Authors:Nusrat Jahan Sima, Sagor Bisshas, Anik Rudra, Mohammad Shoeb, Abida Sultana Pages: 1 - 6 Abstract: The primary goal of this study was to determine the presence of potassium bromate in bread samples both qualitatively and quantitatively, as well as to investigate the composition of the bread (moisture, ash, and sugar contents). Thirty different commercial bread samples from different areas of Dhaka city were collected for analysis. The ultraviolet-visible spectrophotometric technique was employed in this study to estimate potassium bromate in bread samples. It was based on the redox interaction of bromate and promethazine hydrocloride in an acidic medium which generate a red-pink coloration with maximum absorbance at 515nm. The amount of potassium bromate was found in the range of 1.24 to 24.91µg/g. Moisture and ash content were found to be 15.37 to 29.8% and 1.75 to 2.94%, respectively. The total sugar content was determined by the ultraviolet-visible spectrophotometric method by the modified phenol-sulfuric acid test and the maximum absorbance was obtained at 489 nm. Total sugar content was found in different types of white bread samples ranging from 3.33 to 11.31g per 100g. The average recovery (n=5) of potassium bromate was 91.58 ± 5.61% at a dosage of 10 μg/mL. Dhaka Univ. J. Sci. 72(1): 1-6, 2024 (January) PubDate: 2024-03-25 DOI: 10.3329/dujs.v72i1.71027 Issue No:Vol. 72, No. 1 (2024)

Authors:Md Sagib, Bishnu Pada Ghosh, Nepal Chandra Roy Pages: 7 - 13 Abstract: Researchers are interested in the (1+1)-dimensional Camassa-Holm and Landau-Ginzburg-Higgs equations as they allow for the study of unidirectional wave propagation in shallow waters with a flat seabed, as well as nonlinear media exhibiting dispersion systems and superconductivity. This work has effectively developed exact wave solutions to the stated models, which may have significant consequences for characterising the nonlinear dynamical behaviour related to the phenomena. The extended -expansion technique is employed to procure a diverse array of progressive wave solutions characterized by hyperbolic, trigonometric, and rational functions. The solutions are shown as 3D profiles with a variety of shapes, including kink, singular kink, periodic, singular periodic, etc. The physical significance of the solutions is discussed by these plots, and the approach used in this study is considered efficient and capable of finding analytical solutions for the nonlinear models. Dhaka Univ. J. Sci. 72(1): 7-13, 2024 (January) PubDate: 2024-03-25 DOI: 10.3329/dujs.v72i1.71029 Issue No:Vol. 72, No. 1 (2024)

Authors:Haydory Akbar Ahmed, Rownak Jahan Tamanna, Md Israt Rayhan, Ishizaka Takami Pages: 14 - 23 Abstract: The covid-19 pandemic and the pre-pandemic internal-external economic shocks have inflicted the economies of Brazil, India, and Mexico. In this research, we hypothesize that both the shocks and pandemic perpetrated these economies. We employ the artificial neural network model to forecast GDP, consumption spending, and consumption to GDP ratio for these three economies over three cut-offs in 2016, 2019, and 2020. Our comparison of actual values with the forecasts over these three cut-offs shows that the pre-pandemic shocks have an impact albeit smaller than the pandemic. During the pandemic, we observed a V-shaped slump followed by recovery for both GDP, consumption spending, and consumption to GDP ratio. The Brazil and Indian economy’s recovery is perhaps weak. The Indian economy is going through a deeper slump in the post-pandemic era. We recommend cash transfer to low and low-middle income households to spur consumption spending and economic recovery. Dhaka Univ. J. Sci. 72(1): 14-23, 2024 (January) PubDate: 2024-03-25 DOI: 10.3329/dujs.v72i1.71176 Issue No:Vol. 72, No. 1 (2024)

Authors:Trishna Saha, Anamul Haque Sajib Pages: 24 - 29 Abstract: This paper aims to determine the significant factors which influence two correlated count responses, namely the total number of cars involved in an accident and the total number of fatalities due to that accident, of United Kingdom (UK) road accident count data. The bivariate Poisson (BVP) of two different forms and zero truncated bivariate Poisson regression (ZTBVP) models are considered to analyze UK road accident count data and the best model is selected based on the AIC and BIC values. From the data analysis, it is observed that the ZTBVP model provides the best fit (AIC value: 20563.26) for the UK road accident count data compared to all two variants of the BVP model (AIC value: >20563.26). From the results obtained from ZTBVP model, it is also observed that sex of driver, area, serious severity, and light condition are the significant covariates for the total number of cars involved in an accident while area, fatal severity, serious severity, light condition and year 2021 are the significant covariates for the total number of fatalities due to that accident. Dhaka Univ. J. Sci. 72(1): 24-29, 2024 (January) PubDate: 2024-03-25 DOI: 10.3329/dujs.v72i1.71181 Issue No:Vol. 72, No. 1 (2024)

