Journal Papers (30) Details

1
Low-Cost Jute-Cotton and Glass Fibre Reinforced Textile Composite Sheet
,
Md. Moslem Uddin1, Rezaul Karim2, M A Kaysar1, Md. Anisur Rahman Dayan1, and Kazi Asraful Islam2*
1Textile Physics Division, Bangladesh Jute Research Institute, Dhaka-1707, Bangladesh; and 2Department of Textile Engineering, Sonargaon University, Dhaka-1212, Bangladesh
*Correspondence: kazinooman@gmail.com
Composite material is a single structure composed of two or more materials with identifiable interfaces at multi-scales to get properties that are superior to those of its constituents. Composites are designed to get unique mechanical properties and superior performance characteristics that are not possible with any of its component material alone. An experimental work was done at Textile Physics Division of BJRI, Bangladesh, in 2019 for the manufacture of jute, cotton and glass fire reinforced composite corrugated sheet suitable for roofing in poultry and rural housing. For the investigation jute, cotton and glass fibre were used like as reinforcing material and polyester resin were used like as matrix material. This paper reports the findings of an experimental investigation conducted on the engineering properties of jute, cotton and glass fibre reinforced composite corrugated sheet. Different fabric design and volume fractions were used as reinforcement for corrugated sheet to determine the physical, mechanical and thermal properties of the composite. The results of this investigation have showed the feasibility of the use of jute fibre for producing low cost housing materials. |
||||||

2
Fitting ARIMA Model and Forecasting for the Tea Production, and Internal Consumption of Tea (Per year) and Export of Tea
,
Md. Aliul Islam1*, Mst. Sharmin Akter Sumy1, Md. Alhaz Uddin2, and Md. Sazzad Hossain1
1Dept. of Statistics, Islamic University, Jhenidah-Kushtia, Bangladesh; and 2Dept. of Statistics, University of Rajshahi, Rajshahi, Bangladesh.
*Correspondence: aliulstatiu2010@gmail.com
Every year, in Bangladesh the production has increased by 1.84 % and contributes 1.37 in export in the word tea trade and earns nearing 1775 million Taka. The internal consumers of the country are presently consuming about 98% of its produce. The consumption is increasing day by day mainly due to the rapid increase in population. This study considered the published secondary data of yearly tea production in Bangladesh over the period 1990 to 2015 by the Bangladesh Tea Board. We are forecasting the production of tea and internal consumption of tea by using Auto-Regressive Integrated Moving Average (ARIMA) for the next 5 years. Run test, Jarque and Bera test criteria are used for the adequacy of the fitted model which followed by the residual analysis. The comparison between the original series and forecasted series are showing the same trends which indicate the fitted model is statistically well and appropriate for the forecast the productions of tea in Bangladesh. |
||||||

3
First Principles Study of Structural, Elastic, Electronic and Optical Features of the Non-centrosymmetric Superconductors SrMGe3 (Where M= Ir, Pt, and Pd)
,
Mst. Jannatul Naefa1, and Md. Atikur Rahman2*
1&2Department of Physics, Pabna University of Science and Technology, Pabna-6600, Bangladesh.
*Correspondence: atik0707phy@gmail.com (Md. Atikur Rahman, Assistant Professor, Dept. of Physics, Pabna University of Science and Technology, Pabna, Bangladesh).
BaNiSn3-type superconductors SrIrGe3, SrPdGe3 and SrPtGe3 have the critical temperature of 1.80 K, 1.49K and 1.0K respectively have been reported recently. Employing the first-principles method based on the density function theory, we have examined the physical properties including structural, elastic, electronic and optical phenomena of all these structures. For all the phases our optimized lattice parameters are well accord to the experimental lattice parameters. The positive elastic constants of these compounds revealed that these superconductors possess the mechanical stability in nature. The values of Pugh’s ratio and Poisson’s ratio ensured the brittle manner of these compounds and anisotropic behavior is ensured by the values of anisotropy factor. The soft nature of all compounds is confirmed by the bulk modulus analysis. The values of Vickers hardness indicate that the rigidity decreased in the order of SrIrGe3>SrPtGe3>SrPdGe3. The overlapping of the conduction band and valence band at Fermi level indicates the zero band gaps and metallic nature of SrIrGe3, SrPdGe3 and SrPtGe3. The chief contribution around the Fermi level arises from Ir-5d, Ge-4s, 4p states for SrIrGe3 and Ge-4s, 4p states for SrPdGe3 and Pt-5d, Ge-4s, 4p for SrPtGe3 compound. The study of DOS, Mulliken atomic populations and charge density ensured the existing of complex bonding in SrIrGe3, SrPdGe3 and SrPtGe3 with ionic, covalent and metallic characteristics. The analysis of the dielectric function also ensured the metallic behavior of all these compounds. |
||||||

4
Influence of High Power Nd: YAG Laser on Hardness and Surface Properties of Zirconium Silicate
,
Alaa Salahaldin Awadala1, Ahmed Elhassan Elfaky1, and Ali A. S. Marouf2*
1Department of Physics, College of Science, Sudan University of Science and Technology, Khartoum, Sudan; 2Department of Laser Engineering and Industrial Applications, Institute of Laser, Sudan University of Science and Technology, Khartoum, Sudan.
*Correspondence: marouf.44@gmail.com (Ali A. S. Marouf, Associate Professor, Department of Laser Engineering and Industrial Applications, Sudan University of Science and Technology, Sudan).
Different parameters like irradiated area, irradiation time, laser wavelength, pulse energy, and the nature of the irradiated material determine largely the effect of the laser-matter interaction. In this, study the influence of high power Nd: YAG laser irradiation on the hardness and surface properties of zirconium silicate (ZrSiO4) ceramics was investigated. Specimens of zirconium ceramic pieces were divided into four samples depend on irradiation duration as follows: one reference sample and three samples treated with Nd: YAG laser at irradiation times vary from 3 to 5 minutes. The irradiation was done with 60 W output power. The hardness and tensile strength were determined and the optical properties were characterized by UV-vis spectroscopy, also EDX spectra were carried out. The obtained results revealed that high power (60 W) Nd: YAG laser provides higher hardness compared to the reference sample surface. Increasing irradiation time resulted in the higher hardness of the ceramic surfaces. EDX results showed that laser irradiation does not change the chemical surface composition of ceramics. Moreover, increase in transmittance of the irradiated zirconium silicate in the visible and near-infrared range was also found using UV-vis spectroscopy. |
||||||

