High-cycle variable amplitude fatigue experiments and design framework for bridge welds with high-frequency mechanical impact treatment

Fatigue enhancement by way of high-frequency mechanical impact (HFMI) treatment can enable effective design and construction of steel bridges. However, bridges may experience high and varying mean stresses, the effects of which are not covered today by any design recommendation or in the literature on HFMI-treated joints. In this study, fatigue experiments were conducted with realistic in-service bridge loading, which revealed the same high fatigue performance as for constant amplitude loading. The effect of mean stress in spectrum loading was quantified and a method to account for it in an equivalent manner is proposed. A design framework has been developed for design and engineering purposes

Mean Stress Effect in High-Frequency Mechanical Impact (HFMI)-Treated Steel Road Bridges

High-frequency mechanical impact (HFMI) is a post-weld treatment method which substantially enhances the fatigue strength of steel weldments. As such, the method enables a more efficient design of bridges, where fatigue is often the governing limit state. Road bridges are typically trafficked by a large variety of lorries which generate load cycles with varying mean stresses and stress ranges. Unlike conventional welded details, the fatigue strength of HFMI-treated welds is known to be dependent on mean stress in addition to the stress range. The possibility of considering the mean stress effect via Eurocode’s fatigue load models (FLM3 and FLM4) was investigated in this paper. Moreover, a design method to take the mean stress effect into account was proposed by the authors in previous work. However, the proposed design method was calibrated using limited traffic measurements in Sweden, and as such, may not be representative of the Swedish or European traffic. In this paper, larger data pools consisting of more than 873,000 and 446,000 lorries from Sweden and the Netherlands, respectively, were used to examine the validity of the previous calibration in both countries. The comparison revealed no significant difference between the data pools with regards to the mean stress effect. Additionally, the previous calibration provided the most conservative mean stress effect and was considered adequately representative for both countries. The proposed design method was further validated using four composite case study bridges. It was also found that the mean stress effect was mainly influenced by the self-weight, while variation in the mean stress due to traffic had a minor influence on the total mean stress effect. Furthermore, it was found that the mean stress effect could not be accurately or conservatively predicted using FLM3 or FLM4

Knowledge and Attitude of Dental Students and Recent Dental Graduates Towards Dental Pulp Stem Cells in Iran

Objectives Considering the growing knowledge about stem cells and the role of cell-based therapies in the future, dentists should have adequate knowledge about oral stem cell sources and their applications in dentistry. The present study assessed the knowledge and attitude of dental students and recent dental graduates towards dental pulp stem cells (DPSCs) in Iran. Methods This descriptive cross-sectional study was performed in 2021 on 175 participants, including 86 dental students and 89 recent dental graduates from the Dental School of Rafsanjan University of Medical Sciences (RUMS), Rafsanjan, Iran and Dental School of Shahid Beheshti University of Medical Sciences (SBMU), Tehran, Iran. A researcher-designed questionnaire was used to collect data. The validity and reliability of the questionnaire were assessed. The data were analyzed by SPSS version 21 using the Kolmogorov-Smirnov test, independent t-test, and ANOVA. Results The mean knowledge and attitude scores of the participants were 66.16±8.51% and 68.65±11.87%, respectively. The mean attitude score was significantly correlated with “interest in participating in the courses related to stem cells” and “scientific journal review rate”. The level of knowledge of the participants from SBMU was significantly higher than that of participants from RUMS (P<0.05). Other variables did not had a significant effect on the mean score of knowledge or attitude (P>0.05). Conclusion Dental students had a positive attitude towards the application of stem cells; however, their knowledge was inadequate. Therefore, some appropriate measures must be adopted to enhance the knowledge of dental students about DPSCs, especially in universities with lower ranks

Bioethanol production from batch and continuous phytoremediation systems

The effectiveness of water hyacinth (Eichhornia crassipes) in remediating municipal wastewater and producing bioethanol in batch and continuous systems was compared with water lettuce (Pistia stratiotes) and water spinach (Ipomoea aquatica). Batch experiment was conducted using stagnant wastewater system and compared with continuous experiment in order to determine the best treatment system for nutrients and pollutants removal while producing high amount of biomass for bioethanol production. The batch experiment was conducted for 7 days while continuous experiment was conducted for 18 days for each of the aquatic plant. The results for the comparison between rhizofiltration plants have shown that water lettuce has better removal performance compared with water hyacinth and water spinach. The continuous system showed better performance in treatment rate and biomass production compared to batch system. The biomass harvested from water hyacinth, water lettuce and water spinach were 772±37 g/kg, 794±75 g/kg and 702±69 g/kg, respectively. Dinitrosalicyclic test was conducted to measure the reduction of sugar from plant biomass. The concentration of sugar produced by water hyacinth was 21.2±2.7 g/L, while water lettuce was 23.5±3.8 g/L, which was slightly higher than water hyacinth’s sugar production. Water spinach produced the lowest sugar concentration with only 15.5±3.3 g/L. The production of bioethanol estimated from water lettuce was 0.13±0.01 g/g bioethanol. Meanwhile, water hyacinth produced 0.12±0.01 g/g of bioethanol, a value lower than water lettuce. Due to the low concentration of sugar, water spinach managed to produce only 0.10±0.02 g/g bioethanol. In conclusion, water lettuce shows better performance compared with water hyacinth in remediating wastewater and producing biofuel

Cheese tart press machine

Tart is a type of baked open-pastry which consists of a shortcrust pastry and a filling over it (Figure 9.1). Shortcrust pastry often used as the base for the tart. The filling may be usually something sweet and savory poured onto the crust, though modern tarts are usually fruit-based, sometimes with custard. In the production of tart, its crust is the main part. In the process of making tart crust, the dough must first be pressed to get the desired shape and size

