Open Access Original Research Article

In Situ Measurement of the Compressive Strength of Local Concrete: Correlation between Non-destructive and Destructive Tests

Saïdou Bamogo, David Y. K. Toguyeni, Fati Zoma, Mohamed Yerbanga

Physical Science International Journal, Page 1-10
DOI: 10.9734/psij/2020/v24i830205

The method used to evaluate the quality of concrete in structures includes, among other things, compressive strength testing of specimens cast on site. This method has shortcomings due to the non-uniformity in their formulation processes of the concrete studied in laboratories and that of the structure on site and the tardiness in obtaining test results. This is why the development of reliable methods of non-destructive assessment of the compressive strength of concrete in situ is essential for a better performance assessment of structures.There are a multitude of non-destructive methods, but in this article, the ultrasonic pulse velocity (UPV) and the rebound hammer (RH) are the methods used as they are easy to get manipulate, accessible and permit fast access to results. Analyses using single and multiple linear regression methods have been carried out with the results from compression tests and measurements of pulse velocity and rebound indices carried out between February and April 2018 on over 90 specimen samples in total. This resulted in correlation equations for the in-situ estimation of the compressive strength of the concrete studied.

Open Access Original Research Article

Modeling of a Condenser in Dynamic Operation Using Comsol Multiphysics Software

Jean-Louis Comlan Fannou, Kouandété Valéry Doko, Vincent Prodjinonto, Louis Lamarche, Stanislaw Kajl, Gérard Degan, Emile A. Sanya

Physical Science International Journal, Page 11-28
DOI: 10.9734/psij/2020/v24i830206

This paper is about modelling in dynamic operation the heat exchanger system using as condenser in one dimension characterized by two coaxial tubes with ribbed inner tube by using the equations of mass, momentum and energy conservation. The Comsol PDE interface is used to simulate the monophasic and biphasic flows of refrigerant. Heat transfer in water and inner wall of the condenser are modeled with two Heat Transfer Interfaces (solid, fluid) in Comsol software.

The model has been validated by comparing the numerical and experimental results obtained with the direct expansion geothermal heat pump. The analysis of the comparative results shows that the obtained model adequately fits the experimental data with an average deviation of less than 5%. Therefore, it proves that it's a good model which can be used for simulation purposes. This developed numerical model was used to simulate the superheating, condensing and subcooling phases in the condenser. Vapor quality, pressure, enthalpy of the refrigerant and water temperature are also simulated.

Open Access Original Research Article

A Review and Revisit of Newton’s Law and Gravitational Constant Derivations

Curtis J. Forsythe

Physical Science International Journal, Page 29-37
DOI: 10.9734/psij/2020/v24i830207

This paper is a review of, and complement to, my original papers previously published in Physics Essays [1] and ViXra [2]. While the derivations and results pertinent to this review are unchanged, a possible extension of the proposed model as it relates to the derivation of G and to G-experimental is explored and presented in the attached addendum.

Herein, as proposed in my previous papers, is a theoretical model of Universal Gravitation based upon hypothetical mass/energy resonance waves, the intensities of which I propose to be casually analogous with those of electromagnetic waves. Using said model, I derive the expressed Newtonian law of gravitation from which an apparent Newtonian gravitational constant factors as a combination of other physical constants, yielding a primary G-value of  6.662936 x 10-11m3/kg s2, shown by extension to yield a secondary result that correlates well with the 2018 recommended value.  A second resultant of the proposal is a demonstration that the quantum energy states of the hydrogen atom appear related to the length of these waves, shown equal to twice the ground state orbital radius in a Bohr hydrogen atom.  Additionally determined, independently of any experimental G-value, are values for the Planck mass, length, and time.

Open Access Original Research Article

Protection Value of Tropospheric Radio Refractivity over Nigerian Atmosphere

M. A. Adeniji, D. O. Olorode

Physical Science International Journal, Page 38-43
DOI: 10.9734/psij/2020/v24i830208

This study enumerates the protection values derivable from refractivity variation of the tropospheric surface in Nigeria. The investigation was conducted in four cities of Nigeria using meteorological data of 2008 procured from the centre for basic space science (cbss), university of Nigeria, (unn), Nsukka. Data were captured from four different stations: Akure, Nsukka, Minna and Sokoto using vantage pro II automatic weather station. Data measurement at half hourly interval for the whole year took place at the ground level, 0 m and 100 m altitude of the troposphere. The results of the analyzed data revealed that at 100 m altitude, Nzukka and Akure experienced better protection at refractivity value of 350 unit than Sokoto and Minna at 250 unit. At the ground level (0) m, refractivity values becomes more distinct with; Nzukka, 500 unit, Akure, 370 unit while Minna and Sokoto shared the same refractivity value of 270 unit. This trend of refractivity variation showed a decreasing order of protection against exposure to damaging effects of the cosmic and out of space radiation as we move from the south towards the northern part of the country.

Open Access Original Research Article

Reformulating Special Relativity on a Two-World Background

O. Akindele Adekugbe Joseph

Physical Science International Journal, Page 44-87
DOI: 10.9734/psij/2020/v24i830209

A new spacetime is isolated and added to the existing spacetime, yielding a pair of co-existing spacetimes, which are four-dimensional inversions of each other. The separation of the spacetimes by the special-relativistic event horizon, compels an interpretation of a pair of symmetrical worlds (or universes) in nature. Furthermore, a two-dimensional intrinsic spacetime that underlies the four-dimensional spacetime in each universe is introduced. The four-dimensional spacetime is the outward manifestation of the two-dimensional intrinsic spacetime, just as the special theory of relativity (SR) on flat four-dimensional spacetime is the outward manifestation of the intrinsic special theory of relativity (∅SR) on flat two-dimensional intrinsic spacetime in each universe. A new set of spacetime/intrinsic spacetime diagrams in the two-world picture is developed, from which intrinsic Lorentz transformation in ∅SR and Lorentz transformation in SR are derived and intrinsic Lorentz invariance and Lorentz invariance are validated in each universe. The SR remains unchanged, but the exposition of its two-world background, the isolated parallel new theory ∅SR and other isolated new features in this article, allow a broader view of SR. This article includes a new addition to the  conceptions of many worlds (or universes) in physics and it is effectively a review (in the two-world picture) of the existing geometrical representations of the Lorentz transformation (in a one-world picture).