Search

Filtration is a very basic and primitive technique of water treatment. For many remote, under-privileged and poor communities, this is the only pre-treatment of drinking water prior to boiling. With the emergence of arsenic contaminations in many groundwater aquifers, the filtration became imperative for many communities around the world. However, after repetitive/continuous uses, clogging of the filter media is obvious, which eventually causes poor performance of the filtration process. Backwashing is a common technique being used for the recovery of the filtration capacity of clogged filter media. This study presents development of a simple clogging and backwashing efficiency model for a special filter media. “3rd generation IHE family filter” was developed by UNESCO-IHE Institute for Water Education and widely used for treating arsenic-contaminated water in many countries including Bangladesh. Several field tests were conducted in three different sites in Bangladesh having different qualities of influent water. Developed model coefficients were derived using the collected data on flow measurements through the device during successive clogging and backwashing periods up to four months. Developed model with the selected model coefficients can simulate field measurements on flow retardation and recovery with good accuracy. Eventually, selected model coefficients for three sites were correlated with the respective influent water quality. It was found that the coefficients are linearly correlated with the iron and ammonium contents of inflow water. [ABSTRACT FROM AUTHOR]

• A method for recording crack rubbing/clapping AE signals is proposed. • An experimental setup for recording fatigue crack rubbing/clapping AE was designed. • A test fixture was manufactured to load the specimen and perform vibration. • AE during rubbing/clapping of an unconstrained and loaded specimen were recorded. • Proposed correlation analysis can compare a large number of AE signals. Fatigue cracking in sheet metal structures is a common problem during practical applications. It can cause a disastrous failure in the running condition of the structure if it is not addressed in time. A crack can potentially produce acoustic emission (AE) signals during the crack growth event as well as during rubbing/clapping of faying surfaces. All kind of AE signals from the crack provide useful information regarding the condition of the cracked structure. AE signals due to crack faying surface rubbing/clapping need to be identified and separated from AE signals due to other sources. This paper discusses the study of the AE signals generated due to rubbing/clapping of crack faying surfaces. The initial fatigue crack was generated in a sheet metal sample through fatigue loading. The sample was then vibrated at various frequencies using a vibration exciter, and AE signals were generated by vibration induced rubbing/clapping of crack faying surfaces. AE signal signature due to vibration induced rubbing/clapping was identified and studied. AE signal due to rubbing/clapping of sheet metal sample while undergoing an axial static load is also discussed in this paper. The sheet metal sample with fatigue crack was axially loaded using a test cell manufactured in-house for loading sheet metal samples. The samples were vibrated to excite AE signals, and the influence of static load on crack rubbing/clapping AE signals were studied. The vibration-induced crack faying surface motion generated a large number of AE signals. A comparison among these AE signals was performed by using the Pearson correlation of the signals. The first novelty of this research is experimental design and fabrication of an experimental setup for detecting vibration induced rubbing and clapping in fatigue cracked metallic structures. The second novelty of this research is the development of a novel correlation coefficient based approach for comparing a large number of AE signals. [ABSTRACT FROM AUTHOR]

• >60% of survey population in South Asia is willing to be vaccinated against COVID-19 • Age, sex, education and comorbidities are associated with vaccine acceptance • A large number of people are worried about the effectiveness of COVID-19 vaccine • Women were more willing than men to be vaccinated With COVID-19 vaccination underway, this study aimed to understand belief, attitude and intention of the people in the South Asia region towards the vaccine. We conducted a cross-sectional study using semi-structured questionnaires among 18201 individuals in four South Asian countries; Bangladesh, India, Pakistan, and Nepal between January 17 and February 2, 2021. We used the Health Belief Model (HBM) to identify the predictors related to vaccine acceptance. STATA (v16.1) was used for all analyses. The percentage of respondents willing to be vaccinated against COVID-19 was 65%, 66%, 72% and 74% for Bangladesh, India, Pakistan and Nepal, respectively. Perceived destructive impact of COVID-19, positive perception of vaccines and concern about possible side effects were significant in modifying respondents' intentions.. In multivariable logistic regression, age, sex, marital status, education, comorbidities, worry about getting infected, perceived COVID-19 impact, belief regarding vaccine efficacy, positive attitude towards mandatory measures, and vaccine availability were found to be associated with vaccine acceptance across countries. Nearabout two-third of the respondants were willing to take COVID-19 vaccine in the four South Asia countries. [ABSTRACT FROM AUTHOR]