scholarly journals Natural Ventilation Characterization in a Classroom under Different Scenarios

2021 ◽  
Vol 18 (10) ◽  
pp. 5425
Author(s):  
Sergio A. Chillon ◽  
Mikel Millan ◽  
Iñigo Aramendia ◽  
Unai Fernandez-Gamiz ◽  
Ekaitz Zulueta ◽  
...  
Keyword(s):  
Particle Size ◽  
Relative Humidity ◽  
Natural Ventilation ◽  
Particle Diameter ◽  
Co2 Concentration ◽  
Median Particle Diameter ◽  
Surgical Masks ◽  
Computer Classroom ◽  
Median Particle ◽  
Carbon Dioxide Co2

The COVID-19 pandemic has pointed to the need to increase our knowledge in fields related to human breathing. In the present study, temperature, relative humidity, carbon dioxide (CO2) concentration, and median particle size diameter measurements were taken into account. These parameters were analyzed in a computer classroom with 15 subjects during a normal 90-minute class; all the subjects wore surgical masks. For measurements, Arduino YUN, Arduino UNO, and APS-3321 devices were used. Natural ventilation efficiency was checked in two different ventilation scenarios: only windows open and windows and doors open. The results show how ventilation affects the temperature, CO2 concentration, and median particle diameter size parameters. By contrast, the relative humidity depends more on the outdoor meteorological conditions. Both ventilation scenarios tend to create the same room conditions in terms of temperature, humidity, CO2 concentration, and particle size. Additionally, the evolution of CO2 concentration as well as the particle size distribution along the time was studied. Finally, the particulate matter (PM2.5) was investigated together with particle concentration. Both parameters showed a similar trend during the time of the experiments.

Influences of Microemulsion Cross-linking Reaction and Ball-milling on Particle Size Characteristics of Potato and Maize Starches

2006 ◽  
Vol 2 (4) ◽  
Author(s):  
Yu-guang Zhou ◽  
Dong Li ◽  
Li-jun Wang ◽  
Necati Özkan ◽  
Xiao Dong Chen ◽  
...  
Keyword(s):  
Particle Size ◽  
Ball Milling ◽  
Surface Area ◽  
Potato Starch ◽  
Particle Diameter ◽  
Cross Linking ◽  
Maize Starch ◽  
Median Particle Diameter ◽  
Mean Diameter ◽  
Median Particle

In this study, microemulsion cross-linking treatment was used on food grade potato and maize starches for preparing micro starch particles. Laser diffraction technique was introduced to measure the particle size characteristics, including the median particle diameter (d 50), surface area mean diameter D [3, 2], volume mean diameter D [4, 3] and specific surface area of micro potato and maize starch particles. The volume distributions and number distributions were also analyzed using Mastersizer 2000 Software. The d 50, D [3, 2], D [4, 3] of the potato starch granules were reduced significantly (p < 0.05) after the microemulsion cross-linking reaction and ball-milling treatment. However, the microemulsion cross-linking treatment did not produce significant changes in the particle size characteristics of the maize starch samples.

The intertidal macrofauna of Nigg Bay

1986 ◽  
Vol 91 ◽  
pp. 113-141
Author(s):  
D. Raffaelli ◽  
P. R. Boyle
Keyword(s):  
Particle Diameter ◽  
Detrended Correspondence Analysis ◽  
Distribution Patterns ◽  
Trophic Levels ◽  
Median Particle Diameter ◽  
Moray Firth ◽  
Median Particle ◽  
Biological Characters ◽  
Rich Fauna ◽  
Factor Governing

SynopsisSurveys of the intertidal macrofauna and sediment characters of Nigg Bay, Moray Firth, were carried out between 1981 and 1985. Permanent stations were located at the intersections of a half-kilometre grid covering the entire intertidal area and sampled for infauna, using replicate cores. Estimates were also made of mussel and lugworm densities from quadrats and cast counts respectively. The biomasses of selected species that constitute important resources for higher trophic levels were also estimated. The sediment for each station was analysed for median particle diameter and silt content.The infaunal data were analysed by Detrended Correspondence Analysis. This indicated that tidal height was the most important factor governing the distribution and abundance of the intertidal communities. Sediment characters were only poorly related to distribution patterns.The bay has a rich fauna and is biologically similar to other outer bays of the Moray Firth, which, like Nigg, are important areas for wildfowl and waders. Comparisons of survey data from different years indicate that there are natural cycles in some sediment and biological characters of Nigg Bay.

