On Nonlocal Modified Gravity and its Cosmological Solutions

During hundred years of General Relativity (GR), many significant gravitational phenomena have been predicted and discovered. General Relativity is still the best theory of gravity. Nevertheless, some (quantum) theoretical and (astrophysical and cosmological) phenomenological difficulties of modern gravity have been motivation to search more general theory of gravity than GR. As a result, many modifications of GR have been considered. One of promising recent investigations is Nonlocal Modified Gravity. In this article we present a brief review of some nonlocal gravity models with their cosmological solutions, in which nonlocality is expressed by an analytic function of the d'Alembert-Beltrami operator $\Box$. Some new results are also presented.Comment: 16 page

Energy conservation and harvesting in wireless sensor networks

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Nonlocal de Sitter gravity and its exact cosmological solutions

This paper is devoted to a simple nonlocal de Sitter gravity model and its exact vacuum cosmological solutions. In the Einstein-Hilbert action with $\Lambda$ term, we introduce nonlocality by the following way: $R - 2 \Lambda = \sqrt{R-2\Lambda}\ \sqrt{R-2\Lambda} \to \sqrt{R-2\Lambda}\ F(\Box)\ \sqrt{R-2\Lambda} ,$where${F} (\Box) = 1 + \sum_{n= 1}^{+\infty} \big( f_n \Box^n + f_{-n} \Box^{-n} \big) $is an analytic function of the d'Alembert-Beltrami operator$\Box$and its inverse$\Box^{-1}$. By this way,$R$and$\Lambda$enter with the same form into nonlocal version as they are in the local one, and nonlocal operator$F(\Box)$is dimensionless. The corresponding equations of motion for gravitational field$g_{\mu\nu}$are presented. The first step in finding some exact cosmological solutions is solving the equation$\Box \sqrt{R-2\Lambda} = q \sqrt{R-2\Lambda} , $where$ q =\zeta \Lambda \quad (\zeta \in \mathbb{R})$is an eigenvalue and$\sqrt{R-2\Lambda}$is an eigenfunction of the operator$\Box .$ We presented and discussed several exact cosmological solutions for homogeneous and isotropic universe. One of these solutions mimics effects that are usually assigned to dark matter and dark energy. Some other solutions are examples of the nonsingular bounce ones in flat, closed and open universe. There are also singular and cyclic solutions. All these cosmological solutions are a result of nonlocality and do not exist in the local de Sitter case.Comment: 27 pages, 5 figures. Comments welcom

ENTREPRENEURSHIP IN THE PUBLIC UTILITY COMPANY “CITY MARKETS”

The aim of this paper is to highlight the important aspects that determine entrepreneurship and its importance to the economic development, it is their effects on the development of City Markets Co. This study was conducted using various methods such as analytical methods, interview and direct observation. In addition, hypothetical-deductive method, statistical methods and descriptive methods were also used. Data were obtained from different sources - the internal and electronic documentation of Public Utility Company (PUC) - City Markets, professional literature and the internet. The Public Utility Company City - Markets follows the rhythm of technological development intensively and adapts to the changing needs of consumers. These changes were primarily influenced by the appearance of supermarkets and megamarkets, the expansion of cashless payment system, credit cards and sprecific changes in habits, desires and tastes of customers. The Law on Communal Activities will open the possibility for cooperation with the private sector and various subcontractors, which will greatly contribute to the development strategy for the future development of market activity

INFLUENCE OF CLIMATIC CONDITIONS ON YIELD AND PROFITABILITY OF QUINCE BRANDY PRODUCTION

The aim of this study was to show how climatic conditions could affect the yield and profitability of quince brandy production. The study was conducted using various methods such as content analysis, analytical methods, interview and direct observation. In addition, hypothetical-deductive method, statistical methods and descriptive methods were also used. Data were obtained from different sources i.e. the internal documentation of agricultural holding where the quince, as a raw material for production of brandy was produced, the internal documentation of distillery, as well as professional literature and the internet. The analysis was done for the period 2013 - 2016. The study showed that climatic conditions can affect the yield and profitability of quince brandy production, and the production of quince brandy in analyzed years was profitable

Stark Widths of Na IV Spectral Lines

Sodium is a very important element for the research and analysis of astrophysical, laboratory, and technological plasmas, but neither theoretical nor experimental data on Stark broadening of Na IV spectral lines are present in the literature. Using the modified semiempirical method of Dimitrijević and Konjević, here Stark widths have been calculated for nine Na IV transitions. Na IV belongs to the oxygen isoelectronic sequence, and we have calculated Stark widths belonging to singlets, triplets, and quintuplets, as well as with different parent terms. This is used to discuss similarities within one transition array with different multiplicities and parent terms. Additionally, calculated widths will be implemented in the STARK-B database (http://stark-b.obspm.fr) which is also a part of the Virtual Atomic and Molecular Data Center (VAMDC—http://www.vamdc.org/

Energetski bilans proizvodnje rasada paradajza i krastavca u zaštićenom prostoru

Greenhouse production is most energy consuming branch in agriculture and in same time with lowest energy efficiency. Concerning the fact that energy input in greenhouse production has a highest share in product market price, more detailed energy analysis must be taken. In this paper energy analysis of tomato and cucumber seedlings production is given. Tomato and cucumber seedling were produced in double plastic covered tunnel. Energy consumption and energy productivity per seedling were calculated.Proizvodnja povrća u zaštićenom prostoru predstavlja granu poljoprivrede sa najvećom potrošnjom energije i niskom energetskom efikasnošću. Utrošena energija u proizvodnji povrća čini najveći deo u strukturi cene koštanja gotovog proizvoda. Otuda i potreba da se detaljnije ispitaju svi energetski inputi, kako bi se povećala energetska efikasnost proizvodnje i samim tim smanjila cena gotovog proizvoda. U ovom radu su definisani energetski inputi (direktni i indirektni) u proizvodnji rasada paradajza i krastavca i prikazana je potrošnja energije za datu biljnu proizvodnju