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This paper presents condition monitoring, fault detection, and control of vibration of a rotating system using vibration analysis. The system includes ball bearings, pulleys, impellers, shafts, and an electric motor. The experimental approach generated different levels and forms of vibration that were measured using a vibration analyzer (CSI 2140). A vibration analyzer is used for determining the characteristics and nature of vibration of the experimental system. System vibrations were measured in terms of amplitude, phase angle, and frequency during the experimental operating conditions. After that, the experimental results were compared with the ideal working conditions mentioned in the ISO standard for the determination of machine health and condition monitoring. This paper also presents a passive control technique to enhance the machine’s health condition. The generated faults of the system have been detected and solved by using an exact measurement of polar plot analysis. This approach of condition monitoring, fault detection, and improving operating conditions can be used to visualize and analyze vibration data in any rotating system. Furthermore, this technique would be a feasible and effective way of finding strategies for the maintenance of rotary machines.

An integrated approach was used to estimate the number of COVID-19 patients related to air quality and meteorological phenomena. Additionally, the air quality during pre-lockdown, lockdown, and post-lockdown stages of the COVID-19 pandemic was assessed to determine the effect of the infection containment measures taken in Bangladesh during the pandemic. The air quality was assessed based on measurements of nitrogen dioxide (NO2), sulfur dioxide (SO2), ozone (O3), carbon monoxide (CO), black carbon, particulate matter (PM2.5 and PM10), and aerosol optical depth. Time-averaged maps of these parameters have been generated from NASA’s (National Aeronautics and Space Administration) website. Values of these parameters have also been collected from a continuous air monitoring station (CAMS) located in Bangladesh’s north-western city Rajshahi. The comparison shows that lockdown during the pandemic has brought significant improvements in air quality. However, the improvement was not sustained, since rapid increases in the air pollutant concentrations were observed in the post-lockdown period. Furthermore, Pearson correlation coefficients between each air quality variable and the daily new COVID-19 case rates were calculated. Different meteorological variables during the same time periods were determined to observe the variation in Rajshahi city. Relationships of these variables with the case rates were also established. Additionally, statistical analyses of the obtained data have been conducted for the measured variables using the Kruskal–Wallis test to assess the differences in the observed data among the pre-lockdown, lockdown, and post-lockdown periods. Dunn’s “Q” test was employed to test if the variables showed significance statistical difference during the Kruskal–Wallis test for pairwise comparisons. From the study, it has been observed that both meteorological variables and air quality parameters have significant relationship with daily new COVID-19 case rates. Both positive and negative associations of these parameters with the COVID-19 case rates have been observed. Very high air pollution has been observed in the post-lockdown period. Thus, it is recommended that appropriate authorities undertake corrective measures to protect the environment in cities with large populations. This study provides guidance for decision makers and health officials for future research and potentially reducing the spread of COVID-19.

Waste management is becoming one of the most challenging tasks for developing countries in order to ensure good human health, as well as a healthy environment. Rajshahi City Corporation (RCC) is one of the 12 city corporations in Bangladesh. Various environmental and human health problems have arisen due to a lack of proper knowledge of waste management. Thus, the aim of this work is to illustrate the present status of MSW generation and management in Rajshahi City Corporation, Bangladesh. Fifty households were selected throughout RCC for waste collection, which represent approximately all types of households in RCC. From the qualitative and quantitative analysis, it is estimated that the approximate MSW generation in RCC is 358.19 t/d (tons/day) at an approximate rate of 0.4214 kg/person/d. Calorific values of the wastes have also been determined using the ultimate analysis results of the MSW. A higher calorific value of the dry MSW has been calculated as 14.9 MJ/kg. Moisture content of the MSW has been found to be 48.28%. It is also estimated that the possible power generation (steam energy to electrical power) from MSW generated in RCC is 159.40 MWh/d. Lastly, future scopes of MSW management and different waste management measures that need to be taken are illustrated. Waste-to-energy (WTE) conversion has been given priority and anaerobic digestion (AD) has been found to be an interesting prospect in this sector. Techno-economic analysis of the AD has been conducted. Energy potential from the proposed plant has been calculated as 3.85 MW and the payback period has been found to be 4.9 years. It has been observed that employing AD on a large scale can not only reduce the waste, but also meet a large portion of the energy demand of this city.