5
MHD Free Convective Heat Transfer in a Triangular Enclosure Filled with Copper-Water Nanofluid
,
Tarikul Islam1*, Nahida Akter2, and Nusrat Jahan3
1&2Department of Mathematics, Bangabandhu Sheikh Mujibur Rahman Science and Technology University, Gopalganj, Bangladesh; 3Department of Science and Humanity, Bangladesh Army International University of Science and Technology, Cumilla, Bangladesh.
*Correspondence: tarikulamath@gmail.com
Two-dimensional time independent free convective flow and temperature flow into a right-angled triangle shape cavity charged by Cu-H2O nanofluid has been performed. The horizontal side of the enclosure is warmed uniformly T=Th whilst the standing wall is cooled at low temperature T-Tc and hypotenuse of the triangular is insulated. The dimensionless non-linear governing PDEs have been solved numerically employing the robust PDE solver the Galerkin weighted residual finite element technique. An excellent agreement is founded between the previous, and present studies. The outcomes are displayed through streamline contours, isotherm contours, and local and average Nusselt number for buoyancy-driven parameter Rayleigh number, Hartmann number, and nanoparticles volume fraction. The outcomes show that the temperature flow value significantly changes for the increases of Rayleigh number, Hartmann number , and nanoparticles volume fraction. Average Nusselt number is increased for the composition of nanoparticles whereas diminishes with the increase of Hartmann number. |
||||||

6
A Critical Exploration of Some Fundamental Terms and Terminologies in Statistics
,
M A Jalil1 and Md. Jamil Hasan Karami 2*
1&2Department of Statistics, University of Dhaka, Dhaka, Bangladesh.
*Correspondence: karami.stat@du.ac.bd (Dr. Md. Jamil Hasan Karami, Associate Professor, Department of Statistics, University of Dhaka, Dhaka, Bangladesh).
This article focuses on the understanding of definitions of several widely used statistical terms such as degrees of freedom, locations, range, dispersion, grouped and ungrouped data. The terms have been redefined along with examples so that they stand alone to express their meaning. In this article, a new term ‘the smallest unit’ in a statistical sense has been defined and illustrated in some instances. It is also indicated how statisticians or practitioners of statistics are using it knowingly or unknowingly. We have mentioned the application of the smallest unit in the classification of data. Moreover, the concept of the smallest unit has been synced with the definition of sample range so that the range can cover the entire space of values. Therefore, the proposed sample range can now better approximate the population range. We have shown that researchers can end up with misleading result if they treat a dataset as an ungrouped data when it is truly a grouped data. This has been discussed in the computation of different percentiles. Moreover, the crux of the definition of degrees of freedom and dispersion has been pointed out which has helped repelled the confusion behind these terms. We have shown how the concept of linearly independent pieces of information is related to the definition of degrees of freedom. We have also emphasized not to mix the definition of standard deviation and/or variance with the whole concept of dispersion because the former is merely a single measure among many measures of the latter. |
||||||

7
First Principles Study on the Structural, Elastic, Electronic and Optical Properties of Cubic ‘Half-Heusler’ Alloy RuVAs Under Pressure
,
Farhana Mostari1, Md. Atikur Rahman2*, Rukayia Khatun3
1,2&3Department of Physics, Pabna University of Science and Technology, Pabna-6600, Bangladesh.
*Correspondence: atik0707phy@gmail.com (Md. Atikur Rahman, Assistant Professor, Department of Physics, Pabna University of Science and Technology, Pabna, Bangladesh).
The pressure effect (0 to 40 GPa) on the structural, elastic, electronic and optical properties of half-metallic compound RuVAs has been investigated employing the DFT based on the first-principles method. The CASTEP computer code is used for this investigation. The calculated lattice parameter show slide deviation from the synthesized and other theoretical data. The normalized lattice parameter and volume are decreased with increasing pressure. The zero pressure elastic constants and also the pressure-dependent elastic constants are positive up to 40 GPa and satisfy the Born stability condition which ensured that the compound RuVAs is stable in nature. At zero pressure, the electronic band gap of 0.159 eV is observed from the band structure calculations which ensured the semimetallic nature of RuVAs. No band gap is observed in the electronic band structure at 40 GPa which indicates the occurrence of phase transition of compound RuVAs at this pressure. We have calculated the value of bulk modulus B, shear modulus G, Young’s modulus E, Pugh ratio B/G, Poisson’s ratio ν and anisotropy factor A of this compound by using the Voigt-Reuss-Hill (VRH) averaging scheme under pressure. The bulk modulus shows a linear response to pressure so that the hardness of this material is increased with increasing pressure. Furthermore the optical properties such as reflectivity, absorptivity, conductivity, dielectric constant, refractive index and loss function of RuVAs were evaluated and discussed under pressure up to 40 GPa. |
||||||

