Cosmo-dynamics and dark energy with a quadratic EoS: anisotropic models, large-scale perturbations and cosmological singularities

In general relativity, for fluids with a linear equation of state (EoS) or scalar fields, the high isotropy of the universe requires special initial conditions, and singularities are anisotropic in general. In the brane world scenario anisotropy at the singularity is suppressed by an effective quadratic equation of state. There is no reason why the effective EoS of matter should be linear at the highest energies, and a non-linear EoS may describe dark energy or unified dark matter (Paper I, astro-ph/0512224). In view of this, here we study the effects of a quadratic EoS in homogenous and inhomogeneous cosmological models in general relativity, in order to understand if in this context the quadratic EoS can isotropize the universe at early times. With respect to Paper I, here we use the simplified EoS P=alpha rho + rho^2/rho_c, which still allows for an effective cosmological constant and phantom behavior, and is general enough to analyze the dynamics at high energies. We first study anisotropic Bianchi I and V models, focusing on singularities. Using dynamical systems methods, we find the fixed points of the system and study their stability. We find that models with standard non-phantom behavior are in general asymptotic in the past to an isotropic fixed point IS, i.e. in these models even an arbitrarily large anisotropy is suppressed in the past: the singularity is matter dominated. Using covariant and gauge invariant variables, we then study linear perturbations about the homogenous and isotropic spatially flat models with a quadratic EoS. We find that, in the large scale limit, all perturbations decay asymptotically in the past, indicating that the isotropic fixed point IS is the general asymptotic past attractor for non phantom inhomogeneous models with a quadratic EoS. (Abridged)Comment: 16 pages, 6 figure

Non-reacting Flow Analysis from Combustor Inlet to Outlet using Computational Fluid Dynamics Code

This paper describes non-reacting flow analysis of a gas turbine combustion system. The method is based on the solution of Navier-Strokes equations using generalised non-orthogonal coordinate system. The turbulence effects are modelled through the renormalisation group k-E model. The method has been applied to a practical gas turbine combustor. The combustionsystem includes swirler vane passages, fuel nozzles, rotor bleed, customer bleed, air-blast atomiser, swirl cone, and all holes in primary , dilution , dome, flare, and cooling ring. Thetotal geometry has been created using the pre-processors GAMBIT and CATIA, and the meshing has been done using GAMBIT, and the analysis carried out in a FLUENT solver. The interaction between the diffuser and the combustor external flows plays a key role in controlling the pressure loss, air flow distribution around the combustor liner, durability, and stability. The aero gas turbine combustor designs are generally guided by experimental methods and past experience; however, experimental methods are inherently slow, costly, especially at hightemperature engine-operating conditions. These drawbacks and the growing need to understand the complex flow-field phenomenon involved, have led to the development of a numericalmodel for predicting flow in the gas turbine combustor. These models are used to optimise the design of the combustor and its subcomponents, and reduce cost, time, and the number ofexperiments

Pengaruh profitabilitas, struktur modal, ukuran perusahaan, likuiditas dan kebijakan dividen terhadap nilai perusahaan

The value of the company is the company's performance which can be seen from the stock price formed due to the demand and supply of the capital market which gives speculation of the public's assessment of the company's performance. This study aims to examine profitability, capital structure, firm size, liquidity and dividend policy on firm value in mining sector manufacturing companies listed on the Indonesia Stock Exchange for the 2017-2021 period.sampling technique in this study was using the purposive sampling method with the criteria for manufacturing companies in the mining sector that published complete financial reports in 2017-2021 and manufacturing companies in the mining sector that had complete data relating to the variables used in this study. The analytical analysis method used is multiple linear regression analysis. The data is processed using SPSS 26. The results of this study state that profitability has a positive effect on firm value. Capital structure has a positive effect on firm value. Firm size has a positive effect on firm value. Liquidity has a positive effect on firm value. Dividend policy has a positive effect on firm value.

Product/Service Diversification Potentials in Academic Libraries of Sri Lanka

Constant innovation of technology and changing of consumer behavior and social attitudes have made customer-needs are divers and variety seeking. In economic view, this ‘Turbulence of Environment’ has created a competition among entrepreneurs and therefore, many companies today utilize various strategic application to their businesses to win this competition. This move is also common to the Library and Information Service sector. As a result, users today have many options for information seeking other than the library and academic libraries face with budgetary restrictions from their parent organizations and declining user interest towards the conventional services they provide. Librarians are compelled to seek for survival potentials and response to issues of retaining user-interest and cost recovery avenues. Like business companies, academic libraries have to apply innovative strategies to expand the market share and one of these strategic applications is to diversify their products /services in accordance with the diversity of user needs. The purpose of this paper is to examine how far the academic librarians in Sri Lanka have understood the potential of product/service diversification in their libraries and discuss of the potential framework that helps them apply the diversification strategies in academic library sector. A questionnaire based survey was administered with 51 academic librarians in Sri Lanka in order to check the already available services, possible services and impossible services against a list of services determined by literature review and professional experience of the author. The check list included three categories of services: directly related library services, indirectly related library services and unrelated services. Commonly expected services from any academic library were considered as directly related services while indirectly related services were the services which are not compulsory, but can be provided by the library. Unrelated services were the non-information services that can be provided as additional services by the library for cost recovery of profit earning purposes. Results indicated that as an average directly related services of the library were available (68%) or possible to provide (22%) by 90% libraries. Indirectly related services were available in 41% libraries and were possible by 29 % libraries while 30% libraries are not able implement them. Unrelated services were available in 13% libraries and 18% of librarians perceived them as possible in libraries. However in average 69% of librarians perceived this as impossible in their libraries. Interpretation of the study reveals that academic librarians are mostly strict to the directly related library services and have quite concern about indirectly related services. Although there are many avenues to diversify their directly or indirectly related service to serve the diversity of needs of users, only a few librarians have concentrated on diversification strategy. Unrelated services which have cost recovery potentials were very poorly implemented. Capability issues such as capital restrictions, technological barriers, lack of interest and support from higher authorities, lack of entrepreneurial view among librarians and reluctance to take risk in unrelated services were seen as issues to implement service diversification strategies. It is recommended to train librarians on areas of entrepreneurship, creative thinking and leveraging of resource capabilities. Keywords: Academic libraries, Product/Service Diversification, Diversification potentials, Strategic Application, Information Marketin