Authors:Afsana Akter Mitu, M Babul Hasan Pages: 30 - 45 Abstract: The study of making the best decision under risk management in a variety of areas of our lives is known as Stochastic Programming. We will go through two-stage Stochastic Linear Programming approaches for a variety of real-world choice issues, as well as how to solve them. We will achieve this by constructing stochastic linear programming models based on real-world situations like the well-known Farmer's situation and News Vendors problems. The influence of pricing, Stochastic Integer Linear Programming problem, second stage Stochastic Integer Linear Programming problem, first stage Stochastic Binary Linear Programming problem, risk aversion problem, and continuous function for random variables based on two-stage SLP with the aid of Farmer's problem will all be examined. We will address the Newsvendor’s problem with Deterministic Equivalent Stochastic Linear Programming, an extension of Deterministic Stochastic Linear Programming for risk aversion with a high number of decision variables and restrictions, utilizing the two-stage Stochastic Linear Programming approach once more. Hand calculation is a challenging way to acquire the solution to the problems. As a result, we will use the programming language AMPL to design computer solutions for tackling both farmer and newsvendor difficulties. We will also utilize MATLAB to create graphs for the farmer's problem's continuous function. Dhaka Univ. J. Sci. 72(1): 30-45, 2024 (January) PubDate: 2024-03-25 DOI: 10.3329/dujs.v72i1.71183 Issue No:Vol. 72, No. 1 (2024)

Authors:Md Anwarul Islam Bhuiyan, Sohana Jahan, Mohammad Babul Hasan Pages: 46 - 55 Abstract: Data mining is the technique for deriving valuable data from a more extensive collection of raw data. It is the process of looking for irregularities, trends, and correlations in huge data sets in order to forecast results. Although a number of techniques have been developed to perform data mining on conventional data in the past years, there are huge scope to work with Interval Valued data (IVD). Working with IVD has been shown to be of significant importance when it comes to identifying the objective entity in a precise manner or representing incomplete knowledge on life situations. Unlike classical data where each object is represented by a point, in IVD the objects are represented by regions in Rp. In this paper, an extension of Principle Component Analysis (PCA) known as Vertices Principal Components method for interval-valued information has been explored. It additionally incorporated the relative contributions of the vertices depending on different choices of weighting schemes. A new idea for classification of the supervised IVD is proposed which is based on the idea of K-Nearest Neighbor (KNN) technique. The proposed approach is implemented on several benchmarking data sets. Numerical results suggest the proper choice of weighting schemes for each of the data set that will lead to better recognition rate. Dhaka Univ. J. Sci. 72(1): 46-55, 2024 (January) PubDate: 2024-03-25 DOI: 10.3329/dujs.v72i1.71184 Issue No:Vol. 72, No. 1 (2024)

Authors:Farzana Afroz Pages: 56 - 62 Abstract: The classical approach of estimating overdispersion parameter, Φ, by Pearson's goodness of fit statistic is not appropriate when the data are sparse. We have considered several estimators of Φ, derived from the Pearson's statistic and the deviance statistic for multinomial data. The proposed estimator of Φ depending on the deviance statistic is shown to perform the best for increasing level of sparsity and overdispersion, regarding the root mean squared error. As a practical example dead recovery data collected on Herring gulls from Kent Island, Canada are considered. A parametric extra variation model finite mixture distribution is used in the simulation study. Dhaka Univ. J. Sci. 72(1): 56-62, 2024 (January) PubDate: 2024-03-25 DOI: 10.3329/dujs.v72i1.71247 Issue No:Vol. 72, No. 1 (2024)

Authors:Md Mahmudur Rahman, Md Enamul Kabir, Md Mominul Islam, Md Abu Bin Hasan Susan, Muhammed Shah Miran Pages: 63 - 70 Abstract: In this work, pseudo-stem of a banana plant was used as a sustainable and affordable source to prepare porous carbon materials (PCM) on a large scale. After fine treatment, the material was annealed at 500, 600, and 700 °C using a tube furnace under nitrogen flow. The prepared materials were characterized by Fourier transform infrared (FT-IR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). FT-IR spectra show that the broad peak at the range of 1110-1160 cm-1 comes from the superimposed peaks of C-N for a single or more than one functional group which debunks the possibility of generating nitrogen-doped carbon. TEM and SEM analyses confirmed the porous structure of PCM with the pores connected to one, and a spongy structure was observed in the prepared carbon material. XRD analysis revealed that the carbon materials are crystalline. XPS investigation provided information regarding the dimension of which elements are present in the valence states and constituent elements, depicting the presence of a dominant graphitic C1speak at approximately 284 eV, along with a distinct O1s peak at around 532 eV. Additionally, a relatively weaker N1s peak (approximately 400 eV) was observed. Dhaka Univ. J. Sci. 72(1): 63-70, 2024 (January) PubDate: 2024-03-25 DOI: 10.3329/dujs.v72i1.71190 Issue No:Vol. 72, No. 1 (2024)

