Ventilation System Operation to Minimize the COVID-19 Airborne Transmission in Schools

Minimizing the SARS-CoV-2 virus transmission is essential to face the COVID-19 pandemic. This is even more important for highly crowded indoor environments, e.g. schools, where the mitigation solutions based on social distancing and hand washing seem to be not effective to reduce the virus airborne transmission mode, which is the main route of transmission. To minimize the airborne virus transmission a proper ventilation is necessary. In the study, a simplified mass balance equation (box-model) was applied to school scenarios in order to determine the required conditions to maintain the infection risk below an acceptable level. In particular, the required air exchange rates for mechanically-ventilated classrooms and the adequate airing procedures for naturally ventilated classrooms were determined. Moreover, for naturally ventilated classrooms, a control strategy based on the measurement of CO2 indoor concentration was also developed.

Analysis of Selected Methods Use for Calculation of the Coefficients of Adsorption Isotherms and Simplified Equations of Adsorption Dynamics with the Use of IZO Application

The purpose of this paper is to present the IZO application that calculates and visualizes coefficients of adsorption isotherms according to Freundlich, Langmuir, and BET in a classic and linear system, in a simple communicative way. The application also calculates the working time of the adsorption bed based on the transformation of the mass balance equation, and according to the Zuchowicki, Zabieziński, Tichonow, and the Bohart-Adams equations. The laboratory tests of the adsorption process of leachate from a municipal landfill on selected active coals ORGANOSORB 10, DESOTEK, and BA-10, were conducted to check the program for accuracy. Results of tests confirm that the linearization method of the calculation of adsorption isotherms coefficients, used in the IZO application, gives sufficient accuracy and may be used as an alternative of, e.g., the nonlinear estimation method.

Effect of the Boron Powder on Surface AISI W2 Steel: Experiments and Modelling

The effect of boron powder on surface AISI W2 steel and growth kinetic of the boride layer is studied. Boron powder mixture was used in the powder pack boriding; this process was carried out in the temperature range from 1173 to 1273 K with exposure times ranging from 2 to 8 h. The presence of boride was confirmed by optical microscopy, X-ray diffraction, and the distribution of alloy elements in boride layers with energy-dispersive spectrometry using scanning electron microscopy. A mathematical model of the growth kinetics of the single layer was proposed and boron diffusion coefficient was determined by mass balance equation. The morphology of Fe2B layer was smooth and boron activation energy in W2 steel was estimated as 187.696 kJ·mol−1. The kinetic model was validated with two experimental conditions, a contour diagram describing the evolution of Fe2B layer as a function of time and temperature parameters for industrial application.

Validating The Core Concept Of “Mass Balance”

We have created a conceptual framework for the core concept of “mass balance.” Unlike the previous conceptual frameworks that we have created and validated, the framework for “mass balance” is simply a description in words of the fundamental mass balance equation and the implications of the equation. We surveyed physiology faculty and asked them to rate the importance of “mass balance” as defined by the conceptual framework and also to rate the importance for their students of being able to apply the core concept to liquids, gases, solutes, and solids. Respondents indicated that “mass balance” is important and that our conceptual framework provides a useful tool for teaching and learning. We discuss several examples of how “mass balance” can be used in making sense about a variety of physiological phenomena.

Estimasi Jumlah Penghuni Ruangan Berdasarkan Konsentrasi CO2 Dengan Metode Bayesian MCMC

<span lang="PT-BR">The number of occupants in the building is important information for building management because it is related to security issues, evacuation, and energy saving. This article focuses on estimating the number of occupants using the Bayesian Monte Carlo Markov chain (MCMC) method based on indoor CO₂ levels. Probability theory underlies the Bayesian MCMC principle, where the mass balance equation of indoor CO₂ is used as a physical model of estimation calculations. Determination of the variables in the mass balance equation is investigated to obtain the effect on the accuracy of the estimated number of occupants. It found that the higher the standard deviation of the input variable on the physical model, the higher the error estimation produced. In addition, the Bayesian MCMC algorithm is tested in a real-time scheme of test</span><span lang="IN">-</span><span lang="PT-BR">chamber. The result shows an estimated error of 39%. Rapid changes influence estimation errors in actual occupants relative to the sample interval and the time delay of the estimation.</span>

Simulation of boronizing kinetics of ASTM A36 steel with the alternative kinetic model and the integral method

In this study, two different mathematical models have been proposed for estimating the diffusivities of boron in the Fe2B layer on ASTM A36 steel in the range of 1173 to 1273 K with exposure times of 2 to 8 h. The boride incubation period required for the formation of such a layer was constant regardless of the boriding conditions. In both approaches, the boron diffusivity in the iron phase was considered in an unsaturated matrix. The first approach was derived from the mass balance equation at the (Fe2B/substrate) interface while the second approach employed the integral diffusion model. The calculated values of boron activation energies for ASTM A36 steel were found to be very comparable for the two approaches (161.65 and 160.96 and kJ mol-1). Afterwards, these values of activation energy were confronted with the results from the literature. Experimental validation of these two approaches has been done by comparing the experimental value of Fe2B layer thickness measured at 1123 K for 2.5 h with the simulated values. Finally, the predicted values of Fe2B layer thickness were in line with the experimental measurement.

Selection of air filters for residential fresh air in china based on the control of PM2.5

Efficient filtration provides a healthy and comfortable residential environment. Based on the performance testing for filter materials commonly used in China, the mass balance equation of controlling the indoor PM2.5 concentration was set up, and the filter selection criterion was discussed. An optimal section was suggested by taking into account the economic cost, filter price, and indoor air quality.

Pemodelan Kesetimbangan Massa pada Keadaan Tunak (Steady) sebagai Penentuan Konsentrasi Optimum Tawas (Alumunium Sulfate) pada Proses Penurunan Kadar Fe pada Sumber Air Tercemar

Air tanah merupakan andalan sumber mata air bagi masyarakat pada umumnya, beberapa sumber air tanah sering dijumpai air yang masih terkandung Fe, hal tersebut berdampak buruk bagi kesehatan oleh karena itu perlu dilakukan penuruan kadar Fe pada air sebelum digunakan. Beberapa metode yang umum dilakukan untuk menghilangkan kandungan Fe pada air adalah dengan cara koagulasi oleh tawas. Penelitian ini akan memodelkan sebuah persamaan matematika yang dapat mengkuantifikasi penurunan kadar Fe pada setiap fungsi kosentrasi tawas yang ditambahkan. Model matematika pada penelitian menggunakan penurunan rumus dari kesetimbangan masa. Dari hasil perbandingan data percobaan dengan data perhitungan didapat konstanta penurunan Fe (kF) pada fungsi konsentrasi tawas sebesar 1.8/mg tawas dan nilai konstanta R2 sebesar 0.935, dari data tersebut maka model matematika yang dibuat dapat mewakili fenomena proses penurunan Fe di lapangan.In general groundwater is relied as source water but somtimes we found precense of Fe in some of groundwater products that could harm our health due to its toxicity, therefore it is necessary to reduce Fe content as pretreatment process. Some common methods to reduce Fe content in water are coagulation by alum. This study will build a mathematical equation to quantify the reduction of Fe content in function of alum concentration. In this study the equations were derive from mass balance equation. By comparing the experimental data with calculated data, we obtained kF (The constant of consuming Fe) = 1.8 / mg alum and for R2 constant we obtained 0.935, from these result we conclude our derived equation can represent the phenomenon of alum-Fe reduction phenomena in the field.