Simulation of Severe Thunderstorms in Conjugation of Westerly and Easterly on 31 March 2019 in Bangladesh

The diagnostic and prognostic studies of thunderstorms/squalls are very important to save live and loss of properties. The present study aims at diagnose the different tropospheric parameters, instability and synoptic conditions associated the severe thunderstorms with squalls, which occurred at different places in Bangladesh on 31 March 2019. For prognostic purposes, the severe thunderstorms occurred on 31 March 2019 have been numerically simulated. In this regard, the Weather Research and Forecasting (WRF) model is used to predict different atmospheric conditions associated with the severe storms. The study domain is selected for 9 km horizontal resolution, which almost covers the south Asian region. Numerical experiments have been conducted with the combination of WRF single-moment 6 class (WSM6) microphysics scheme with Yonsei University (YSU) PBL scheme in simulation of the squall events. Model simulated results are compared with the available observations. The observed values of CAPE at Kolkata both at 0000 and 1200 UTC were 2680.4 and 3039.9 J kg-1 respectively on 31 March 2019 and are found to be comparable with the simulated values. The area averaged actual rainfall for 24 hrs is found is 22.4 mm, which complies with the simulated rainfall of 20-25 mm for 24 hrs. Journal of Engineering Science 12(3), 2021, 29-43

Assessment of Urban Resiliency Concerning Disaster Risk: A Review on Multi- Dimensional Approaches

There have been a number of new research published with different methodologies and frameworks in recent years, aimed at improving city resilience to a variety of man-made and natural calamities. As climate change progresses, resilience will become a more important topic in scientific and policy circles that influence future urban development. This review article first provides the definition of resilience. Then it represents some of the adopted methodologies in an extensive way. Approaches including Baseline Resilience Indicators for Communities (BRIC), Climate Disaster Resilience Index (CDRI), Disaster resilience index based on Analytic Hierarchy Process (AHP), Composite indicator based approach, Hyogo Framework and so on. This section discusses about urban resiliency assessments to mitigate vulnerability, offer a set of principles and indicators for creating an urban resilience assessment tool. Findings of this study not only address a variety of qualitative and quantitative aspects of urban resilience but also describes about different indicators such as environmental resources, socio-economic and built environment, infrastructure, governance and institutional indicators. Journal of Engineering Science 12(3), 2021, 111-125

Impact of Human Intervention and Sea Level Rise on Water-Logging Scenarios inside Polders-24 And 25 of Bangladesh

Coastal region of Bangladesh possesses a fragile ecosystem and is exposed to hazards like cyclones, floods, storm surges, and water-logging. A detail understanding on the impact of water-logging due to various natural, man-made and climate change scenarios is still lacking. Considering this research gap, the present research is aimed to study impacts of these scenarios inside polders-24 and 25 which are situated on the western part of the coastal region. In this Study as natural scenario, sedimentation in the Hari River; as man-made scenario, new polders in the south-central region and as SLR scenario, an extreme sea level rise of 1.48m are considered. Long-term satellite images are analyzed, and numerical model is applied in the study area. The result shows that water-logging is more acute inside polder-25 compared to polder-24. Sedimentation in Hari River aggravates the water-logging condition. Dredging in Hari River does improve the situation. Journal of Engineering Science 12(3), 2021, 73-83

The Efficacy of the WRF-ARW Model in the Genesis and Intensity Forecast of Tropical Cyclone Fani over the Bay of Bengal

An attempt has been carried out to assess the efficacy of the Weather Research and Forecasting (WRF) model in predicting the genesis and intensification events of Very Severe Cyclonic Storm (VSCS) Fani (26 April – 04 May 2019) over the Bay of Bengal (BoB). WRF model has been conducted on a single domain of 10 km horizontal resolution using the Global Data Assimilation System (GDAS) FNL (final) data (0.250 × 0.250). According to the model simulated outcome analysis, the model is capable of predicting the Minimum Sea Level Pressure (MSLP) and Maximum Sustainable Wind Speed (MSWS) pattern reasonably well, despite some deviations. The model has forecasted the Lowest Central Pressure (LCP) of 919 hPa and the MSWS of 70 ms-1 based on 0000 UTC of 26 April. Except for the model run based on 0000 UTC of 26 April, the simulated values of LCP are relatively higher than the observations. According to the statistical analysis, MSLP and MSWS at 850 hPa level demonstrate a significantly greater influence on Tropical Cyclone (TC) formation and intensification process than any other parameters. The model can predict the intensity features well enough, despite some uncertainty regarding the proper lead time of the model run. Reduced lead time model run, particularly 24 to 48 hr, can be chosen to forecast the genesis and intensification events of TC with minimum uncertainty. Journal of Engineering Science 12(3), 2021, 85-100