Authors:Maisha Binte Saif, Murshida Khanam Pages: 71 - 76 Abstract: Time series forecasting is a commonly applied method for scientific predictions. There are several econometric methods for forecasting time series observations and predicting the systematic pattern of underlying data. ARIMA model is most renowned in this aspect for its linearity. Nowadays a machine learning model namely artificial neural network (ANN) is gaining popularity for its nonlinear characteristics. Inconsistent conclusions may frequently be drawn when evaluating whether ARIMA models or neural networks are better at forecasting future events. For this reason, a hybrid methodology has been established in this study to get advantage from both linear and nonlinear modeling. The annual dataset of fish production in Bangladesh from 1990 to 2020 has been evaluated in this case. Formulating three measurement errors, RMSE, MAE and MAPE it has been demonstrated that the hybrid approach has high level of forecasting accuracy than the other two models in forecasting fish production data. Dhaka Univ. J. Sci. 72(1): 71-76, 2024 (January) PubDate: 2024-03-25 DOI: 10.3329/dujs.v72i1.71192 Issue No:Vol. 72, No. 1 (2024)

Authors:Hasina Akhter Simol, Istiak Hossain, Tapas Debnath, Pradip K Bakshi, Rumana Akther Jahan, Claus H Ruscher, Altaf Hussain Pages: 77 - 84 Abstract: Attempts have been made to synthesize vanadium doped rubidium hexagonal tungsten bronzes with the nominal composition RbxVyW1-yO3 (x = 0.30, 0.25, and 0.0 ≤ y ≤ x). The samples were synthesized using the solid state synthesis method in a silica glass tube under vacuum at (10-2 Torr) 700°C. The X-ray diffraction measurements reveal that a pure hexagonal tungsten bronze (HTB) phase can be formed with a 60% replacement of W5+ by V5+. The systematic incorporation of vanadium into the HTB lattice, as well as the reduction of V/W-O bond lengths in the xy plane and the lengthening of these bonds in the crystallographic c direction, are also revealed by Rietveld structure refinement of XRD data. The XRD results are supported by FTIR absorption spectra of the oxidized phases. Furthermore, an absorption signature develops as a function of y and exhibits a considerable increase in intensity with the eventual replacement of W5+ by V5+, showing a large decrease in the metallic like contribution and revealing the compounds' nonmetallic nature. Elemental analysis indicates good agreement with nominal values, demonstrating that vanadium was systematically incorporated into the RbxVyW1-yO3 system. Dhaka Univ. J. Sci. 72(1): 77-84, 2024 (January) PubDate: 2024-03-25 DOI: 10.3329/dujs.v72i1.71194 Issue No:Vol. 72, No. 1 (2024)

Authors:Md Lutfar Rahman Sarkar, M Z I Bangalee Pages: 85 - 91 Abstract: Because of the high-speed aircrafts, the distance to the other side of the world seems to be closer, as if it were situated just next door. Aerospace engineering has undergone a revolution thanks to research into airfoils. This research work has been focused on analyzing the aerodynamic performances of the NACA 4415 airfoil in turbulent flows while Mach numbers, and Reynolds numbers, have been taken into account. The chord length of and have been considered for this study. Computational fluid dynamics were employed to determine the lift, drag, and pitching moment forces, as well as their respective non-dimensional coefficients. As a result, maximum lift, moment forces have been found after the angle of attacks, and stagnation areas are increasing dramatically behind the airfoil, proportion to the increments with the angle of attack. Additionally, the effects of pressure and velocity on every point of the airfoil's surface were studied through the analysis of pressure and velocity contours. Dhaka Univ. J. Sci. 72(1): 85-91, 2024 (January) PubDate: 2024-03-25 DOI: 10.3329/dujs.v72i1.71196 Issue No:Vol. 72, No. 1 (2024)

Authors:Mohammad Mohsin, Umme Muslima, Sadia Afrin Chhanda, Tanvir Muslim Pages: 92 - 97 Abstract: The qualitative phytochemical screening of leaves and stems of Coffea benghalensis B. Heyne Ex Schult showed the presence of saponins, flavonoids, steroids, and cardiac glycoside. Stigmasterol, 1, 3- stearyl-oleyl-glyceride and stigmasterol glucoside were isolated and characterized from the dichloromethane extract of this plant leaves and stems by chromatographic and spectroscopic methods. Total caffeine content per hundred grams was estimated. Fatty acids were analyzed quantitatively by GLC. Total antioxidant capacity and antimicrobial activity of the plant leaves and stems extract were studied. Dhaka Univ. J. Sci. 72(1): 92-97, 2024 (January) PubDate: 2024-03-25 DOI: 10.3329/dujs.v72i1.71197 Issue No:Vol. 72, No. 1 (2024)