scholarly journals Monitoring and Assessment of Indoor Environmental Conditions after the Implementation of COVID-19-Based Ventilation Strategies in an Educational Building in Southern Spain

Sensors ◽  
2021 ◽  
Vol 21 (21) ◽  
pp. 7223
Author(s):  
Antonio J. Aguilar ◽  
María L. de la Hoz-Torres ◽  
Mª Dolores Martínez-Aires ◽  
Diego P. Ruiz
Keyword(s):  
Relative Humidity ◽  
Natural Ventilation ◽  
Co2 Concentration ◽  
Quality Level ◽  
Indoor Environmental Quality ◽  
Effective Measure ◽  
Acoustic Environment ◽  
Health Authorities ◽  
Ventilation Strategies ◽  
Ventilation Rates

Since students and teachers spend much of their time in educational buildings, it is critical to provide good levels of indoor environmental quality (IEQ). The current COVID-19 pandemic has shown that maintaining a good indoor air quality level is an effective measure to control the transmission of the SARS-CoV-2 virus. This study used sensors to monitor key IEQ factors and assess several natural ventilation scenarios in a classroom of the University of Granada. Subsequently, the IEQ factors (temperature, relative humidity, CO2 concentration, acoustic environment, and air velocity) were evaluated for the selected ventilation scenarios in the occupied classroom, and the field monitoring was carried out in two different assessment periods, winter and summer. The obtained results show that the CO2 concentration levels were well below the recommended limits. However, the maintenance of the recommended thermal and acoustic IEQ factors was significantly affected by the natural ventilation strategies (temperature and relative humidity values were very close to the outside values, and the background sound pressure level was over 35 dBA during the entire assessment). The proper measurements and careful selection of the appropriate ventilation scenarios become of utmost importance to ensure that the ventilation rates required by the health authorities are achieved.

The Intrusion of Fine Sediments into a Stable Gravel Bed

1979 ◽  
Vol 36 (2) ◽  
pp. 204-210 ◽  
Author(s):  
Robert L. Beschta ◽  
William L. Jackson
Keyword(s):  
Sediment Transport ◽  
Pore Space ◽  
Particle Diameter ◽  
Experimental Tests ◽  
Gravel Bed ◽  
Fine Sediments ◽  
Median Particle Diameter ◽  
Key Words Sediment ◽  
Median Particle ◽  
Flow Variables

A rectangular flume was used to study variables affecting the intrusion of fine sands into a stable gravel streambed. The amount of intrusion by sand (median particle diameter 0.5 mm) was determined under varied conditions of discharge, depth, velocity, flume slope, and rates of sediment transport. During all experimental tests, sand particles were trapped in voids within the upper 10 cm of an initially clean gravel bed (median particle diameter 15 mm), forming a barrier to further intrusion. An analysis of flow variables showed that flow conditions, as indexed by Froude number, significantly (90% confidence level) affected intrusion amounts, possibly by influencing the rate and depth of formation of the sand seal. Intrusion amounts, expressed as a percent of total volume, varied from 2 to 8%. Two replications used a finer grade sand (median particle diameter 0.2 mm) that intruded more and, in one case, completely filled the gravel pore space (25% by volume), further indicating that particle size, and not hydraulic variables, may have a more important influence on the total amount of intrusion. Key words: sediment transport, intrusion, streambed, substrates, riffles, sedimentation

An expert system with radial basis function neural network based on decision trees for predicting sediment transport in sewers

2016 ◽  
Vol 74 (1) ◽  
pp. 176-183 ◽  
Author(s):  
Isa Ebtehaj ◽  
Hossein Bonakdari ◽  
Amir Hossein Zaji
Keyword(s):  
Neural Network ◽  
Expert System ◽  
Sediment Transport ◽  
Radial Basis Function ◽  
Decision Trees ◽  
Basis Function ◽  
Particle Diameter ◽  
Median Particle Diameter ◽  
Radial Basis ◽  
Median Particle

In this study, an expert system with a radial basis function neural network (RBF-NN) based on decision trees (DT) is designed to predict sediment transport in sewer pipes at the limit of deposition. First, sensitivity analysis is carried out to investigate the effect of each parameter on predicting the densimetric Froude number (Fr). The results indicate that utilizing the ratio of the median particle diameter to pipe diameter (d/D), ratio of median particle diameter to hydraulic radius (d/R) and volumetric sediment concentration (CV) as the input combination leads to the best Fr prediction. Subsequently, the new hybrid DT-RBF method is presented. The results of DT-RBF are compared with RBF and RBF-particle swarm optimization (PSO), which uses PSO for RBF training. It appears that DT-RBF is more accurate (R2 = 0.934, MARE = 0.103, RMSE = 0.527, SI = 0.13, BIAS = −0.071) than the two other RBF methods. Moreover, the proposed DT-RBF model offers explicit expressions for use by practicing engineers.