8
Prediction of Banking Sectors Financial Data of Dhaka Stock Exchange Using Autoregressive Integrated Moving Average (ARIMA) Approach
,
Md. Farhad Hossain1*, Dulal Chandra Nandi1, and Kazi Mohammed Kamal Uddin2
1Department of Statistics, Comilla University, Cumilla, Bangladesh; and 2Department of Economics, Comilla University, Cumilla, Bangladesh.
*Correspondence: farhad390ju@gmail.com (Md. Farhad Hossain, Assistant Professor, Department of Statistics, Comilla University, Cumilla, Bangladesh).
This paper investigates the predictability with the banking sector data of the Dhaka Stock Exchange (DSE) by using the Autoregressive Integrated Moving Average (ARIMA) process. Through different formal tests on the data set, the best-fitted model selected was ARIMA (0,2,1) for the data series. This study was select five banks from DSE such as Al-Arafah bank limited, EXIM bank limited, Islami bank limited, National bank limited, and one bank limited and use these data to train the model and checks the predictive power of the model. Only analyzed results of Al-Arafah bank limited are presented in this paper because the same results have been produced for other remaining companies. The obtained results show that all the companies closing stock prices are non-stationary. It is also found that the original value curve and the predicted value curve are very much identical. So, the fitted model is performed better. For the validity of the model, the root means squared error (RMSE), mean absolute error (MAE) and mean absolute percentage error (MAPE) were checked. |
||||||

9
Synthesis, Characterization and Pressure Effect on Structural and Mechanical Properties of MgBi2O6: Solid-State Route and DFT Study
,
Md. Atikur Rahman1*, Md. Afjalur Rahman2, and Abdur Razzaque Sarker3
1,2Department of Physics, Pabna University of Science and Technology, Pabna-6600, Bangladesh; and 3Department of Physics, Rajshahi University, Rajshahi-6205, Bangladesh.
*Correspondence: atik0707phy@gmail.com (Md. Atikur Rahman, Assistant Professor, Department of Physics, Pabna University of Science and Technology, Pabna, Bangladesh).
Here we have prepared good quality crystalline sample MgBi2O6 employing the solid state reaction technique. The synthesized material was characterized by XRD and SEM (scanning electron microscopy). The structural study confirmed that MgBi2O6 possesses tetragonal crystal configuration (JCPDS PDF#, No. 86-2492) with outstanding crystallinity and a grain size between 200 to 350 nm. The temperature dependence electrical resistivity and conductivity were measured by two probe methods and ensured the semiconducting nature of this material. Using the impedance analyzer and UV-visible spectrophotometer we studied the experimental electronic and optical properties of this material. To explore the hypothetical features of MgBi2O6 we have used first principles methods which depend on CASTEP code. The band structure analysis also ensured the semiconducting nature of MgBi2O6 with small band gap of 0.12 eV. The semiconducting behavior of MgBi2O6 with band gap of 0.12 eV was also observed by the band structure analysis. The Born’s stability criteria were fulfilled by the investigated elastic constants and ensured the stable nature of MgBi2O6. The response of structural and mechanical properties with pressure of MgBi2O6 was discussed in details. We have also studied the hypothetical optical properties of MgBi2O6 by CASTEP code. |
||||||

10
The Metric of Space-Time Curvature in a Weak Gravitational Field and it’s Consequence in Newtonian Approximation
,
Md. Ashik Iqbal1*, Al Mahmud Al Mamun2, Md. Rasel Hossain3, and Md. Kamrul Hassan2
1Dept. of Applied Mathematics, University of Rajshahi, Rajshahi, Bangladesh, 2Dept. of Computer Science and Engineering, Islamic University, Bangladesh; and 3Dept. of Statistics, Noakhali Science and Technology University, Noakhali, Bangladesh.
*Correspondence: ashikiqbalmath@gmail.com (Md. Ashik Iqbal, Dept. of Applied Mathematics, University of Rajshahi, Rajshahi, Bangladesh).
In Newtonian mechanics, space and time are separate but in General Relativity is unified. It is considered that the space in the weak-field approximation is quasi-static and it arises from a perfect field whose particles have very small velocity in comparison to light velocity in this coordinate system and the metric is a gravitational potential tensor of rank two which implies the field of empty space. If each point of an area in N-dimensional space there existed a corresponding definite tensor, where the components of the tensor are the function of space and space acts as the strong or weak gravitational field. |
||||||

11
Efficient Water Management and Selection of Cooling System for Future NPP in Bangladesh
,
Md. Rakibul Hasan1*, K M Rezaur Rahman2, Md. Bodhroddoza Shohag1, and M. Mezbah Uddin1
1Center for Research Reactor, Atomic Energy Research Establishment, Ganakbari, Savar, Dhaka, Bangladesh and 2International Affairs Division, Bangladesh Atomic Energy Commission, E-12/A, Agargaon, Sher-e-Bangla Nagar, Dhaka, Bangladesh.
*Correspondence: rakibmist@gmail.com (Md. Rakibul Hasan, Senior Engineer, Center for Research Reactor, Atomic Energy Research Establishment, Ganakbari, Savar, Dhaka, Bangladesh).
Water withdrawal today presents a vital issue for Bangladesh to build a new nuclear power plant (NPP) as the country has a deficit in its water resources. It is an issue that may create conflict among the socio-economic activities that require and depend on the water like agriculture that mostly depends on river and ground water. Very recently nuclear power has come into focus during debates on energy generation, often in relation to wider issues such as global warming and climate change. According to Power System Master Plan (PSMP) 2016 of the Government of Bangladesh, it is estimated that a capacity of 7200 MWe of electricity may be generated from nuclear power by 2041 (PSMP, 2016). The government of Bangladesh has already started the construction work of 2400 MWe Rooppur NPP and planning to construct more units of NPPs in the future to fulfill the planning of PSMP 2016. Usually, water is used as a coolant for most of the commercial NPP designed in the present world. In this paper, a study has been performed about the estimation of both the needs for cooling water and other essential systems for a future NPP in Bangladesh using IAEA’s Water Management Program (WAMP). Moreover, the selection of cooling systems by evaluating three different criteria: water resource, environment, and economics, has also been performed during this study. |
||||||