Assessment of in-service stresses in steel bridges for high-frequency mechanical impact applications

The application of high-frequency mechanical impact (HFMI) treatment to improve the fatigue performance of composite steel and concrete road bridges was studied through a state-of-the-art review in conjunction with simulations of variable amplitude in-service stresses in four case-study bridges in Sweden. Empirical stress range spectra with associated mean stresses were characterised for HFMI-treated bridges. It was shown that the fatigue-critical locations in HFMI-treated bridges remain unchanged compared with conventional bridges and that compressive overloads pose no detrimental effect that requires additional attention in the fatigue assessment. Calculations also showed a considerably better fatigue performance if HFMI treatment is performed on-site, after the application of self-weight stresses

Mean stress effect in high-frequency mechanical impact (HFMI)-treated welded steel railway bridges

The need for new railway bridges is driven by the growing volume of transportation demands for both passenger and freight traffic on railway networks. In the design of these bridges, the fatigue limit state is a criterion that usually limits the allowable applied load level and thus also the utilization of the high strength of the steel material. Therefore, improving the fatigue performance of welded details by high-frequency mechanical impact (HFMI) treatment leads to a more efficient design. However, the fatigue performance of HFMI-treated welds is known to be affected by the mean stress and this needs to be considered in the design of treated welded details in steel bridges. This is rather straightforward if the bridge is subjected to cycles from one type of train but becomes cumbersome when several different sets of trains (e. g. axle loads, axle distances) cross the bridge. In this article, a factor to take the mean stress effect (including self-weight and traffic load variations) into account is derived from traffic data measured in Sweden. Moreover, the mean stress effect is also predicted using the different fatigue load models in the Eurocode. These models either consist of one-load patterns such as LM71, SW/0, and SW/2 or are composed of different trains with different combinations. It was found that the mean stress effect is underestimated by the first group of models. On the other hand, the mean stress predicted by the light traffic mix is found to be close to that calculated using real traffic data, while other mixes (standard and heavy) underestimate the mean stress effect. Therefore, a correction factor to account for the mean stress effects in real traffic is derived (called here λHFMI). This factor can be used to correct the design stress range for fatigue verification of HFMI-treated welded details in railway bridges

Bioplastics from sweet potatoes

As oil runs out and the use of fossil fuels becomes expensive, the need for replacement source of raw material for the manufacture of plastics becomes essential. Bioplastics are essential as an alternative of commercial plastics from fossil fuels. Bioplastics are eco-friendly and biodegradable hence provide an effective way to replace the commercial plastics. Producing bioplastics from three types of sweet potatoes which are white, orange and purple in colour is the main goal of the study. Extraction techniques were applied to obtain starch from the sweet potatoes. The starch was then mixed with chemical solution such as glycerine, vinegar and distilled water to form bioplastic. The bioplastics were tested for biodegradability, stretch and water adsorption tests. The results show that the bioplastics from white potatoes degrade faster than the other types of sweet potatoes while commercial plastics cannot be degraded at all. White sweet potatoes have less absorption of water which it is the best criteria for bioplastics. Stretchable of white sweet potatoes is more compared to the other types of sweet potatoes. Bioplastics from white sweet potatoes have a good potential as a replacement of commercial plastics

Characterization of the performance of aluminum oxide nanoparticles modified asphalt binder

This study investigates the physical and rheological properties of asphalt binders modified by nano aluminum oxide (AL2O3). Several conventional tests were conducted, including penetration, softening point and ductility, rotational viscosity and dynamic shear rheometer (DSR). Based on the results of the tests, it was found that the hardness of modified asphalt binders increased with the addition of nano AL2O3 up to 5%. As a result of the increased hardness, the softening point of modified asphalt improved compared with base asphalt binders. The rheological property of modified binders was enhanced at low and high temperatures. The results of a DSR test revealed that the G* were improved, whereas the δ decreased slightly. The addition of a different percentage of AL2O3 to base binder had a remarkable influence on resistance to permanent deformation (high temperature rutting and low temperature fatigue). Results recognize 5 wt.% as the optimum content of the modifier. Therefore, nano AL2O3 can be considered as a proper alternative additive to modify the properties of asphalt cement

Epidemiology, risk factors, and co-infection of vector-borne pathogens in goats from Sistan and Baluchestan province, Iran

Several vector-borne pathogens restrict livestock farming and have significant economic impact worldwide. In endemic areas livestock are exposed to different tick species carrying various pathogens which could result in co-infection with several tick-borne pathogens in a single host. Although the co-infection of and the interaction among pathogens are criticalfactors to determine the disease outcome, pathogen interactions in the vector and the host are poorly understood. In this study, we surveyed the presence of Babesia ovis, Theileria ovis, Theileria lestoquardi, Anaplasma ovis, Anaplasma phagocytophilum, and Anaplasma marginale in 200 goats from 3 different districts in Sistan and Baluchestan province, Iran.Species-specific diagnostic PCRs and sequence analysis revealed that 1.5%, 12.5%, and 80% of samples were positive for T. lestoquardi, T. ovis, and A. ovis, respectively. Co-infections of goats with up to 3 pathogens were seen in 22% of the samples. We detected a significant association between T. ovis infection and age, T. ovis infection and location (Zabol), and A. ovis infection and location (Sarbaz) by multivariate logistic regression analysis. In addition, by analyzing the data with respect to Plasmodium caprae infection in these goats,a negative correlation was found between P. caprae and A. ovis infection. This study contributes to understanding the epidemiology of vector-borne pathogens and their interplay in goats