Open Access Original Research Article

Olivier Denis

From the perspective of quantum gravity research, since the archetypal quantum gravitational object, the black hole, was accidentally found function as a thermodynamic system, it is certainly natural to suggest that the secret of quantum gravity may lie in thermodynamic analysis. Until now, it was not possible to express the gravitational fine-grained entropy of a black hole using the rules of gravity. However, the black holes entropic information formula fills this gap by allowing a semi-classical gravitational approach to express the gravitational fine-grained entropy of black hole. The black holes entropic information formula calculates the entropy of Hawking radiation as the entangled information of the initial considered black hole, this down to the quantum level of the system, the degrees of freedom describing the black hole, and this independently of the Bekenstein-Hawking entropy area law, providing a sufficient microscopic description of how this entropy arises, showing that the process of black holes evaporation is consistent with the unitarity principle. Also, this approach avoids ultraviolet divergences. These perspectives must be understood like the fine-grained entropy formulas discovered by Ryu and Takayanagi. In fact, the black hole entropy turns out to be a special case of the Ryu-Takayanagi conjecture. The Ryu-Takayanagi formula being a general formula for the fine-grained entropy of gravity-coupled quantum systems. That put the accent on the emergence quantum gravity process through the fundamentality of the entangled quantum information.

Open Access Original Research Article

Yendouban Kolani, Komlan Déla Donald Aoukou, Kokou N’wuitcha, Magolmèèna Banna

The study of geothermal systems requires a good knowledge of heat transfers in the depth of the soil. The aim of this work is to study the distribution of temperature in the ground under the climatic conditions of Togo. The analytical and numerical solutions of unidirectional heat transfer equation assuming the soil as a semi-infinite medium are found. The analytical solution is validated by comparing the results of the present work to those found in literature. A good qualitative agreement between these results was noted. The results show that the attenuation depth decreases when the attenuation accuracy of the thermal wave increases. The analysis of the effect of moisture content indicates that the increasing in soil conductivity with moisture result in the decreasing of the attenuation depth. Soil temperature increases when increasing soil thermal diffusivity. It is found also that, soil temperatures decrease with depth and stabilize around an average value of 30°C for depths greater than about 5.8 m for all type of soil studied in the month of March which is the hottest month of the year in Togo. A gradual decrease in temperature can be seen from March to August (hot period) followed by stabilization at around 28°C with a depth of 5.8 m. The phenomenon is reversed for the months of September to February (cold period). The soil warms up slowly during the day and cools down slowly at night because of the thermal inertia of the soil. A decrease in amplitude of the thermal wave near ground surface, is observed when the Leaf Area Index (LAI) increases. However, ils influence on the stabilization depth is not very significant. Stabilization of soil temperatures in March month is observed at a depth of about 40 cm for all LAI with a value of 37°C.