12
An Execution of a Mathematical Example Using Euler’s Phi-Function in Hill Chiper Cryptosystem
,
Mohiuddin Ahmed1* and Md. Ashik Iqbal1
1Faculty Member in Mathematics, Department of Computer Science and Engineering, North Western University (NWU), Khulna, Bangladesh.
*Correspondence: mohiuddina6@gmail.com (Mohiuddin Ahmed, Faculty Member in Mathematics, Department of Computer Science and Engineering, NWU, Khulna, Bangladesh).
In this article, we have explained the RSA public-key cryptosystem initiate by Rivest and Hill Chiper cryptosystem initiate by Lester. Hill for coding and decoding the text. To explain these we apply the Euler-phi function, congruence, and simple Matrix Application in cryptography to decode and encode the message. In our analyses, we were collaborated two cryptosystems which is more assured than standard cryptographic process such as Ceaser cipher. We apply both secret-key cryptography and public-key cryptography which differ from standard cryptography. In our presentation, we use two keys for coding and two for decoding. |
||||||

13
Cooperative Spectrum Sensing with Selection Diversity Reception in Cognitive Radio
,
Md. Farukuzzaman Khan1 and Mohammad Alamgir Hossain2*
1&2Department of Computer Science and Engineering, Islamic University (IU), Jhenidah-Kushtia, Bangladesh.
*Correspondence: alamgir@cse.iu.ac.bd (Mohammad Alamgir Hossain, Assistant Professor, Department of Computer Science and Engineering, IU, Jhenidah-Kushtia, Bangladesh).
Spectrum sensing is the key component of cognitive radio technology. But, detection is compromised when a user reports shadowing or fading consequences. In such instances, the customer cannot apprehend between an unexploited band and a profound fade. Hence, communal spectrum sensing is suggested to optimize sensing overall performance. We recognition performance of communal Spectrum Sensing with Selection Diversity Reception in Cognitive Radio. This study presents a simulation evaluation of choice diversity Reception based totally on fusion rule. Fusion rule is finished at the fusion centre (FC) to make the very last selection about the presence of PU. This leads that spectrum sensing is enthusiastically in the presence of Rayleigh. |
||||||

14
Low-Cost Jute-Cotton and Glass Fibre Reinforced Textile Composite Sheet
,
Md. Moslem Uddin1, Rezaul Karim2, M A Kaysar1, Md. Anisur Rahman Dayan1, and Kazi Asraful Islam2*
1Textile Physics Division, Bangladesh Jute Research Institute, Dhaka-1707, Bangladesh; and 2Department of Textile Engineering, Sonargaon University, Dhaka-1212, Bangladesh
*Correspondence: kazinooman@gmail.com
Composite material is a single structure composed of two or more materials with identifiable interfaces at multi-scales to get properties that are superior to those of its constituents. Composites are designed to get unique mechanical properties and superior performance characteristics that are not possible with any of its component material alone. An experimental work was done at Textile Physics Division of BJRI, Bangladesh, in 2019 for the manufacture of jute, cotton and glass fire reinforced composite corrugated sheet suitable for roofing in poultry and rural housing. For the investigation jute, cotton and glass fibre were used like as reinforcing material and polyester resin were used like as matrix material. This paper reports the findings of an experimental investigation conducted on the engineering properties of jute, cotton and glass fibre reinforced composite corrugated sheet. Different fabric design and volume fractions were used as reinforcement for corrugated sheet to determine the physical, mechanical and thermal properties of the composite. The results of this investigation have showed the feasibility of the use of jute fibre for producing low cost housing materials. |
||||||

15
Fitting ARIMA Model and Forecasting for the Tea Production, and Internal Consumption of Tea (Per year) and Export of Tea
,
Md. Aliul Islam1*, Mst. Sharmin Akter Sumy1, Md. Alhaz Uddin2, and Md. Sazzad Hossain1
1Dept. of Statistics, Islamic University, Jhenidah-Kushtia, Bangladesh; and 2Dept. of Statistics, University of Rajshahi, Rajshahi, Bangladesh.
*Correspondence: aliulstatiu2010@gmail.com
Every year, in Bangladesh the production has increased by 1.84 % and contributes 1.37 in export in the word tea trade and earns nearing 1775 million Taka. The internal consumers of the country are presently consuming about 98% of its produce. The consumption is increasing day by day mainly due to the rapid increase in population. This study considered the published secondary data of yearly tea production in Bangladesh over the period 1990 to 2015 by the Bangladesh Tea Board. We are forecasting the production of tea and internal consumption of tea by using Auto-Regressive Integrated Moving Average (ARIMA) for the next 5 years. Run test, Jarque and Bera test criteria are used for the adequacy of the fitted model which followed by the residual analysis. The comparison between the original series and forecasted series are showing the same trends which indicate the fitted model is statistically well and appropriate for the forecast the productions of tea in Bangladesh. |
||||||

