Investigation of Jet Formation Following Droplet Impact on Microholed Hydrophilic Substrate

Droplet impingement on solid hydrophobic and superhydrophobic surfaces produces diverse phenomena, including spreading, splashing, jetting, receding, and rebounding. In microholed surfaces, downward jets through the hole can be caused by high impact inertia and the cavity collapse formed during the droplet's recoiling. With enough impact inertia, the jets can pinch off the substrate and eventually form a smaller droplet or break up into several satellite droplets. In this work, the dynamics of downward jets through the micro-holes that form during the impact of water droplets impinging upon hydrophilic substrates were investigated experimentally. The small circular holes of ~600 µm diameter were created in the 200-µm thick plastic film substrates using a 0.5 mm diameter punch. A 10µL-pipette tip with a syringe pump was used to produce the millimeter-sized droplets. Great care has been taken to ensure that the microscopic droplets can directly impact over the micro-holes. The entire process of water droplets impacting micro-holed substrate was studied in detail using two high-speed video photography cameras. A MATLAB code has been developed to quickly process a large number of captured images from experiments to characterize the droplet impact and jet dynamics, such as the spreading factor, jet formation, jet length, breakup time, and satellite droplet volume. We found the jetting mechanism and volume penetrating through the microhole are directly influenced by the impact velocity of the droplet. When the impact velocity is lower than a threshold value, the jet driven by the impact inertia will not be able to pinch off from the substrate. Above the threshold velocity, the jet pinches off to form single or multiple droplets. The pinch-off time was closely related to the capillary-inertial time scale. For relatively high impact velocity, the jet stretched longer and broke up into multiple droplets due to Plateau–Rayleigh instability.We found the maximum length of the jet before its breakup is related to the impact velocity and Weber Number. A regime map has been produced to introduce the relation between Weber numbers and jet breakup conditions. The volume of the 1st satellite droplet was independent of the Weber number with an average normalized value of 0.018. We also found that the total volume of the ejected jet depends on the Weber Number differently for different ranges of We. Moreover, the maximum spreading factor (βm), maximum jet length (Lm), and necking radius were found to follow scaling laws as βm ~We0.22, Lm ~ 7.44 Ui, and rn/lc ~ τα, respectively. Also, the maximum and average speeds of the jet were found to vary linearly with the impact speed of the droplet. Significantly, this study has reported an upward jetting for a specific range of Weber Numbers. The upward jet speed, width, and time required to form the jet follow the particular trend with Weber Number. However, the top droplet speed and diameter require further investigation to determine the trend they follow

Bank Selection Influencing Factors: A Study on Customer Preferences with Reference to Rajshahi City

This study analyses the factors considered important by customer in selection a private commercial bank and nationalized commercial bank in Bangladesh. It is based on a survey of 600 customers of private commercial banks (PCBs) and nationalized commercial banks (NCBs) located in the city of Rajshahi in Bangladesh. This study relied on 30 selection factors extracted from relevant literature, personal experience, and interviews with the some bank officials and customers. The findings reveal that the most important factors influencing customers for selecting a private commercial bank are effective and efficient customer services, speed and quality services; image of the bank, online banking, and well management. On the other hand, the most important factors for choosing a nationalized commercial bank are low interest rate on loan, convenient branch location, safe investment (accountability of the govt.), variety of services offered and low eservice charges. Findings also suggest that there are some of significant statistical differences between responses of PCB and NCB customers related to factors considered important in selection a bank

Enzyme-Accelerated Acid Hydrolysis of Untanned Proteinaceous Wastes from Tanning Industry

Traditionally, tanning industry has been producing considerable amounts of solid wastes, which raises serious concerns on account of their environmental impact. Out of these, untanned raw trimmings account for about 5-7% of the total quantity of raw materials processed. This waste could be a value-added cheap source of collagen, which has numerous industrial applications if properly and scientifically utilized. This research work deals with the utilization of raw trimmings of solid waste from tanneries in the process of enzymatic hydrolysis, performed by using acetic acid and protease, in order to obtain protein hydrolysate. The hydrolysis was carried out with varying acid concentrations, acid solutions, temperatures and times. The maximum obtained protein hydrolysate was about 88% at 1.5 M acid concentration, 4% enzyme ratio, and 60 °

Lack of Knowledge Is the Leading Key for the Growing Cervical Cancer Incidents in Bangladesh: A Population Based, Cross-Sectional Study