Performance evaluation and a sizing method for hydrodynamic separators treating urban stormwater runoff

2014 ◽  
Vol 69 (10) ◽  
pp. 2122-2131 ◽  
Author(s):  
D. H. Lee ◽  
K. S. Min ◽  
J.-H. Kang
Keyword(s):  
Particle Size ◽  
Removal Efficiency ◽  
Performance Monitoring ◽  
Particle Diameter ◽  
Storm Event ◽  
Weibull Function ◽  
Storm Events ◽  
Mean Values ◽  
Median Particle ◽  
Urban Catchments

This study reports on 6 years of performance monitoring of stormwater hydrodynamic separators in Korean urban catchments. One hundred and thirty-seven storm events were monitored in four hydrodynamic separators of two different types from 2006 to 2012. Mean values of the event average removal efficiencies of total suspended solids (TSS) for the four hydrodynamic separators were 43.69, 8.54, 42.84, and 14.35% with corresponding mean values of the event average surface overflow rates of 28.62, 40.07, 16.02, and 38.81 m/h, respectively. The low TSS removal efficiency was due to the high instantaneous surface overflow rates frequently occurring throughout a storm event and the abundance of fine particle fractions in the inflow (median particle diameter &lt;75 μm). The Weibull function was used to simulate particle size distribution (PSD) in the runoff and the simulated PSD functions were further applied to the discrete settling theory to develop curves of TSS removal efficiency, as a function of surface overflow rate and median particle size of the inflow. The developed curves should be useful in determining the design peak flow rate and the size of a hydrodynamic separator for a stated goal of TSS removal efficiency.

Effect of Reaction Temperature in the Alumina Preparation by Combustion in a Muffle Furnace

2014 ◽  
Vol 775-776 ◽  
pp. 687-691 ◽  
Author(s):  
Mirele Costa da Silva ◽  
Ana Cristina F. Melo Costa ◽  
Hélio Lucena Lira ◽  
Normanda Lino de Freitas
Keyword(s):  
Size Distribution ◽  
Particle Diameter ◽  
Synthesis Temperature ◽  
Effect Of Temperature ◽  
X Ray Diffraction ◽  
Muffle Furnace ◽  
X Ray ◽  
Median Particle Diameter ◽  
Particles Size Distribution ◽  
Median Particle

The aim of this study is to evaluate the effect of temperature during the synthesis of alumina by combustion in a muffle furnace. The alumina was characterized by X-ray diffraction, particles size distribution and scanning electron microscopy. The results showed that the synthesis temperature of the alumina can affect the structure of the produced samples. The size distribution of the median particle diameter reached higher value for the alumina synthesized at 500°C with 16.07 μm, the range of the total distribution of particles is introduced to the large alumina synthesized 500 and 600°C and close synthesized when 700 and 800°C. The phase of the alumina was identified only after the synthesized sample at 800°C with crystallite size of 22.16 and 6.75 μm synthesized samples 800 and 900°C, respectively. With respect to morphology, increased synthesis temperature was not enough to significantly change.

Development of Conductive and Anticorrosive Paint Dispersed with Carbon Particles for Metal Separators of PEFC

2007 ◽  
Vol 534-536 ◽  
pp. 1433-1436
Author(s):  
Masahiro Okahara ◽  
Zenzo Ishijima ◽  
Minoru Shirahige
Keyword(s):  
Electricity Generation ◽  
Particle Diameter ◽  
Conductive Filler ◽  
Polymer Electrolyte Fuel Cells ◽  
Passive State ◽  
Severe Reaction ◽  
Mixed Powder ◽  
Carbon Particles ◽  
Median Particle Diameter ◽  
Median Particle

