Computational mathematics applied in the identification of the risk of indirect contagion of COVID-19 in university classrooms

This exploratory study evaluated the risk of contagion from airborne diseases, such as coronaviruses, in schools. For three days, the concentration of carbon dioxide in two university classrooms was monitored for 90 minutes, while the students took their math classes. We use these values to validate a first-order model for carbon dioxide concentration and calculate the air exchange rate indirectly (avoiding the need for expensive measurement equipment). The air exchange rate obtained allowed us to assess whether the usual ventilation systems (both natural and mechanical) are sufficient to guarantee a low risk of contagion of aerosols due to respiration. The results show that the risk of contagion is low if three factors are considered: the level of conversation within the classroom, the usage of a moisture extraction system, and the lecture duration. The risk is low if the lecture time is less than 50 minutes, the level of conversation is moderate, and a moisture extraction system is available. If these conditions are not met the risk is considerably higher even if mechanical ventilation is employed.

Estimating Moisture Content of Sausages with Different Types of Casings via Hyperspectral Imaging in Tandem with Multivariate

The moisture levels in sausages that were stored for 16 days and added with different concentrations of orange extracts to a modification solution were assessed using response surface methodology (RSM). Among the 32 treatment matrixes, treatment 10 presented a higher moisture content than that of treatment 19. Spectral pre-treatments were employed to enhance the model's robustness. The raw and pre-processed spectral data, as well as moisture content, were fitted to a regression model. The RSM outcomes showed that the interactive effects of [soy lecithin concentration] × [soy oil concentration] and [soy oil concentration] × [orange extract addition] on moisture were significant (p < 0.05), resulting in an R2 value of 78.28% derived from a second-order polynomial model. Hesperidin was identified as the primary component of the orange extracts using high-performance liquid chromatography (HPLC). The PLSR model developed from reflectance data after normalization and 1st derivation pre-treatment showed a higher coefficient of determination in the calibration set (0.7157) than the untreated data (0.2602). Furthermore, the selection of nine key wavelengths (405, 445, 425, 455, 585, 630, 1000, 1075, and 1095 nm) could render the model simpler and allow for easy industrial applications.

Modification of the Aeration-Supplied Configuration in the Biodrying Process for Refuse-Derived Fuel (RDF) Production

Biodrying is an essential part of the mechanical–biological treatment process that minimizes moisture content and simultaneously maximizes heating value for refuse-derived fuel (RDF) production. Although the mechanical separation process operates effectively in Thailand's RDF production, high organic content levels and their degradation cause moisture contamination in RDF, producing wet RDF. Aeration is essential for an effective biodrying process, and can reduce RDF's moisture content as well as increase its heating value. To maximize the biodrying effect, aeration should be optimized based on the waste conditions. This study proposes a modified aeration-supplied configuration for wet RDF biodrying. The aeration rate was modified based on the period within the biodrying operation;the first period is from the beginning until day 2.5, and the second period is from day 2.5 to day 5. The optimal aeration supply configuration was 0.5 m3/kg/day in the first period and then 0.3 m3/kg/day until the end of the process;this configuration yielded the greatest moisture content decrease of 35% and increased the low heating value of the biodried product by 11%. The final moisture content and low heating value were 24.07% and 4787 kcal/kg, respectively. Therefore, this optimal aeration-supplied configuration could be applied to meet the moisture content and low heating value requirements of the RDF production standard for Thailand's local cement industry.

Application of GIS-Based AHP Model for the Impact Assessment of COVID-19 Lockdown on Environment Quality: The Case of Kabul City, Afghanistan

The COVID-19 pandemic has negatively impacted the industrial, financial, and social aspects of our daily life due to the implementation of lockdown to protect against the spread of the virus. In addition, the lockdown deduced by COVID-19 has promising positive impacts on air quality and environmental pollution. This study aims to monitor the effects of lockdown on environmental degradation during the pandemic in Kabul city, the capital of Afghanistan, using geospatial data and a statistical model of the Analytical Hierarchy Process (AHP). To achieve the purpose of the study, the most essential influencing factors on air quality were generated from different sources using Google Earth Engine (GEE) and GIS environment;Normalized Difference Vegetation Index (NDVI), Normalized Difference Water Index (NDWI), Normalized Difference Moisture Index NDMI) were calculated using Sentinel-2MSI, Carbon Monoxide (CO) was obtained from Sentinel-5P TROPOMI, and land surface temperature was retrieved from MODIS data. The generated thematic layers (before COVID-19, and during a lockdown of COVID-19) were weighted and rated using the AHP analysis. The weighted layers were spatially overlayed to obtain the final output. Consequently, the environmental quality degradation maps before and during COVID-19 were generated to assess the differences over the 22 districts of Kabul city. The findings of the study show that Kabul city is covered by the very low, low, moderate, high, and very high degradation of the environment by 3.17%, 5.33%, 20.54%, 26.63%, 44.32% before COVID-19 in 201,9 respectively, while the percentages are changed to 4.37%, 8.99%. 16.55%, 37.47%, and 32.62% during the lockdown caused by COVID-19 in 2020. The changes in the percentage of environmental degradation in Kabul city particularly in high and very high zones confirm the positive impact of the lockdown of COVID-19.