Structural and Dielectric Progression of 5 % Gd Doped BiFeO3 Nanoparticles Through Cr (2-8%) Doping

This study reports the structural modifications in undoped multiferroic BiFeO3 (bismuth ferrite or BFO) nanoparticles caused by doping at both the A-site (by 5% Gd) and B-site (by 2-8% Cr) and the resulting improvements in dielectric characteristics. Both un-doped and doped BFO nanoparticles were synthesized using the sol-gel technique and annealed at 600°C for crystallization. X-ray diffractometry (XRD) reveals a phase transition from rhombic (R3c) to orthorhombic (Pn21a). Field Emission Scanning Electron Microscopy (FESEM) study shows the production of nanoparticles with sizes ranging from 80 to 130 nm. Impedance analyzer experiments (100 Hz-10 MHz) show that the dielectric characteristics of doubly doped BFO are very stable over a wide frequency range. The dielectric permittivity of co-doped BFO decreases with Cr doping concentration up to x = 0.06 before reversing. The conductivity drops dramatically as the Cr content rises. Journal of Engineering Science 12(3), 2021, 101-110

Influence of Aluminium and Autoclaving Temperature on the Properties of Autoclaved Aerated Concrete

Autoclaved aerated concrete (AAC) prepared by the mixing of ordinary Portland cement, lime powder, sand, aluminium powder and water. This study covers the variation of physical, mechanical and functional properties of autoclaved aerated concrete with autoclaving temperature and aluminium content and compared with that of normal weight cement mortar sample. In this work, two dosage of aluminium content of 0.4% and 0.8% of the dry weight of ordinary Portland cement and three different autoclaving temperature of 160oC, 180oC and 200oC were used. AAC sample with 0.8% aluminium and 160oC temperature had unit weight of 1490kg/m3 which was lowest among all samples including the control or normal weight cement blocks. Weight reduction of AAC sample was 31.53%. AAC sample with 0.4% aluminium and 200oC autoclaving temperature gave maximum compressive and tensile strength of 19.4MPa and 1.81MPa respectively which were close to that of normal weight concrete and strength of AAC increased with autoclaving temperature and decreased with aluminium content. In this research, the functional propertiesof AAC, absorption capacity was much higher than normal weight concrete and this capacity was increased with aluminium content and with decreasing autoclaving temperature and unit weight of AAC. For AAC with 0.8% aluminium and 160oC temperature gave maximum water absorption capacity (=9.93%). Again, surface absorption rate was higher for first 12hours and with time it would be constant because of its saturated position. Journal of Engineering Science 12(3), 2021, 11-17

Environmental Monitoring at and around the Matuail Landfill Site of Dhaka City using Remote Sensing

Rapid urban population growth and flourishing incomes have increased waste production in Dhaka city. A part of daily produced Municipal Solid Waste (MSW) is disposed of at Matuail sanitary landfill located within Jatrabari Thana, Dhaka. This study has analyzed the environmental impacts at and around this landfill using remote sensing techniques. The objective of this research is to develop a means of environmental monitoring at the landfill site and its surroundings through the implementation of various time-series remote sensing indices e.g., Land Surface Temperature (LST), Normalized Difference Vegetation Index (NDVI), Soil Adjusted Vegetation Index (SAVI), and Modified Soil Adjusted Vegetation Index (MSAVI). LST is used to observe the Spatio-temporal pattern of temperature distribution. NDVI, SAVI, and MSAVI are the Bio-indicators and they are helpful to analyze the vegetation health condition at and around the landfill area. From the result of LST, it is observed that the average temperature of the Jatrabarithana has increased from 23.12℃ in 1993 to an optimum temperature of 35.20℃ in 2013, then it went down to 29.09℃ in 2018. The NDVI result for the study period shows that the percentages of ‘Bare Soil’ and ‘Structural Object’ have increased drastically from 10% to 41.20% and 13.30% to 31.52% respectively for these 25 years in Jatrabarithana. On the other hand, the percentages of ‘Shrub and Grassland’ and ‘Moderate Vegetation’ have decreased from 54.20% to 25.15% and 12.55% to 0% respectively. SAVI and MSAVI also show evidence of increasing the amount of bare soil and structural object and decreasing the amount of vegetation. Due to the waste stabilization process, and inappropriate management system at the Matuail landfill, along with urbanization, industrial activity, and deforestation, a harmful effect has been done to the surrounding environment. As an outcome, the temperature has risen rapidly and the amount of vegetation has declined to a significant extent. Journal of Engineering Science 12(3), 2021, 127-138