16
First Principles Study of Structural, Elastic, Electronic and Optical Features of the Non-centrosymmetric Superconductors SrMGe3 (Where M= Ir, Pt, and Pd)
,
Mst. Jannatul Naefa1, and Md. Atikur Rahman2*
1&2Department of Physics, Pabna University of Science and Technology, Pabna-6600, Bangladesh.
*Correspondence: atik0707phy@gmail.com (Md. Atikur Rahman, Assistant Professor, Dept. of Physics, Pabna University of Science and Technology, Pabna, Bangladesh).
BaNiSn3-type superconductors SrIrGe3, SrPdGe3 and SrPtGe3 have the critical temperature of 1.80 K, 1.49K and 1.0K respectively have been reported recently. Employing the first-principles method based on the density function theory, we have examined the physical properties including structural, elastic, electronic and optical phenomena of all these structures. For all the phases our optimized lattice parameters are well accord to the experimental lattice parameters. The positive elastic constants of these compounds revealed that these superconductors possess the mechanical stability in nature. The values of Pugh’s ratio and Poisson’s ratio ensured the brittle manner of these compounds and anisotropic behavior is ensured by the values of anisotropy factor. The soft nature of all compounds is confirmed by the bulk modulus analysis. The values of Vickers hardness indicate that the rigidity decreased in the order of SrIrGe3>SrPtGe3>SrPdGe3. The overlapping of the conduction band and valence band at Fermi level indicates the zero band gaps and metallic nature of SrIrGe3, SrPdGe3 and SrPtGe3. The chief contribution around the Fermi level arises from Ir-5d, Ge-4s, 4p states for SrIrGe3 and Ge-4s, 4p states for SrPdGe3 and Pt-5d, Ge-4s, 4p for SrPtGe3 compound. The study of DOS, Mulliken atomic populations and charge density ensured the existing of complex bonding in SrIrGe3, SrPdGe3 and SrPtGe3 with ionic, covalent and metallic characteristics. The analysis of the dielectric function also ensured the metallic behavior of all these compounds. |
||||||

17
Influence of High Power Nd: YAG Laser on Hardness and Surface Properties of Zirconium Silicate
,
Alaa Salahaldin Awadala1, Ahmed Elhassan Elfaky1, and Ali A. S. Marouf2*
1Department of Physics, College of Science, Sudan University of Science and Technology, Khartoum, Sudan; 2Department of Laser Engineering and Industrial Applications, Institute of Laser, Sudan University of Science and Technology, Khartoum, Sudan.
*Correspondence: marouf.44@gmail.com (Ali A. S. Marouf, Associate Professor, Department of Laser Engineering and Industrial Applications, Sudan University of Science and Technology, Sudan).
Different parameters like irradiated area, irradiation time, laser wavelength, pulse energy, and the nature of the irradiated material determine largely the effect of the laser-matter interaction. In this, study the influence of high power Nd: YAG laser irradiation on the hardness and surface properties of zirconium silicate (ZrSiO4) ceramics was investigated. Specimens of zirconium ceramic pieces were divided into four samples depend on irradiation duration as follows: one reference sample and three samples treated with Nd: YAG laser at irradiation times vary from 3 to 5 minutes. The irradiation was done with 60 W output power. The hardness and tensile strength were determined and the optical properties were characterized by UV-vis spectroscopy, also EDX spectra were carried out. The obtained results revealed that high power (60 W) Nd: YAG laser provides higher hardness compared to the reference sample surface. Increasing irradiation time resulted in the higher hardness of the ceramic surfaces. EDX results showed that laser irradiation does not change the chemical surface composition of ceramics. Moreover, increase in transmittance of the irradiated zirconium silicate in the visible and near-infrared range was also found using UV-vis spectroscopy. |
||||||

18
MHD Free Convective Heat Transfer in a Triangular Enclosure Filled with Copper-Water Nanofluid
,
Tarikul Islam1*, Nahida Akter2, and Nusrat Jahan3
1&2Department of Mathematics, Bangabandhu Sheikh Mujibur Rahman Science and Technology University, Gopalganj, Bangladesh; 3Department of Science and Humanity, Bangladesh Army International University of Science and Technology, Cumilla, Bangladesh.
*Correspondence: tarikulamath@gmail.com
Two-dimensional time independent free convective flow and temperature flow into a right-angled triangle shape cavity charged by Cu-H2O nanofluid has been performed. The horizontal side of the enclosure is warmed uniformly T=Th whilst the standing wall is cooled at low temperature T-Tc and hypotenuse of the triangular is insulated. The dimensionless non-linear governing PDEs have been solved numerically employing the robust PDE solver the Galerkin weighted residual finite element technique. An excellent agreement is founded between the previous, and present studies. The outcomes are displayed through streamline contours, isotherm contours, and local and average Nusselt number for buoyancy-driven parameter Rayleigh number, Hartmann number, and nanoparticles volume fraction. The outcomes show that the temperature flow value significantly changes for the increases of Rayleigh number, Hartmann number , and nanoparticles volume fraction. Average Nusselt number is increased for the composition of nanoparticles whereas diminishes with the increase of Hartmann number. |
||||||

19
A Critical Exploration of Some Fundamental Terms and Terminologies in Statistics
,
M A Jalil1 and Md. Jamil Hasan Karami 2*
1&2Department of Statistics, University of Dhaka, Dhaka, Bangladesh.
*Correspondence: karami.stat@du.ac.bd (Dr. Md. Jamil Hasan Karami, Associate Professor, Department of Statistics, University of Dhaka, Dhaka, Bangladesh).
This article focuses on the understanding of definitions of several widely used statistical terms such as degrees of freedom, locations, range, dispersion, grouped and ungrouped data. The terms have been redefined along with examples so that they stand alone to express their meaning. In this article, a new term ‘the smallest unit’ in a statistical sense has been defined and illustrated in some instances. It is also indicated how statisticians or practitioners of statistics are using it knowingly or unknowingly. We have mentioned the application of the smallest unit in the classification of data. Moreover, the concept of the smallest unit has been synced with the definition of sample range so that the range can cover the entire space of values. Therefore, the proposed sample range can now better approximate the population range. We have shown that researchers can end up with misleading result if they treat a dataset as an ungrouped data when it is truly a grouped data. This has been discussed in the computation of different percentiles. Moreover, the crux of the definition of degrees of freedom and dispersion has been pointed out which has helped repelled the confusion behind these terms. We have shown how the concept of linearly independent pieces of information is related to the definition of degrees of freedom. We have also emphasized not to mix the definition of standard deviation and/or variance with the whole concept of dispersion because the former is merely a single measure among many measures of the latter. |
||||||