Mutual Effects of Zinc Concentration and Ratio of Red-Blue Light on Growth and Nutritional Quality of Flowering Chinese Cabbage Sprouts

The nutritional quality and biomass of various sprouts can be enhanced by Zn and red-blue light, especially the Brassica sprouts. However, the combined effects of this two on sprouts are rarely reported. In this study, different Zn concentrations (0, 1.74, 3.48, 10.43 and 17.39 mM) were combined with two ratios of red-blue light-emitting diodes (LEDs) (R: B = 1:2, 1R2B;R: B = 2:1, 2R1B, at 70 μmol m−2 s−1 PPFD, 14 h/10 h, light/dark) to investigate their mutual effects on the growth, mineral elements, and nutritional quality in flowering Chinese cabbage sprouts (FCCS). Fresh weight, dry weight, contents of organic Zn, soluble sugar, vitamin C, total flavonoids, total polyphenol, FRAP (ferric ion-reducing antioxidant power) and DPPH (radical inhibition percentage of 1,1-diphenyl-2-picrylhydrazyl) were significantly increased by Zn supplement (10.43 and 17.39 mM) and 2R1B, while hypocotyl length and moisture content were decreased remarkably by Zn supplement. Total glucosinolates contents in the sprouts increased dramatically under 2R1B compared with 1R2B, while photosynthetic pigments contents decreased. Heat map and principal component analysis showed that 2R1B + 17.39 mM Zn was the optimal treatment for the accumulation of biomass and health-promoting compound in FCCS, suggesting that a suitable combination of light quality and Zn supplement might be beneficial to zinc-biofortified FCCS production.

Evaluation on the use of COVID-19 single-use face masks to improve the properties of hot mix asphalt

With the outbreak of the coronavirus (COVID-19) and the spread of this virus, the use of medical equipment, like 3-layerface masks, has increased dramatically. The proliferation of polymer-based face masks has become an environmental problem as ittakes years to completely decompose. The lack of proper management and collection causes environmental pollution. Therefore,considering the polymer base of the face masks and with the aim of improving the asphalt mixtures, in this article, the face mask andits different layers are added to the asphalt mixtures in 4 different weight percentages and in two different sizes, and Marshall test,Resilient modulus, Indirect tensile, Moisture damage, Rutting and Fatigue test were performed on the samples. The experimentalresults show that the addition of these materials to the asphalt mixtures improves the performance of asphalt and 12mm long fibersyielded better results than the results of 8mm long fibers.

Strength Characteristics and Failure Mode of Solidified Soil Reinforced by Waste Masks

COVID-19 prevention and control consumed a large number of disposable masks,which had a large amount of waste disposal and high environmental protection requirements. It is one of the important methods to solve the problems of difficult source and high price of high-quality subgrade fillers. This paper proposes the solution of used waste masks to reinforce sludge solidified soil with high moisture contents,which will be used as subgrade fillers,with cement as curing agents and waste masks as reinforcing materials,the unconfined compressive resistance of waste mask reinforced cement solidified soil under different waste mask contents,mask sizes and ages is measured,additionally,the influences of the mask sizes and ages on the reinforcement effect of cement solidified soil are discussed,and this study also analyze the influence of reinforcement of waste mask on the failure modes of cement solidified soil. The results show that,under the experimental conditions,the optimum content of waste mask is about 0.5%,and the unconfined compressive strength is increased by about 87.5%.The stress-strain curve of unconfined compressive strength of cement-solidified soil reinforced with waste masks shows a softening pattern,and the reinforcement of waste mask improves the deformation resistance of the sample. The cement-solidified soil reinforced with waste masks presents a certain plastic failure characteristic.

Polymer Membranes for Enthalpy Exchangers

A membrane-based enthalpy exchanger is a device used for heat and humidity recovery in ventilated buildings. The energy-saving potential of such a device is dependent on the parameters responsible for heat and moisture recovery. The trend is toward composite membranes, which are custom produced, and their parameters can be adjusted for a given application;therefore, the diffusion and sorption characteristics of such membranes are unknown. In order to obtain the values of the water vapor diffusivity of three investigated handmade membranes, a serial resistance model using a Field and Laboratory Emission Cell (FLEC) is proposed. Experiments were conducted to identify the resistance in each step of the moisture transfer process to extract the moisture diffusivity in the membranes. The calculated moisture diffusivities in the membranes were 8.99 × 10−12 (m2/s) for the membranes from cellulose acetate, 1.9 × 10−10 (m2/s) for the microporous PE/PUR membranes, and 1.53 × 10−11 (m2/s) for the PET/PUR microfibrous membranes. The obtained membrane diffusivities were then used in the proposed effectiveness-NTU-based model of an exchanger with a cross-flow arrangement to predict performance under various operating conditions. The results show that the highest latent effectiveness was found for the exchanger core made from the PE/PUR membrane and the lowest was for the one with the PE/PUR membrane core.

