Noether Symmetry Approach in Scalar-Torsion f(T,ϕ)f(T,\phi) Gravity

The Noether Symmetry approach is applied to study an extended teleparallel $f(T,\phi)$ gravity that contains the torsion scalar $T$ and the scalar field $\phi$ in the context of an Friedmann-Lema\^{i}tre-Robertson-Walker space-time. We investigate the Noether symmetry approach in $f(T,\phi)$ gravity formalism with the specific form of $f(T,\phi)$ and analyze how to demonstrate a nontrivial Noether vector. The Noether symmetry method is a helpful resource for generating models and finding out the exact solution of the Lagrangian. In this article, we go through how the Noether symmetry approach enables us to define the form of the function $f(T,\phi)$ and obtain exact cosmological solutions. We also find the analytical cosmological solutions to the field equations, that is consistent with the Noether symmetry. Our results demonstrate that the obtained solutions enable an accelerated expansion of the Universe. We have also obtained the present value of the Hubble parameter, deceleration parameter, and effective equation of state parameter, which is fit in the range of current cosmological observations.Comment: 12 pages, Accepted version European Physical Journal

Ab-initio study of the bandgap engineering of Al(1-x)Ga(x)N for optoelectronic applications

A theoretical study of Al(1-x)Ga(x)N, based on full-potential linearized augmented plane wave method, is used to investigate the variations in the bandgap, optical properties and non-linear behavior of the compound with the variation of Ga concentration. It is found that the bandgap decreases with the increase of Ga in Al(1-x)Ga(x)N. A maximum value of 5.5 eV is determined for the bandgap of pure AlN which reaches to minimum value of 3.0 eV when Al is completely replaced by Ga. The static index of refraction and dielectric constant decreases with the increase in bandgap of the material, assigning a high index of refraction to pure GaN when compared to pure AlN. The refractive index drops below 1 for photon energies larger than 14 eV results group velocity of the incident radiation higher than the vacuum velocity of light. This astonishing result shows that at higher energies the optical properties of the material shifts from linear to non-linear. Furthermore, frequency dependent reflectivity and absorption coefficients show that peak value of the absorption coefficient and reflectivity shifts towards lower energy in the UV spectrum with the increase in Ga concentration. This comprehensive theoretical study of the optoelectronic properties of the alloys is presented for the first time which predicts that the material can be effectively used in the optical devices working in the visible and UV spectrum.Comment: 18 pages, 7 figure

On the time dependent Schwarzschild - de Sitter spacetime

An imperfect cosmic fluid with energy flux is analyzed. Even though its energy density $\rho$ is positive, the pressure $p = -\rho$ due to the fact that the metric is asymptotically de Sitter. The kinematical quantities for a nongeodesic congruence are computed. The scalar expansion is time independent but divergent at the singularity $r = 2m$. Far from the central mass $m$ and for a cosmic time $\bar{t} << H^{-1}$, the heat flux $q$ does not depend on Newton's constant $G$.Comment: 8 pages, no figures, Sections 3 and 5 enlarged, one reference adde

Discretization-Based Feature Selection as a Bilevel Optimization Problem

Discretization-based feature selection (DBFS) approaches have shown interesting results when using several metaheuristic algorithms, such as particle swarm optimization (PSO), genetic algorithm (GA), ant colony optimization (ACO), etc. However, these methods share the same shortcoming which consists in encoding the problem solution as a sequence of cut-points. From this cut-points vector, the decision of deleting or selecting any feature is induced. Indeed, the number of generated cut-points varies from one feature to another. Thus, the higher the number of cut-points, the higher the probability of selecting the considered feature; and vice versa. This fact leads to the deletion of possibly important features having a single or a low number of cut-points, such as the infection rate, the glycemia level, and the blood pressure. In order to solve the issue of the dependency relation between the feature selection (or removal) event and the number of its generated potential cut-points, we propose to model the DBFS task as a bilevel optimization problem and then solve it using an improved version of an existing co-evolutionary algorithm, named I-CEMBA. The latter ensures the variation of the number of features during the migration process in order to deal with the multimodality aspect. The resulting algorithm, termed bilevel discretization-based feature selection (Bi-DFS), performs selection at the upper level while discretization is done at the lower level. The experimental results on several high-dimensional datasets show that Bi-DFS outperforms relevant state-of-the-art methods in terms of classification accuracy, generalization ability, and feature selection bias