Water Quality Index (WQI) of Shitalakshya River Near Haripur Power Station, Narayanganj, Bangladesh

The present investigation is aimed at understanding the water quality parameters and the findings of a water quality index (WQI) to assess the characteristics of the Shitalakshya River near Haripur power station, Narayanganj for five different years (2013-2018) considering monsoon, pre-monsoon, post-monsoon seasonal variations. In this study, three different methods were used to evaluate the WQI named as; Weighted Arithmetic Index Method, Canadian Council of Ministers of the Environment (CCME) WQI Method and National Sanitation Foundation (NSF) Method. Essential parameters i.e. dissolved oxygen, pH, chloride, turbidity, color, biochemical oxygen demand, total dissolved solids, Silica, Iron, electrical conductivity, Phosphate were considered for calculating the WQI. According to Weighted Arithmetic Index Method, the WQI value varied from 80 to 286 for the last five years. From the National Sanitation Foundation Method, the WQI value was found within 36 to 56 for the study duration. The WQI value was varied from 3 to 16 according to the Canadian Council of Ministers of the Environment Water Quality Index Method. Based on WQI values, the Shitalakhya river water was being classified as poor water for the above-mentioned different years. Among the different parameters, mostly turbidity, electrical conductivity, TSS, Iron were the parameters that caused the situation worst. Journal of Engineering Science 12(3), 2021, 45-55

Effect of Oxidizers on Sulphide Removal from Hair Dissolving Liming Wastewater in Tannery

Liming and unhairing is the conventional operation in the tannery where raw animal skins are treated with sodium sulphide and calcium hydroxide to remove keratin proteins e.g., hair and wool epidermis and to dissolve nonstructural proteins. The hair dissolving liming process discharges wastewater containing soluble sulphide. In acidification, the sulphide in wastewater generates toxic hydrogen sulphide, which has a negative impact on the environment. In this present study, the efficiency of hydrogen peroxide (H2O2) and sodium chlorite (NaClO2) oxidizers are compared to remove sulphide from the hair dissolving liming wastewater. The soluble sulphide in the raw liming wastewater was 3666 mg/L. At optimized dose and pH for H2O2 and NaClO2 soluble sulphide in the solution were 109.2 and 54.6 mg/L, respectively. The sulphide removal efficiency for H2O2and NaClO2 were 97.0% and 98.5%, respectively at an optimum pH (pH 7). Before and after treatment the physicochemical parameters of the liming wastewater were analysed by observing different water quality parameters viz: pH, TDS, EC and salinity. At optimized condition TDS and salinity removal efficiency was 47.2%, 52.3% and 8.1%, 11.2% for H2O2 and NaClO2, respectively. This simple and easy method would be effective for treating hair dissolving liming wastewater in reducing soluble sulphide discharge from the tanneries. Journal of Engineering Science 12(3), 2021, 67-72

Impact of Physical Factors of Workplace Environment on Workers Performance in Industry

Workers’ performance and efficiency are dependent on their workplace facilities. The present study attempts to identify the six physical factors of the workplace environment: furniture and equipment design, air quality, temperature, sanitation, lighting and noise. Workers' feedback is evaluated by using 5 scale Likert method and it is found that found workplace temperature is most critical for workers' performance. The purpose of this study is to identify workers' impressions about their workplace environment and provide a better understanding to the managers about improvement. Industry-level emphasis on these factors can improve workers' performance standards and production quality. Previous work performance studies are not focused on hygiene and sanitation facility but due to the corona pandemic situation sanitation concern has been raised. This study aims to explore the relationship of these factors with gender and work experience of the workers. Variation in each group has provided an understanding of the basic demand of each type of worker. Journal of Engineering Science 12(3), 2021, 57-66