20
First Principles Study on the Structural, Elastic, Electronic and Optical Properties of Cubic ‘Half-Heusler’ Alloy RuVAs Under Pressure
,
Farhana Mostari1, Md. Atikur Rahman2*, Rukayia Khatun3
1,2&3Department of Physics, Pabna University of Science and Technology, Pabna-6600, Bangladesh.
*Correspondence: atik0707phy@gmail.com (Md. Atikur Rahman, Assistant Professor, Department of Physics, Pabna University of Science and Technology, Pabna, Bangladesh).
The pressure effect (0 to 40 GPa) on the structural, elastic, electronic and optical properties of half-metallic compound RuVAs has been investigated employing the DFT based on the first-principles method. The CASTEP computer code is used for this investigation. The calculated lattice parameter show slide deviation from the synthesized and other theoretical data. The normalized lattice parameter and volume are decreased with increasing pressure. The zero pressure elastic constants and also the pressure-dependent elastic constants are positive up to 40 GPa and satisfy the Born stability condition which ensured that the compound RuVAs is stable in nature. At zero pressure, the electronic band gap of 0.159 eV is observed from the band structure calculations which ensured the semimetallic nature of RuVAs. No band gap is observed in the electronic band structure at 40 GPa which indicates the occurrence of phase transition of compound RuVAs at this pressure. We have calculated the value of bulk modulus B, shear modulus G, Young’s modulus E, Pugh ratio B/G, Poisson’s ratio ν and anisotropy factor A of this compound by using the Voigt-Reuss-Hill (VRH) averaging scheme under pressure. The bulk modulus shows a linear response to pressure so that the hardness of this material is increased with increasing pressure. Furthermore the optical properties such as reflectivity, absorptivity, conductivity, dielectric constant, refractive index and loss function of RuVAs were evaluated and discussed under pressure up to 40 GPa. |
||||||

21
Prediction of Banking Sectors Financial Data of Dhaka Stock Exchange Using Autoregressive Integrated Moving Average (ARIMA) Approach
,
Md. Farhad Hossain1*, Dulal Chandra Nandi1, and Kazi Mohammed Kamal Uddin2
1Department of Statistics, Comilla University, Cumilla, Bangladesh; and 2Department of Economics, Comilla University, Cumilla, Bangladesh.
*Correspondence: farhad390ju@gmail.com (Md. Farhad Hossain, Assistant Professor, Department of Statistics, Comilla University, Cumilla, Bangladesh).
This paper investigates the predictability with the banking sector data of the Dhaka Stock Exchange (DSE) by using the Autoregressive Integrated Moving Average (ARIMA) process. Through different formal tests on the data set, the best-fitted model selected was ARIMA (0,2,1) for the data series. This study was select five banks from DSE such as Al-Arafah bank limited, EXIM bank limited, Islami bank limited, National bank limited, and one bank limited and use these data to train the model and checks the predictive power of the model. Only analyzed results of Al-Arafah bank limited are presented in this paper because the same results have been produced for other remaining companies. The obtained results show that all the companies closing stock prices are non-stationary. It is also found that the original value curve and the predicted value curve are very much identical. So, the fitted model is performed better. For the validity of the model, the root means squared error (RMSE), mean absolute error (MAE) and mean absolute percentage error (MAPE) were checked. |
||||||

22
Synthesis, Characterization and Pressure Effect on Structural and Mechanical Properties of MgBi2O6: Solid-State Route and DFT Study
,
Md. Atikur Rahman1*, Md. Afjalur Rahman2, and Abdur Razzaque Sarker3
1,2Department of Physics, Pabna University of Science and Technology, Pabna-6600, Bangladesh; and 3Department of Physics, Rajshahi University, Rajshahi-6205, Bangladesh.
*Correspondence: atik0707phy@gmail.com (Md. Atikur Rahman, Assistant Professor, Department of Physics, Pabna University of Science and Technology, Pabna, Bangladesh).
Here we have prepared good quality crystalline sample MgBi2O6 employing the solid state reaction technique. The synthesized material was characterized by XRD and SEM (scanning electron microscopy). The structural study confirmed that MgBi2O6 possesses tetragonal crystal configuration (JCPDS PDF#, No. 86-2492) with outstanding crystallinity and a grain size between 200 to 350 nm. The temperature dependence electrical resistivity and conductivity were measured by two probe methods and ensured the semiconducting nature of this material. Using the impedance analyzer and UV-visible spectrophotometer we studied the experimental electronic and optical properties of this material. To explore the hypothetical features of MgBi2O6 we have used first principles methods which depend on CASTEP code. The band structure analysis also ensured the semiconducting nature of MgBi2O6 with small band gap of 0.12 eV. The semiconducting behavior of MgBi2O6 with band gap of 0.12 eV was also observed by the band structure analysis. The Born’s stability criteria were fulfilled by the investigated elastic constants and ensured the stable nature of MgBi2O6. The response of structural and mechanical properties with pressure of MgBi2O6 was discussed in details. We have also studied the hypothetical optical properties of MgBi2O6 by CASTEP code. |
||||||