Uncertainty-wise software anti-patterns detection: A possibilistic evolutionary machine learning approach

Context: Code smells (a.k.a. anti-patterns) are manifestations of poor design solutions that can deteriorate software maintainability and evolution. Research gap: Existing works did not take into account the issue of uncertain class labels, which is an important inherent characteristic of the smells detection problem. More precisely, two human experts may have different degrees of uncertainty about the smelliness of a particular software class not only for the smell detection task but also for the smell type identification one. Unluckily, existing approaches usually reject and/or ignore uncertain data that correspond to software classes (i.e. dataset instances) with uncertain labels. Throwing away and/or disregarding the uncertainty factor could considerably degrade the detection/identification process effectiveness. From a solution approach viewpoint, there is no work in the literature that proposed a method that is able to detect and/or identify code smells while preserving the uncertainty aspect. Objective: The main goal of our research work is to handle the uncertainty factor, issued from human experts, in detecting and/or identifying code smells by proposing an evolutionary approach that is able to deal with anti-patterns classification with uncertain labels. Method: We suggest Bi-ADIPOK, as an effective search-based tool that is capable to tackle the previously mentioned challenge for both detection and identification cases. The proposed method corresponds to an EA (Evolutionary Algorithm) that optimizes a set of detectors encoded as PK-NNs (Possibilistic K-nearest neighbors) based on a bi-level hierarchy, in which the upper level role consists on finding the optimal PK-NNs parameters, while the lower level one is to generate the PK-NNs. A newly fitness function has been proposed fitness function PomAURPC-OVA_dist (Possibilistic modified Area Under Recall Precision Curve One-Versus-All_distance, abbreviated PAURPC_d in this paper). Bi-ADIPOK is able to deal with label uncertainty using some concepts stemming from the Possibility Theory. Furthermore, the PomAURPC-OVA_dist is capable to process the uncertainty issue even with imbalanced data. We notice that Bi-ADIPOK is first built and then validated using a possibilistic base of smell examples that simulates and mimics the subjectivity of software engineers opinions. Results: The statistical analysis of the obtained results on a set of comparative experiments with respect to four relevant state-of-the-art methods shows the merits of our proposal. The obtained detection results demonstrate that, for the uncertain environment, the PomAURPC-OVA_dist of Bi-ADIPOK ranges between 0.902 and 0.932 and its IAC lies between 0.9108 and 0.9407, while for the certain environment, the PomAURPC-OVA_dist lies between 0.928 and 0.955 and the IAC ranges between 0.9477 and 0.9622. Similarly, the identification results, for the uncertain environment, indicate that the PomAURPC-OVA_dist of Bi-ADIPOK varies between 0.8576 and 0.9273 and its IAC is between 0.8693 and 0.9318. For the certain environment, the PomAURPC-OVA_dist lies between 0.8613 and 0.9351 and the IAC values are between 0.8672 and 0.9476. With uncertain data, Bi-ADIPOK can find 35% more code smells than the second best approach (i.e., BLOP). Furthermore, Bi-ADIPOK has succeeded to reduce the number of false alarms (i.e., misclassified smelly instances) by 12%. In addition, our proposed approach can identify 43% more smell types than BLOP and reduces the number of false alarms by 32%. The same results have been obtained for the certain environment, demonstrating Bi-ADIPOK's ability to deal with such environment

Dynamical systems analysis in f(T,ϕ)f(T,\phi) gravity

Teleparallel based cosmological models provide a description of gravity in which torsion is the mediator of gravitation. Several extensions have been made within the so-called Teleparallel equivalent of general relativity which is equivalent to general relativity at the level of the equations of motion where attempts are made to study the extensions of this form of gravity and to describe more general functions of the torsion scalar $T$. One of these extensions is $f(T,\phi)$ gravity; $T$ and $\phi$ respectively denote the torsion scalar and scalar field. In this work, the dynamical system analysis has been performed for this class of theories to obtain the cosmological behaviour of a number of models. Two models are presented here with some functional form of the torsion scalar and the critical points are obtained. For each critical point, the stability behaviour and the corresponding cosmology are shown. Through the graphical representation the equation of state parameter and the density parameters for matter-dominated, radiation-dominated and dark energy phase are also presented for both the models.Comment: 15 pages, 4 figure

