used to derive the slow roll inflation parameters. Our results of the tensor-to-scalar ratio $r$ and the scalar spectral index $n_s$ are in good agreement with results from Planck-2018 TT+TE+EE+lowE data for the model parameter $m > 2$.Comment: 11 pages and 2 figure

The acoustical design of the new lecture auditorium, Faculty of Law, Ain Shams University

AbstractThis work represents the main acoustical design phases for the new lecture auditorium in the Faculty of Law, Ain Shams University, Cairo/Egypt. The work also discusses some of the architectural details that were used and have a direct effect on the acoustical environment inside the auditorium. The work compares finally among field measurements (that were recorded after the construction in the unoccupied auditorium), the values expected during the acoustic design phase (utilizing ODEON ver. 4.2, assuming the occupied case), and the optimum values for speech intelligibility indicators that were considered in this work (T20, D50, STI, LAeq, and the background noise). Field measurements that were recorded utilizing MLSSA system showed that the finishing materials used successfully fulfilled a good level of speech intelligibility in the auditorium. The estimated reverberation timeT20-EOC for the occupied room (based on the measured unoccupiedT20-M) was close to the optimum especially in mid and high frequency bands. The measured D50 (unoccupied) was found to be within its acceptable range. The measured STI value (unoccupied) was “Fair, 0.49”. The measurements of LAeq indicated the uniformity of the acoustical field in the room. The noticed problem was a relatively high background noise (NC-40) due to the utilization of natural ventilation which directly contradicts the principles of room isolation

Integrated Formation Evaluation Study in Cliff Head Field, Northern Perth Basin, Western Australia

A new technique was implemented to unlock the reservoir characterisation in complex reservoirs. Integration between the conventional density log and the NMR free fluid index has been carried out, through which a high-resolution electrofacies have been classified using a new technique, named the Equivalent Flow Zone Indicator (EFZI). Further, the permeability and water saturation were calculated through new workflows, both are EFZI dependent, with which a high-resolution parameterisation could be achieved for highly complicated reservoirs