23
The Metric of Space-Time Curvature in a Weak Gravitational Field and it’s Consequence in Newtonian Approximation
,
Md. Ashik Iqbal1*, Al Mahmud Al Mamun2, Md. Rasel Hossain3, and Md. Kamrul Hassan2
1Dept. of Applied Mathematics, University of Rajshahi, Rajshahi, Bangladesh, 2Dept. of Computer Science and Engineering, Islamic University, Bangladesh; and 3Dept. of Statistics, Noakhali Science and Technology University, Noakhali, Bangladesh.
*Correspondence: ashikiqbalmath@gmail.com (Md. Ashik Iqbal, Dept. of Applied Mathematics, University of Rajshahi, Rajshahi, Bangladesh).
In Newtonian mechanics, space and time are separate but in General Relativity is unified. It is considered that the space in the weak-field approximation is quasi-static and it arises from a perfect field whose particles have very small velocity in comparison to light velocity in this coordinate system and the metric is a gravitational potential tensor of rank two which implies the field of empty space. If each point of an area in N-dimensional space there existed a corresponding definite tensor, where the components of the tensor are the function of space and space acts as the strong or weak gravitational field. |
||||||

24
Efficient Water Management and Selection of Cooling System for Future NPP in Bangladesh
,
Md. Rakibul Hasan1*, K M Rezaur Rahman2, Md. Bodhroddoza Shohag1, and M. Mezbah Uddin1
1Center for Research Reactor, Atomic Energy Research Establishment, Ganakbari, Savar, Dhaka, Bangladesh and 2International Affairs Division, Bangladesh Atomic Energy Commission, E-12/A, Agargaon, Sher-e-Bangla Nagar, Dhaka, Bangladesh.
*Correspondence: rakibmist@gmail.com (Md. Rakibul Hasan, Senior Engineer, Center for Research Reactor, Atomic Energy Research Establishment, Ganakbari, Savar, Dhaka, Bangladesh).
Water withdrawal today presents a vital issue for Bangladesh to build a new nuclear power plant (NPP) as the country has a deficit in its water resources. It is an issue that may create conflict among the socio-economic activities that require and depend on the water like agriculture that mostly depends on river and ground water. Very recently nuclear power has come into focus during debates on energy generation, often in relation to wider issues such as global warming and climate change. According to Power System Master Plan (PSMP) 2016 of the Government of Bangladesh, it is estimated that a capacity of 7200 MWe of electricity may be generated from nuclear power by 2041 (PSMP, 2016). The government of Bangladesh has already started the construction work of 2400 MWe Rooppur NPP and planning to construct more units of NPPs in the future to fulfill the planning of PSMP 2016. Usually, water is used as a coolant for most of the commercial NPP designed in the present world. In this paper, a study has been performed about the estimation of both the needs for cooling water and other essential systems for a future NPP in Bangladesh using IAEA’s Water Management Program (WAMP). Moreover, the selection of cooling systems by evaluating three different criteria: water resource, environment, and economics, has also been performed during this study. |
||||||

25
An Execution of a Mathematical Example Using Euler’s Phi-Function in Hill Chiper Cryptosystem
,
Mohiuddin Ahmed1* and Md. Ashik Iqbal1
1Faculty Member in Mathematics, Department of Computer Science and Engineering, North Western University (NWU), Khulna, Bangladesh.
*Correspondence: mohiuddina6@gmail.com (Mohiuddin Ahmed, Faculty Member in Mathematics, Department of Computer Science and Engineering, NWU, Khulna, Bangladesh).
In this article, we have explained the RSA public-key cryptosystem initiate by Rivest and Hill Chiper cryptosystem initiate by Lester. Hill for coding and decoding the text. To explain these we apply the Euler-phi function, congruence, and simple Matrix Application in cryptography to decode and encode the message. In our analyses, we were collaborated two cryptosystems which is more assured than standard cryptographic process such as Ceaser cipher. We apply both secret-key cryptography and public-key cryptography which differ from standard cryptography. In our presentation, we use two keys for coding and two for decoding. |
||||||

26
Cooperative Spectrum Sensing with Selection Diversity Reception in Cognitive Radio
,
Md. Farukuzzaman Khan1 and Mohammad Alamgir Hossain2*
1&2Department of Computer Science and Engineering, Islamic University (IU), Jhenidah-Kushtia, Bangladesh.
*Correspondence: alamgir@cse.iu.ac.bd (Mohammad Alamgir Hossain, Assistant Professor, Department of Computer Science and Engineering, IU, Jhenidah-Kushtia, Bangladesh).
Spectrum sensing is the key component of cognitive radio technology. But, detection is compromised when a user reports shadowing or fading consequences. In such instances, the customer cannot apprehend between an unexploited band and a profound fade. Hence, communal spectrum sensing is suggested to optimize sensing overall performance. We recognition performance of communal Spectrum Sensing with Selection Diversity Reception in Cognitive Radio. This study presents a simulation evaluation of choice diversity Reception based totally on fusion rule. Fusion rule is finished at the fusion centre (FC) to make the very last selection about the presence of PU. This leads that spectrum sensing is enthusiastically in the presence of Rayleigh. |
||||||

27
A Comparative Study on Classical Fourth Order and Butcher Sixth Order Runge-Kutta Methods with Initial and Boundary Value Problems
,
Mst. Sharmin Banu1*, Irfan Raju2, and Samiran Mondal1
1Department of Mathematics, Jashore University of Science and Technology, Jashore, Bangladesh; and 2Department of Arts and Sciences, Bangladesh Army University of Science and Technology, Saidpur, Bangladesh.
*Correspondence: msbsharmin_math@just.edu.bd (Mst. Sharmin Banu, Lecturer, Department of Mathematics, Jashore University of Science and Technology, Jashore, Bangladesh).
In this paper, it is discussed about Runge-Kutta fourth-order method and Butcher Sixth order Runge-Kutta method for approximating a numerical solution of higher-order initial value and boundary value ordinary differential equations. The proposed methods are most efficient and extolled practically for solving these problems arising indifferent sector of science and engineering. Also, the shooting method is applied to convert the boundary value problems to initial value problems. Illustrative examples are provided to verify the accuracy of the numerical outcome and compared the approximated result with the exact result. The approximated results are found in good agreement with the result of the exact solution and firstly converge to more accuracy in the solution when step size is very small. Finally, the error with different step sizes is analyzed and compared to these two methods. |
||||||