Introduction Cervical cancer is the second most common gynecological cancer in Bangladesh. Lack of awareness of screening methods, risk factors, and symptoms may lead to presenting most cervical cancers at an advanced stage. We investigated knowledge and awareness of cervical cancer (CCa) among females at the Sheikh Hasina Medical College (SHMC) of Tangail district in Bangladesh. Methods A cross sectional survey was conducted to collect data via a structured questionnaire from SHMC during the period of February 2019 to January 2020. Data on socio-demographic characteristics and knowledge of cervical cancer were collected. Multivariable logistic regression models were used to identify factors associated with having heard and knowledge of cervical cancer. A p-value \u3c 0.05 was considered significant. Result Of all the interviews conducted, only 45.2% (493/1090) had heard of cervical cancer as a disease. Women were more likely to be aware of CCa if they were lived in urban areas, had higher education (university level education) and belong to high income families. The study revealed evidence of significant association between marital, literacy, residence and socio-economic status with women’s knowledge on cervical cancer (p\u3c 0.05). Conclusion This study serves to highlight that there was impoverished knowledge about cervical cancer among Bangladeshi women. Hence, this indicates the government should take proper steps to raise awareness and knowledge levels via educational programs and health counseling

Band gap tuning of perovskite solar cells for enhancing the efficiency and stability: Issues and prospects

The intriguing optoelectronic properties, diverse applications, and facile fabrication techniques of perovskite materials have garnered substantial research interest worldwide. Their outstanding performance in solar cell applications and excellent efficiency at the lab scale have already been proven. However, owing to their low stability, the widespread manufacturing of perovskite solar cells (PSCs) for commercialization is still far off. Several instability factors of PSCs, including the intrinsic and extrinsic instability of perovskite materials, have already been identified, and a variety of approaches have been adopted to improve the material quality, stability, and efficiency of PSCs. In this review, we have comprehensively presented the significance of band gap tuning in achieving both high-performance and high-stability PSCs in the presence of various degradation factors. By investigating the mechanisms of band gap engineering, we have highlighted its pivotal role in optimizing PSCs for improved efficiency and resilience

Perovskite materials in X-ray detection and imaging: Recent progress, challenges, and future prospects

Perovskite materials have attracted significant attention as innovative and efficient X-ray detectors owing to their unique properties compared to traditional X-ray detectors. Herein, chronologically, we present an in-depth analysis of X-ray detection technologies employing organic-inorganic hybrids (OIHs), all-inorganic and lead-free perovskite material-based single crystals (SCs), thin/thick films and wafers. Particularly, this review systematically scrutinizes the advancement of the diverse synthesis methods, structural modifications, and device architectures exploited to enhance the radiation sensing performance. In addition, a critical analysis of the crucial factors affecting the performance of the devices is also provided. Our findings revealed that the improvement from single crystallization techniques dominated the film and wafer growth techniques. The probable reason for this is that SC-based devices display a lower trap density, higher resistivity, large carrier mobility and lifetime compared to film- and wafer-based devices. Ultimately, devices with SCs showed outstanding sensitivity and the lowest detectable dose rate (LDDR). These results are superior to some traditional X-ray detectors such as amorphous selenium and CZT. In addition, the limited performance of film-based devices is attributed to the defect formation in the bulk film, surfaces, and grain boundaries. However, wafer-based devices showed the worst performance because of the formation of voids, which impede the movement of charge carriers. We also observed that by performing structural modification, various research groups achieved high-performance devices together with stability. Finally, by fusing the findings from diverse research works, we provide a valuable resource for researchers in the field of X-ray detection, imaging and materials science. Ultimately, this review will serve as a roadmap for directing the difficulties associated with perovskite materials in X-ray detection and imaging, proposing insights into the recent status, challenges, and promising directions for future research

Service Quality of Five Star Hotels in Bangladesh: An Empirical Assessment

Although the importance of service quality and service quality measurement have been recognized, there are limited researches that have addressed the structure and antecedents of the concept for the hotel industry in Bangladesh. The clarification of the dimensions of service quality is inevitable for the managers in the hotel industry as these identify the bundles of service attributes consumers find important. Therefore, this study aims to measure the service quality from the customers’ perspective of five star hotels in Bangladesh based on the SERVQUAL model. Three five star hotels (Ruposhi Bangla Hotel, Pan Pacific Sonargaon Hotel, and Radison Water Garden Hotel) out of four were selected for the purpose of the study. The study is based on the primary data collected from the respondents with the help of a self-administered questionnaire to measure the perception of service quality characteristics of the five star hotels. Data analysis has been done using SPSS software and a factor analysis has been conducted to measure the differences among the factors affecting service quality perceptions. To measure the service quality gap, five dimensions related to hotel industry were identified. The analysis shows that the service quality of the five star hotels is highly dependent on the physical appearance, interior decoration, food quality, behavior of the employees, security system, and customized services given to individual customers. &nbsp