A resin paint dispersed with carbon particles was developed for the purpose of good conductivity and corrosion resistance for metal separators used in Polymer Electrolyte Fuel Cells (PEFC). The use of metal separators, especially Ti separators is a technology which has received much attention for its practical application as it allows for much greater compact stacking, since it is superior in both productivity and strength, in comparison with that of carbon molding separators. However, if pure Ti separators are used in a severe reaction of electricity generation, there is a deterioration in conductivity, because of the formation of a passive film, which subsequently causes electricity generation difficulties after a few hours of use. Through examining the type of resin used for the purpose of controlling the passive state, the grain size of the conductive filler (graphite (Gr) + carbon black (CB)) and the composition combination for the purpose of secure conductivity, it was found that the combination of a scaly graphite-furnaced black mixed powder with a median particle diameter of 4μm and VDF-10%HFP copolymer resin was optimal. As a result of performing a single cell electricity generation evaluation of the Ti separator, which had the above mentioned coating material, the life of 22,000 or more hours was confirmed and an electricity generation evaluation is now being undertaken.

scholarly journals Investigation of a Ventilation System for Energy Efficiency and Indoor Environmental Quality in a Renovated Historical Building: A Case Study

2019 ◽  
Vol 16 (21) ◽  
pp. 4133 ◽  
Author(s):  
Richard Nagy ◽  
Ľudmila Mečiarová ◽  
Silvia Vilčeková ◽  
Eva Krídlová Burdová ◽  
Danica Košičanová
Keyword(s):  
Energy Consumption ◽  
Relative Humidity ◽  
Environmental Quality ◽  
Natural Ventilation ◽  
Ventilation System ◽  
Sick Building Syndrome ◽  
Co2 Concentration ◽  
Indoor Environmental Quality ◽  
Historical Building ◽  
The Mean

This paper emphasizes the importance of environmental protection regarding the reduction of energy consumption while maintaining living standards. The aim of the research is to observe the effects of mechanical and natural ventilation on energy consumption and building operation as well as indoor environmental quality (IEQ). The results of indoor environmental quality testing show that the mean relative humidity (31%) is in the permissible range (30%–70%); the mean CO2 concentration (1050.5 ppm) is above the recommended value of 1000 ppm according to Pettenkofer; and the mean PM10 concentration (43.5 µg/m3) is under the limit value of 50 µg/m3. A very large positive correlation is found between relative humidity and concentration of CO2 as well as between the concentration of PM5 and the concentration of CO2. The most commonly occurring sick building syndrome (SBS) symptoms are found to be fatigue and the feeling of a heavy head.

scholarly journals Using OCO-2 Satellite Data for Investigating the Variability of Atmospheric CO2 Concentration in Relationship with Precipitation, Relative Humidity, and Vegetation over Oman

Water ◽  
2019 ◽  
Vol 12 (1) ◽  
pp. 101
Author(s):  
Foroogh Golkar ◽  
Malik Al-Wardy ◽  
Seyedeh Fatemeh Saffari ◽  
Kathiya Al-Aufi ◽  
Ghazi Al-Rawas
Keyword(s):  
Time Series ◽  
Relative Humidity ◽  
Vegetation Index ◽  
Normalized Difference Vegetation Index ◽  
Co2 Concentration ◽  
Atmospheric Co2 ◽  
Monsoon Region ◽  
Annual Cycles ◽  
Atmospheric Co2 Concentration ◽  
Carbon Dioxide Co2

Recognition of the carbon dioxide (CO2) concentration variations over time is critical for tracing the future changes in climate both globally and regionally. In this study, a time series analysis of atmospheric CO2 concentration and its relationship with precipitation, relative humidity (RH), and vegetation is investigated over Oman. The daily XCO2 data from OCO-2 satellite was obtained from September 2014 to March 2019. The daily RH and precipitation data were also collected from the ground weather stations, and the Normalized Difference Vegetation Index was obtained from MODIS. Oman was studied in four distinct regions where the main emphasis was on the Monsoon Region in the far south. The CO2 concentration time series indicated a significant upward trend over different regions for the study period, with annual cycles being the same for all regions except the Monsoon Region. This is indicative of RH, precipitation, and consequently vegetation cover impact on atmospheric CO2 concentration, resulting in an overall lower annual growth in the Monsoon Region. Simple and multiple correlation analyses of CO2 concentration with mentioned parameters were performed in zero to three-month lags over Oman. They showed high correlations mainly during the rainfall period in the Monsoon Region.

Sign in / Sign up

Export Citation Format

Share Document