Journal of Nature, Science & Technology (JANSET)

Yakubu Zulkifly Abbas Abdullahi Sirajo

Single bulk materials have lesser advantages compared to nano materials in the area of mechanical, electrical, dielectric, optical and thermal properties enhancement of polymer and hybrid of bio-composites. In this work, charcoal (CH), unripe plantain husk (UPH), and polycaprolactone (PCL) based microwave absorber were synthesized using both mechanical alloy and melt blend techniques, respectively. Different percentages of the prepared charcoal nanoparticles was introduced into the hybrid composites to study the effect on dielectric properties, shielding effectiveness, reflection loss and structural morphology in the frequency range of 8–12 GHz.. Findings showed that the sample with the highest amount of charcoal percentage had the best shielding effectiveness and dielectric constant. The value of dielectric constant gradually increased from 3.06 to 5.45 at the frequency range measured. The charcoal average particle size was estimated to be 21.42 nm using TEM analysis while the mean deviation of surface roughness ranged from 5.45 to 25.56 nm using atomic force microscope. The highest shielding effectiveness of the hybrid composites was obtained for the 30 wt% nano charcoal content with a value of -48.3 dB at 10 GHz. The complete dispersion and interaction of the charcoal with the PCL and UPH enhanced the dielectric constant, loss factor, hence making it potent in microwave absorption, shielding and radar applications.

https://doi.org/10.36937/janset.2021.002.001

Samaila Basant Kumar Jha

This study is devoted to investigate the importance of thermal radiation on the boundary layer over a horizontal surface considering classical constant surface boundary condition. The mathematical model consist of coupled two-dimensional partial differential equations which is transformed to the set of ordinary differential equations via the similarity transformation. The final set of dimensionless equations is solve numerically using Runge Kutta Fehlberg method (RKF45) in Maple software. The significant effect of the thermal radiation is examined using four fluids namely; water, Sulphur oxide, air and mercury whose respective Prandtl numbers are 7, 2, 0.72 and 0.044. The influence of other prominent parameters affecting the flow formation and temperature profile are demonstrated using tables and graphs. The results indicated that the thermal boundary layer thickness could be increase by reducing the Prandtl number. The results also showed that increasing the thermal radiation parameter has a positive impact on the boundary layer thickness. The heat transfer rate could be improved by increasing thermal radiation or decreased by increasing the values of the Prandtl number. Regarding the temperature gradient, an observable increasing is seen far from the flat plate with the growing of thermal radiation whereas the opposite trend is true near the plate surface.

https://doi.org/10.36937/janset.2021.002.002

Sebastiano Pennisi

In this article the known models are considered for relativistic polyatomic gases with an arbitrary number of moments, in the framework of Extended Thermodynamics. These models have the downside of being hyperbolic only in a narrow domain around equilibrium, called "hyperbolicity zone". Here it is shown how to overcome this drawback by presenting a new model which satisfies the hyperbolicity requirement for every value of the independent variables and without restrictions. The basic idea behind this new model is that hyperbolicity is limited in previous models by the approximations made there. It is here shown that hyperbolicity isn't limited also for an approximated model if terms of the same order are consistently considered, in a new way never used before in literature. To design and complete this new model, well accepted principles are used such as the "Entropy Principle" and the "Maximum Entropy Principle". Finally, new trends are analized and these considerations may require a modification of the results published so far; as a bonus, more manageable balance equations are obtained. This allows to obtain more stringent results than those so far known. For example, we will have a single quantity (the energy e) expressed by an integral and all the other constitutive functions will be expressed in terms of it and its derivatives with respect to temperature. Another useful consequence is its easier applicability to the case of diatomic and ultrarelativistic gases which are useful, at least for testing the model in simple cases.

https://doi.org/10.36937/janset.2021.002.003

Ankit Duttagupta MD Maksudul Islam Emad Rabiei Hosseinabad Muhammad Adib Uz Zaman

Corporate social responsibility (CSR) is an extension of the corporate role which encompasses the economic, legal, ethical and philanthropic responsibilities that a company must fulfill, such that it improves the overall quality of life of the community around it. Sustainable development (SD) on the other hand involves operations that have a minimal impact on the environment. However, in today’s global environment, governments around the world are implementing stricter environmental regulations and supporting higher standards of living for their citizens. This socially and environmentally conscious undertone, has made it imperative for organizations to address issues related to CSR and SD seriously and in many cases with the highest urgency. Adding to it, the views of the conscious and the well informed masses and organizations soon realize that implementing CSR and SD in their corporate strategy is not only a requirement to meet the standards set through government regulations, but it also plays a key role in maintaining the competitive advantages that an organization enjoys within its operating market segment thus safeguarding the long term economic feasibility of its various operations and overall profitability.

https://doi.org/10.36937/janset.2021.002.004

Ferhat Bülbül Erdal Sönmez Kadri Vefa Ezirmik

The play-wear tests on the strings from high carbon steel were realized by using a long necked bağlama stringed instrument. These tests were carried out by reciprocating with the finger on the sound table for different times. The stick-slip wear and striking effects were observed on the strings by AFM. A noticeable increase was detected in the values of surface roughness obtained from Do, Fa, and Si pitch-strings and the chest region-string depending on the beat amount. Hence, it attracts attention that the roughness values decrease while it is passed from 1000 to 3000 beats and from Do pitch to Fa concerning beat amount and pitches. However, such an increase was not detected in the Si pitch-string and the chest region-string, and whilst passing from 3000 to 6000 beats, on the contrary, the average surface roughness values showed a tendency to increase.

https://doi.org/10.36937/janset.2021.002.005