Charging effect on traversable wormholes in f(R) = R + αRm + βR−n gravity

In this paper, traversable wormholes have been studied in [Formula: see text] gravity, where [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] are constant. A simplest form of shape function and a logarithmic form of redshift function is considered to construct wormhole solutions. The range of parameters providing the wormhole solutions free from the matter violating the energy conditions is explored. Further, the effect of charge is analyzed on wormhole solutions.

A Piecewise-Defined Function for Modelling Traffic Noise on Urban Roads

In this paper, a piecewise-defined function is proposed to estimate traffic noise in urban areas. The proposed approach allows the use of the model even in the case of very low or zero flows for which the classical logarithmic form is not suitable. A model based on the proposed approach is calibrated for a real case and compared with the results obtained with a model based only on the logarithmic form. The results obtained show how the proposed piecewise-defined function, linear for low traffic flows and logarithmic for medium-high volumes, is able to better represent real noise pollution levels in all conditions. The proposed approach is particularly useful when comparing two plan scenarios from the point of view of noise effects.

Conservation laws and Darboux transformations for a 3-coupled integrable lattice equations

In this paper, we firstly establish infinitely many conservation laws of the 3-coupled integrable lattice equations by using the Riccati method. Comparing with the results obtained by Sahadevan and Balakrishnan, we not only get infinite conserved densities of the polynomial form, but also some conserved densities of logarithmic form. Secondly, Darboux transformation for the system is derived with the help of the Lax pair and gauge transformation. Finally, we obtain the exact solutions of the system with the obtained Darboux transformation, and present the soliton solutions and their figures with properly parameters.

An Assessment of Stumpage Price and the Price Index of Chinese Fir Timber Forests in Southern China Using a Hedonic Price Model

Research Highlights: Stumpage price is the most important factor affecting the value of forests. Therefore, an understanding of the factors affecting stumpage prices and trends is critical for effective forest management. Background and Objectives: Chinese fir is the most important fast-growing timber species in China, it is also the tree species with the largest trading volume in the stumpage markets of Southern China. The aim of this study was to analyze the determinants and trends of stumpage prices for Chinese fir timber forests. Materials and Methods: Data on 928 sales of Chinese fir timber forests transacted between 2007 and 2016 were gathered from the stumpage markets in Southern China. We analyzed the relationship between stumpage prices and sales characteristics using the hedonic price method (HPM) and measured the stumpage price index with a dummy time hedonic index. Results: (1) The double logarithmic form of the HPM yielded a more accurate estimate than the semi logarithmic form. The R2ad values in the nine annual prediction models were all above 80%. Stock volume made the greatest contribution to stumpage price, followed by stand age. Stand area had no significant impact on the stumpage price. (2) Stumpage prices of Chinese fir timber forests fluctuated greatly, especially in 2010 and 2015 when the sequential price indexes were 180.01% and 74.95%, respectively. Taking 2007 as the baseline, we calculated the base price index in 2016 to be 197%, with an average annual growth rate of 7.82%. (3) The stumpage market was associated with a higher degree of risk than the timber market. Conclusions: Our findings provide valuable inputs that can guide and facilitate the Chinese government’s efforts to optimize resource allocation and standardize the stumpage market.

Log-anharmonic oscillator and its large-N solution

Anharmonic oscillator is considered using an unusual, logarithmic form of the anharmonicity. The model is shown connected with the more conventional power-law anharmonicity [Formula: see text] in the limit [Formula: see text]. An efficient and user-friendly method of the solution of the model is found in the large-N expansion technique.

Cosmological evolution of non-interacting and interacting holographic dark energy model in Brans–Dicke theory

The purpose of this paper is to study the dynamics of non-interacting and interacting holographic dark energy (HDE) models in the framework of Brans–Dicke (BD) cosmology. As system’s infrared cutoff, we consider the future event horizon. The scalar function of BD theory is assumed to be a logarithmic form of scale factor, which is claimed to avoid a constant result for deceleration parameter. We investigate the cosmological implications of this model in detail. We obtain the time-dependent equation of state parameter and deceleration parameter which describe the phase transition of the Universe. We observe that the model explains the early time inflation and late time acceleration including matter-dominated phase. It is also observed that the equation of state parameter may cross phantom divide line in late time evolution. The cosmic coincidence problem is also discussed for both the models. We observe that this logarithmic form of Brans–Dicke scalar field is more appropriate to achieve a less acute coincidence problem in non-interacting model whereas a soft coincidence can be achieved if coupling parameter in interacting model has small value.

PERBANDINGAN DAN KARAKTERISTIK BEBERAPATES KONVERGENSI PADA DERET TAK HINGGA

The infinite series is an infinite sum of elements of a sequence of real numbers. A main thing related to the infinite series is to determine its convergence (convergent or divergent). Purpose this research were to analyze and determine a comparison and characteristics of each convergence test, such as: D'Alembert test, Raabe test, Gauss's test, Cauchy's Root Test, and Logarithm Test. A method used descriptive method by analyzing theories relevant to the problems discussed and based on literature study.The results showed that each convergence test had characteristics for its convergence test. The D'Alembert Ratio test is easier to use in a series that contains the formn! ,rn, and nn. Raabe test used if the ratio test obtained value limit comparison is, so the test does not give conclusion. Whereas logarithmic test is used in the infinite series that contains the logarithmic form. The Cauchy n-th root test, can be used to determine the absolute series convergence of the nth power