28
Enhance the LZW Compression Ratio Through the Use of Image Preprocessing Techniques for Gray Scale Images
,
Negesse Tadesse1*, Abebe Alemu1, and Abay Teshager1
1Dept. of Information Technology, Faculty of Informatics, University of Gondar, Gondar, Ethiopia.
*Correspondence: ngstds@hotmail.com (Negesse Tadesse, Dept. of Information Technology, Faculty of Informatics, University of Gondar, Gondar, Ethiopia).
Compression ratios of encoding algorithms degrade due to signal distortion, additive noise, and hacker manipulation. Large file size costs too much disk space, difficult to analyze, and high bandwidth to transmit over the internet. In this case, compression is mandatory. LZW is a general dictionary-based lossless compression algorithm. It is fast, simple, and efficient when it includes lots of repetitive data or monochrome images. Images with little data repetition and too much-blurred signal, the compression ratio of the LZW algorithm downgraded. Besides this, the execution time of the LZW compression algorithm increases dramatically. To preprocess and analyze the image information the researcher uses LZW encoding algorithm, bit plane slicing technique, Adaptive Median Filter, and MATLAB image processing toolbox. The MATLAB public grayscale image, salt & pepper, Gaussian locavore blurred, and Bayern pattern image data sets are used. Those images dataset is used to test the normal LZW encoding algorithm and the proposed encoding algorithm compression ratio step by step. The noised dataset, the filtered datasets, and bit plane dataset images are processed and recorded quality and compression ratio parameters. The enhanced encoding algorithm average compression ratio is better by far from the normal LZW encoding algorithm by 160%. Not only has the compression ratio, but demising also improved the algorithms execution time. And the image quality metrics measurement of mean square error, peak signal to noise ratio, and structural similarity index measurement are 0, 99, and 1 respectively. This implies the enhanced encoding algorithm could decompress fully without scarifying image quality. The LZW encoding algorithm developmental environment specifies to select tiff and gif image formats. In addition, the LZW encoding algorithm functions are not available in the MATLAB image processing toolbox. The researcher challenged to write a MATLAB script for each personal function. Still, there is room to extend the compression ratio of the LZW encoding algorithm using the image masking technique. |
||||||

29
Effect of Shift Parameters in Rational Krylov Subspace Method for Solving Riccati Equations Arise from Power System Models
,
Mahtab Uddin1&3*, M. Monir Uddin2, and Md. Abdul Hakim Khan3
1Institute of Natural Sciences, United International University, Dhaka-1212, Bangladesh; 2Department of Mathematics and Physics, North South University, Dhaka-1229, Bangladesh; and 3Department of Mathematics, Bangladesh University of Engineering and Technology, Dhaka-1000, Bangladesh.
*Correspondence: mahtab@ins.uiu.ac.bd (Mahtab Uddin, Assistant Professor, Institute of Natural Sciences, United International University, Dhaka-1212, Bangladesh).
The simulation of continuous-time algebraic Riccati equations (CARE) derived from the very large power system models is a highly laborious task and most cases infeasible due to the sophisticated structural ingredients. The computation is very time costly and the rate of convergence can be severely affected in the direct solvers. To overcome those adversities, an iterative approach Rational Krylov Subspace Method (RKSM) is introduced to deal with those large-scale CAREs. The solutions of those CAREs and hence the optimal feedback matrices can be efficiently explored by the RKSM approach to stabilize the power system models of unstable categories. In this approach, shift parameters play a vital role in the convergence of the computations and size of the solution spaces. The goal of the work is to investigate the effect of different types of shift parameters on the stabilization process. To attain the mentioned objective, a modified version of the iterative RKSM algorithm is proposed by employing two types of shift parameters, namely, the adaptive ADI shifts and heuristic shifts. Qualitative discussions for the outcomes for those shift parameters are narrated by tabular and figurative methods. |
||||||

30
The Physical Properties of ThCr2Si2- Type Co-based Compound SrCo2Si2: An ab-initio Study
,
Md. Shahidul Islam1, Md. Atikur Rahman2*, and Nahida Farjana2
1Department of Physics, Tarash Honours College, Tarash, Sirajganj, National University, Gazipur-1704, Bangladesh; 2Departments of Physics, Pabna University of Science and Technology, Pabna-6600, Bangladesh.
*Correspondence: atik0707phy@gmail.com (Md. Atikur Rahman, Assistant Professor, Departments of Physics, Pabna University of Science and Technology, Pabna-6600, Bangladesh).
In this article, we have studied the mechanical, electronic, and optical features of ThCr2Si2- type compound SrCo2Si2. The investigation has been done by using the first-principles method depend on the density functional theory (DFT) and the calculations were completed with the Cambridge Serial Total Energy Package (CASTEP) code. The optimized lattice parameters are well in accord with the existing synthesized values. The investigated elastic constants for this compound are positive which ensured the mechanical stability of this phase. The calculated values of Pugh’s ratio and Poisson’s ratio ensure the brittle character of SrCo2Si2. The universal anisotropic constant AU ensures the anisotropic behavior of SrCo2Si2.The softness nature of SrCo2Si2 is confirmed by the bulk modulus calculations. The overlapping of the valence band and conduction band near the Fermi level indicates the metallic nature of SrCo2Si2. At the Fermi level, the major contribution comes from Co-3d and Si-3p states. The large reflectivity in the high-energy region indicates that this compound might be useful as coating materials for reducing solar heating. The photoconductivity and absorption begin with zero photon energy which also ensures the metallic nature of SrCo2Si2. |