Evaluation of Hesperidin on Sausages Stuffed in a New Modified Casing during Long-Term Storage—A Preliminary Study

The effects of hesperidin and different casings on pH, moisture content, water-holding capacity, and total viable count (TVC) of sausages stored for 171 days were evaluated by principal component analysis (PCA) and discriminant analysis (DA). Sausages stuffed in a modified casing with treatment B (soy lecithin concentration: 1:30, soy oil concentration: 2.5%, lactic acid concentration: 21 mL/kg NaCl [solid], treated time: 90 min) had a significantly lower pH value (6.89 ± 0.01) at d 31 but higher (6.55 ± 0.03) than that of control casings at d 171 (p < 0.05). Hesperidin plays an important role in antimicrobial property that renders the sausages with modified casing by treatment A (soy lecithin concentration: 1:27.5, soy oil concentration: 1.25%, lactic acid concentration: 19.5 mL/kg NaCl [solid], treated time: 75 min) stable (p > 0.05), with the final TVC of 5.03 ± 0.10 log cfu/g. According to the PCA results, water-holding capacity has a positive correlation to pH. Moisture content was the best discriminator for differentiating sausages with control and modified casings, whilst pH was able to discriminate sausages stored after 138 days from other days.

Assessing Barriers in Adaptation of Water Management Innovations under Rotational Canal Water Distribution System

This study assessed problems associated with irrigation water provisions and the potential barriers to the adaptation of the interventions (soil moisture sensors, on-farm water storage facilities and the drip method) under rotational canal water distribution in Punjab, Pakistan. Three groups of stakeholders were individually surveyed during September–December 2020: (i) 72 farmers, (ii) 15 officials, and (iii) 14 academicians. We used descriptive statistical analysis, cross-tabulation and the Fisher test to explore the pattern of responses across the groups. The main problems in the canal water distribution system were expressed by the farmers as limited water allocation, while academicians were concerned mostly with inflexibility and officials indicated discussion among neighbors. According to the farmers’ responses, the conventional depth/interval of irrigation is flooding the field with water and observing the plants, indicating over-irrigation behavior. Moreover, the most important barriers in the adaptation of the interventions that were highly rated by the three groups were low awareness, lack of training and financial resources. Additionally, farmers’ education revealed a statistically significant influence on awareness of soil moisture sensors and water storage facilities, while large farm holders showed a positive relationship to conducting a joint experiment with scientists and farmers’ associations on part of their land to improve water use efficiency.

Preparing and Characterizing Novel Biodegradable Starch/PVA-Based Films with Nano-Sized Zinc-Oxide Particles for Wound-Dressing Applications

Given recent worldwide environmental concerns, biodegradability, antibacterial activity, and healing properties around the wound area are vital features that should be taken into consideration while preparing biomedical materials such as wound dressings. Some of the available wound dressings present some major disadvantages. For example, low water vapor transmission rate (WVTR), inadequate exudates absorption, and the complex and high environmental cost of the disposal/recycling processes represent such drawbacks. In this paper, starch/polyvinyl alcohol (PVA) material with inserted nano-sized zinc-oxide particles (nZnO) (average size ≤ 100 nm) was made and altered using citric acid (CA). Both ensure an efficient antibacterial environment for wound-dressing materials. The film properties were assessed by UV–Vis spectrometry and were validated against the UV light transmission percentage of the starch/ polyvinyl alcohol (PVA)/ zinc-oxide nanoparticles (nZnO) composites. Analyses were conducted using X-ray Spectroscopy (EDX) and scanning electron microscopy (SEM) to investigate the structure and surface morphology of the materials. Moreover, to validate an ideal moisture content around the wound area, which is necessary for an optimum wound-healing process, the water vapor transmission rate of the film was measured. The new starch-based materials exhibited suitable physical and chemical properties, including solubility, gel fraction, fluid absorption, biodegradability, surface morphology (scanning electron microscopy imaging), and mechanical properties. Additionally, the pH level of the starch-based/nZnO film was measured to study the prospect of bacterial growth on this wound-dressing material. Furthermore, the in vitro antibacterial activity demonstrated that the dressings material effectively inhibited the growth and penetration of bacteria (Escherichia coli, Staphylococcus aureus).