Service Quality of Five Star Hotels in Bangladesh: An Empirical Assessment

Although the importance of service quality and service quality measurement have been recognized, there are limited researches that have addressed the structure and antecedents of the concept for the hotel industry in Bangladesh. The clarification of the dimensions of service quality is inevitable for the managers in the hotel industry as these identify the bundles of service attributes consumers find important. Therefore, this study aims to measure the service quality from the customers’ perspective of five star hotels in Bangladesh based on the SERVQUAL model. Three five star hotels (Ruposhi Bangla Hotel, Pan Pacific Sonargaon Hotel, and Radison Water Garden Hotel) out of four were selected for the purpose of the study. The study is based on the primary data collected from the respondents with the help of a self-administered questionnaire to measure the perception of service quality characteristics of the five star hotels. Data analysis has been done using SPSS software and a factor analysis has been conducted to measure the differences among the factors affecting service quality perceptions. To measure the service quality gap, five dimensions related to hotel industry were identified. The analysis shows that the service quality of the five star hotels is highly dependent on the physical appearance, interior decoration, food quality, behavior of the employees, security system, and customized services given to individual customers

Tree species that 'live slow, die older' enhance tropical peat swamp restoration : Evidence from a systematic review

Degraded tropical peatlands lack tree cover and are often subject to seasonal flooding and repeated burning. These harsh environments for tree seedlings to survive and grow are therefore challenging to revegetate. Knowledge on species performance from previous plantings represents an important evidence base to help guide future tropical peat swamp forest (TPSF) restoration efforts. We conducted a systematic review of the survival and growth of tree species planted in degraded peatlands across Southeast Asia to examine (1) species differences, (2) the impact of seedling and site treatments on survival and growth and (3) the potential use of plant functional traits to predict seedling survival and growth rates. Planted seedling monitoring data were compiled through a systematic review of journal articles, conference proceedings, reports, theses and unpublished datasets. In total, 94 study-sites were included, spanning three decades from 1988 to 2019, and including 141 indigenous peatland tree and palm species. Accounting for variable planting numbers and monitoring durations, we analysed three measures of survival and growth: (1) final survival weighted by the number of seedlings planted, (2) half-life, that is, duration until 50% mortality and (3) relative growth rates (RGR) corrected for initial planting height of seedlings. Average final survival was 62% and half-life was 33 months across all species, sites and treatments. Species differed significantly in survival and half-life. Seedling and site treatments had small effects with the strongest being higher survival of mycorrhizal fungi inoculated seedlings; lower survival, half-life and RGR when shading seedlings; and lower RGR and higher survival when fertilising seedlings. Leaf nutrient and wood density traits predicted TPSF species survival, but not half-life and RGR. RGR and half-life were negatively correlated, meaning that slower growing species survived for longer. Synthesis and applications. To advance tropical peat swamp reforestation requires expanding the number and replication of species planted and testing treatments by adopting control vs. treatment experimental designs. Species selection should involve slower growing species (e.g. Lophopetalum rigidum, Alstonia spatulata, Madhuca motleyana) that survive for longer and explore screening species based on functional traits associated with nutrient acquisition, flooding tolerance and recovery from fire.Peer reviewe

Tree species that 'live slow, die older' enhance tropical peat swamp restoration : Evidence from a systematic review

Degraded tropical peatlands lack tree cover and are often subject to seasonal flooding and repeated burning. These harsh environments for tree seedlings to survive and grow are therefore challenging to revegetate. Knowledge on species performance from previous plantings represents an important evidence base to help guide future tropical peat swamp forest (TPSF) restoration efforts. We conducted a systematic review of the survival and growth of tree species planted in degraded peatlands across Southeast Asia to examine (1) species differences, (2) the impact of seedling and site treatments on survival and growth and (3) the potential use of plant functional traits to predict seedling survival and growth rates. Planted seedling monitoring data were compiled through a systematic review of journal articles, conference proceedings, reports, theses and unpublished datasets. In total, 94 study-sites were included, spanning three decades from 1988 to 2019, and including 141 indigenous peatland tree and palm species. Accounting for variable planting numbers and monitoring durations, we analysed three measures of survival and growth: (1) final survival weighted by the number of seedlings planted, (2) half-life, that is, duration until 50% mortality and (3) relative growth rates (RGR) corrected for initial planting height of seedlings. Average final survival was 62% and half-life was 33 months across all species, sites and treatments. Species differed significantly in survival and half-life. Seedling and site treatments had small effects with the strongest being higher survival of mycorrhizal fungi inoculated seedlings; lower survival, half-life and RGR when shading seedlings; and lower RGR and higher survival when fertilising seedlings. Leaf nutrient and wood density traits predicted TPSF species survival, but not half-life and RGR. RGR and half-life were negatively correlated, meaning that slower growing species survived for longer. Synthesis and applications. To advance tropical peat swamp reforestation requires expanding the number and replication of species planted and testing treatments by adopting control vs. treatment experimental designs. Species selection should involve slower growing species (e.g. Lophopetalum rigidum, Alstonia spatulata, Madhuca motleyana) that survive for longer and explore screening species based on functional traits associated with nutrient acquisition, flooding tolerance and recovery from fire.Peer reviewe