Predicting the airborne microbial transmission via human breath particles using a gated recurrent units neural network

Purpose The purpose of this paper is to devise a tool based on computational fluid dynamics (CFD) and machine learning (ML), for the assessment of potential airborne microbial transmission in enclosed spaces. A gated recurrent units neural network (GRU-NN) is presented to learn and predict the behaviour of droplets expelled through breaths via particle tracking data sets. Design/methodology/approach A computational methodology is used for investigating how infectious particles that originated in one location are transported by air and spread throughout a room. High-fidelity prediction of indoor airflow is obtained by means of an in-house parallel CFD solver, which uses a one equation Spalart–Allmaras turbulence model. Several flow scenarios are considered by varying different ventilation conditions and source locations. The CFD model is used for computing the trajectories of the particles emitted by human breath. The numerical results are used for the ML training. Findings In this work, it is shown that the developed ML model, based on the GRU-NN, can accurately predict the airborne particle movement across an indoor environment for different vent operation conditions and source locations. The numerical results in this paper prove that the presented methodology is able to provide accurate predictions of the time evolution of particle distribution at different locations of the enclosed space. Originality/value This study paves the way for the development of efficient and reliable tools for predicting virus airborne movement under different ventilation conditions and different human positions within an indoor environment, potentially leading to the new design. A parametric study is carried out to evaluate the impact of system settings on time variation particles emitted by human breath within the space considered.

An Experimental Study on External Ventilation to the Heating Performance of Household Air Source Heat Pump

The external ventilation conditions have a great influence on the heating performance of the air source heat pump (ASHP) systems. The outdoor units of residential household air source heat pumps are often installed in narrow spaces such as balconies. The ventilation conditions of the outdoor unit will influent the heating performance of the air source heat pump. It is necessary to study the effect of the outdoor unit ventilation conditions on the heating performance of residential household heat pumps. This paper experimentally studied the heating performances of an air source heat pump system with the outdoor unit mounted in a balcony in different external ventilation conditions. The results indicate that the ventilation conditions for the outdoor units have a significant effect on the heating performance of the system. When the inlet of the outdoor unit was close to the sliding door and completely blocked, the ventilation environment was the worst and the coefficient of performance (COP) was the lowest. In addition, the unfavorable ventilation environment could result in a reduction of the COP by 26.2%. When the inlet of the outdoor unit was partially blocked, the heating performance could be improved and the COP was also slightly improved. The great heating performance was obtained under the cross-ventilation condition. This paper can guide the design of the installation position of the household air source heat pump outdoor units in actual engineering.

Effect of factors on growth and development of Dendrobium officinale Kimura et Migo cultured in vitro and ex vitro

Dendrobium officinate Kimura et Migo, a species of orchid for beautiful flowers, is used in traditional medicine in many Asian countries because there are many important pharmaceuticals (chrysotoxene, erianin, confusarin, polysaccharide, alkaloid ...) in anti-cancer, anti-aging, boosting immunity and vasodilation, etc. In recent years, more than 4,000 hectares of Dendrobium officinate Kimura et Migo artificial planting has been available in China and the price of dry product was around ¥ 80,000/kg. Currently, plantlet quality is an important factor influencing the acclimatization stage, growth, and development of plants in the greenhouse. In this study, the effect of a number of factors medium, plant regulator, ventilation, and substrate to improve plantlet quality as well as further growth and development in the greenhouse conditions were investigated. The results showed that SH medium was suitable for in vitro shoot growth in terms of monitoring parameters after 90 days of culture. In shoot multiplication stage, the shoots culture on SH medium supplemented with 2 mg/L BA, 30 g/L sucrose, 9 g/L agar, 1g /L activated charcoal (AC) gave the best results with 4.53 shoots/per shoot. The SH medium supplemented with 1.0 mg/L NAA, 30 g/L sucrose, 9 g/L agar, 1.0 g/L AC combined with ventilation conditions was suitable for rooting stage with plant height (5.73 cm), number of roots (4.77), root length (5.00 cm), fresh weight (3.36 g), dry weight (0,31 g), and total chlorophyll (SPAD) (45.76 nmol/cm2). Plantlets derived from culture ventilation conditions cultivated on the mixture of pine bark and fern fiber (50:50) was the highest survival rate (100%) and growth after 12 months in the greenhouse.

Microclimatic and Ventilation Conditions in Existing Healthcare Facilities. A Study in the Waiting Room-Testing Centre of a Florentine Historic Hospital

The pandemic COVID-19 era we are experiencing has changed our way of seeing, thinking and designing indoor and outdoor environments and, above all, plant systems and building-plant management. Energy environmental sustainability is a common fundamental target for buildings and plant systems, but health protection and prevention are the priority issues for the basis of any retrofitting and refurbishment operation. This question becomes even more complex if the building is historic and used for hospital or for healthcare facilities. In this research we propose a methodological approach based on the combination of physical-real and “virtual”, i.e. measured and simulated information. The proposed method can be a useful tool for setting up continuous monitoring systems for microclimatic and ventilation conditions, user influx/presence and behaviour, real operation (on demand) of the plants and control/regulation system adjustment. Results show the importance of drawing up useful guidelines for training health workers and people/patient subjects, aiming at conscious interaction for health and wellbeing protection, but also better indoor environment management. This is particularly important for healthcare environments such as the one studied.

The comfort parameters in indoor air of sports facilities with different ventilation regimes

Introduction: In Portugal, during COVID19pandemic, sport and fitness facilities were closed. When lockdown has been lifted, in order to prevent the spread of infection, indoor sport facilities were subject to specific regulations that limited indoor occupancy as well as manner of air ventilation. This study aims to analyze the impacts of these ventilation restrictions on indoor air comfort parameters in sport fitness facilities. Methodology: Temperature (T; ºC), relative humidity (RH; %), and carbon dioxide (CO2) were continuously monitored (41 days; spring and autumn) in four fitness centers situated in Oporto metropolitan area: two of them under normal ventilation conditions (i.e. before lockdown; NV1 and NV2) and two of them under temporary restrictions for indoor ventilations and occupancy (RV1 and RV2). Results and Discussion: Under normal ventilation conditions, T in fitness centers slightly varied (in NV1:22-25 ºC; NV2: 20-23 ºC) but in both clubs the comfort recommendations (18-25 ºC) were fulfilled. On contrary, RH were below guideline values (55-75%) in NV1 (47-54%) whereas at NV2 (66-73%) it fulfilled the recommendations. When specific health regulations took place, mean T ranges were similar in both clubs (RV1: 21-23 ºC; RV2:21-23 ºC) but they both exceeded recommended comfort levels (16-21 ºC). Mean RH were in accordance with the legislative values, but the very high temporal maxima (up to 75 and 89%) indicate the possible discomforts the that exercisers might have experienced. Concerning the CO2, the obtained results showed that indoorlevels decreased when specific health restrictions were in force (11-121%) most likely due imposed guidelines for human occupancy. Conclusions: The restrictions for ventilation and human occupancy positively impacted indoor levels of CO2. However, T and RH were on several occasions outside the recommended comfort levels, especially during group activity classes. As regular exercising in environmental conditions, such as elevated T and increased RH can cause health discomforts, these parameters should be carefully maintained within the recommended ranges even under restricted ventilation scenarios.