Morogoro Regional and District Projections

\ud This report presents population projections for the period 2003 to 2025 for the Morogoro Region and its districts. The projections were made using a Cohort Component Method (Spectrum System), whereby three components responsible for population change, namely: mortality, fertility and migration were projected separately as well as HIV/AIDS prevalence. The projected components were then applied to 2002 midyear base population in order to come up with the desired projections from 2003 to 2025. The report gives mortality, fertility, migration and HIV/AIDS assumptions, and shows Morogoro’s demographic and socio-economic future trends. The results include estimated population by sex in single years and five-year age groups as well as some demographic indicators. Population growth for the period 2003 to 2025 shows a decrease in growth rates. The projections show that population growth rate will decrease from 2.3 percent in 2003 (with a population of 1,794,815) to 1.7 percent in 2025 (with a population of 2,818,784). Sex Ratio at birth is projected to increase from 99 male births per 100 females in 2003 to 101 male births per 100 females in 2025. Mortality estimates show that Infant Mortality Rate (IMR) is expected to decline for both sexes from 105 deaths per 1,000 live births in 2003 to 63 deaths per 1,000 live births in 2025. Under Five Mortality Rate (U5MR) for both sexes will also decline from 171 deaths per 1,000 live births in 2003 to 98 deaths per 1,000 live births in the year 2025. The mortality projected estimates further show that the life expectancy at birth for males is slightly lower compared to that of females. Life expectancy at birth for Morogoro will increase from 50 years in 2003 to 54 years in 2025 for both sexes. For male population, life expectancy at birth will increase from 50 years in year 2003 to 54 years in 2025, while for female population, the life expectancy at birth will increase from 50 years in 2003 to 55 years in 2025. On fertility, TFR will decline from 5.0 children per woman in 2003 to 3.7 children per woman in 2025.\u

Mtwara Regional and District Projections.

\ud This report presents population projections for the period 2003 to 2025 for Mtwara region and its districts. The projections were made using a Cohort Component Method (Spectrum System), whereby three components responsible for population change, namely: mortality, fertility and\ud migration were projected separately as well as HIV/AIDS prevalence. The projected components were then applied to 2002 midyear base population in order to come up with the desired projections from 2003 to 2025. The report gives mortality, fertility, migration and HIV/AIDS assumptions, and shows Mtwara’s demographic and socio-economic future trends. The results include estimated population by sex in single years and five-year age groups as well as some demographic indicators. Population growth for the period 2003 to 2025 shows an increase from 1.8 percent in 2003 (with a population of 1,145,655) to 2.0 percent in 2009 (with a population of 1,297,751) and will decrease gradually to 1.8 in 2025 (with a population of 1,724,679). Sex Ratio at birth is projected to increase from 90 male births per 100 females in 2003 to 97 male births per 100 females in 2025. Mortality estimates show that Infant Mortality Rate (IMR) is expected to decline for both sexes from 143 deaths per 1,000 live births in 2003 to 84 deaths per 1,000 live births in 2025. Under Five Mortality Rate (U5MR) for both sexes will also decline from 238 deaths per 1,000 live births in 2003 to 134 deaths per 1,000 live births in the year 2025. Life expectancy at birth for Mtwara will increase from 43 years in 2003 to 48 years in 2025 for both sexes. For male population, life expectancy at birth will increase from 43 years in year 2003 to 48 years in 2025, while for female population the life expectancy at birth will increase from 42 years in 2003 to 48 years in 2025. On fertility, TFR will decline from 4.9 children per woman in 2003 to 4.6 children per woman in 2025.\u

Nigerian scam e-mails and the charms of capital

So-called '419' or 'advance-fee' e-mail frauds have proved remarkably successful. Global losses to these scams are believed to run to billions of dollars. Although it can be assumed that the promise of personal gain which these e-mails hold out is part of what motivates victims, there is more than greed at issue here. How is it that the seemingly incredible offers given in these unsolicited messages can find an audience willing to treat them as credible? The essay offers a speculative thesis in answer to this question. Firstly, it is argued, these scams are adept at exploiting common presuppositions in British and American culture regarding Africa and the relationships that are assumed to exist between their nations and those in the global south. Secondly, part of the appeal of these e-mails lies in the fact that they appear to reveal the processes by which wealth is created and distributed in the global economy. They thus speak to their readers’ attempts to map or conceptualise the otherwise inscrutable processes of that economy. In the conclusion the essay looks at the contradictions in the official state response to this phenomena