Open Access Original Research Article

A. B. Suleiman, Abubakar Maigari, A. S. Gidado, Chifu E. Ndikilar

Poly(3-hexylthiophene-2,5-diyl) (P3HT) and its derivatives are polymer based materials with π conjugation framework. P3HT is useful photoelectric material and can be used in organic semiconductor devices such as PLED, OLED, Nonlinear optical devices and solar cells. In this work, a theoretical study of P3HT in the gas phase and in some solvents (methanol, thiophene, chloroform, toluene, and acetone**)** were investigated and reported based on Density Functional Theory (DFT) as implemented in Gaussian 09 package using B3LYP/6-31++G (d, p) basis set. Structural properties such as bond lengths and bond angles as well as the HUMO, LUMO, energy gap, global chemical index, thermodynamic properties, NLO and DOS of the P3HT molecule in order to determine the reactivity and stability of the molecule were obtained. The results obtained showed that the solvents have effects on the structural, electronic and non-linear-optical properties of the molecule. The optimized bond length revealed that the molecule has a stronger bond in methanol with smallest bond length of about 1.0840Å (C_{28}-H_{35}) than in gas phase and the rest of the solvents. It was observed that the molecule is more stable in methanol with HOMO-LUMO energy gap and chemical hardness of 3.8338eV and 1.9169eV respectively. This indicates that the energy gap and chemical hardness of P3HT molecule increase with the increase in polarity and dielectric constants of the solvents. The energy gap obtained is compared with the one in literature \((3.10 \mathrm{eV})\). This indicates that the reported energy-gap leads by about \(0.7 \mathrm{eV}\). The calculations of thermodynamic properties indicate that P3HT molecule has the highest value of specific heat capacity \((\mathrm{CV})\), that is \(152.307 \mathrm{Cv}(\mathrm{Kcal} / \mathrm{Mol})\) in methanol, toluene has the highest value of entropy as \(266.960\) (Kcal/Mol), and thiophene has the highest value of zero-point vibrational energy (ZPVE) as \(455.37486 \mathrm{Kcal} / \mathrm{Mol}\). The NLO properties show that methanol has the highest value of total dipole moment ( \(\mu_{\text {tat }}\) ) as \(1.01764\) a u while acetone has the highest value of first order hyperpolarizability ( ( tot) as \(4.4447 \times 10^{-30}\) esu than the rest of the solvents. The values obtained for the first order hyperpolarizability for P3HT in acetone is about 12 times than that of the urea molecule, \(\left(0.3728 \times 10^{-30} \mathrm{esu}\right)\) which is commonly used for the comparison of NLO properties The results of the \(I R\) spectra show that the studied molecule was stable in both the gas phase and in solvents since no imaginary frequency was observed. It was also observed that the most intense frequency was found to be \(3024.9421 \mathrm{~cm}^{-1}\) at an intensity of \(140.2464 \mathrm{~km} / \mathrm{mol}\) in methanol and \(3088.6908\) \(\mathrm{cm}^{-1} at intensity of 77.6119 \mathrm{~km} / \mathrm{mol}\) in gas phase. The theoretical values of the open circuit voltage were found to be \(1.635 \mathrm{eV}, 1.614 \mathrm{eV}, 1.605 \mathrm{eV}, 1.576 \mathrm{eV}, 1514 \mathrm{eV}\), and \(1.445 \mathrm{eV}\) for methanol, toluene, acetone, chloroform, thiophene and the gas phase respectively. These changes in the properties of the molecule are observed due to the differences in the dielectric constants of the solvents. The results show that careful selection of the solvents can enhance the properties of the molecule for Organic solar cells (OSC)s applications.

Open Access Original Research Article

Christian Rakotonirina

A sign operator of energy, analogous to the helicity operator, but in the direction of what we call energy vector has been introduced. It is possible that there may be physical phenomena where energy vector should be considered. However, to write a wave function this energy vector needs a time vector. But, unlike the energy vector the time vector has no physical meaning yet. To make physical senses of the components of the time vector, the time dilation in special relativity has been studied and also the components of the time vector have been related to the tunneling times when an electron crosses a potential barrier. Physical results for quantum tunneling time will not be limited to this study.

Open Access Original Research Article

Kokou Prosper Semekonawo, Sié Kam

In sub-Saharan Africa the cost of transport is very expensive for the populations. As the car fleet is mainly made up of thermal cars, the high cost of transport is largely linked to the oil’s import. Faced with such a situation, it is important to find other means of transport in order to reduce the transport’s cost for the populations. One of the means of transport which seems to be an alternative solution is the solar electric car. But the difficulty for the solar electric car is its range. To improve car's range, it is necessary to analyze the performance of the car in driving conditions in order to understand the parameters that influence the range. Understanding and mastering these parameters will make it possible to make the best decisions to improve the car's range. In this article, we are interested in analyzing the energy performances of a solar electric car in Togo in order to understand the parameters that influence the car’s range. The simulation results show a considerable reduction in the car's range for high driving speeds, for excessive consumption of the auxiliary electrical circuits of the car, for driving the vehicle on a large slope, and when the car is transporting a large weight. The solar panel on the roof of the car is of great importance because it makes a significant contribution to the car’s range in sunny periods.