Sharif Digital Repository

Missing or incomplete data in short or long intervals is a common problem in measuring air pollution. Severe issues may arise when dealing with missing data for time-series prediction schemes or mean analysis. This study aimed to develop a new regression imputation framework to impute missing values in the hourly air quality data set of Tehran and enhance the applicability of Tehran Air Pollution Forecasting System (TAPFS). The proposed framework was designed based on three types of features including measurements of other stations, WRF and CAMx physical models. In this framework, elastic net and neuro-fuzzy networks were efficiently combined in a two-layer structure. The framework was... 

Currently PM2.5 is a major air pollution concern in Tehran, Iran due to frequent high levels and possible adverse impacts. In this study, which is the first of its kind to take place in Tehran, composition and sources of PM2.5 and carbonaceous aerosol were determined, and their seasonal trends were studied. In this regard, fine PM samples were collected every six days at a residential station for one year and the chemical constituents including organic marker species, metals, and ions were analyzed by chemical analysis. The source apportionment was performed using organic molecular marker-based CMB receptor modeling. Carbonaceous compounds were the major contributors to fine particulate mass... 

Reformer gas (syngas) addition to main fuel is a practical solution for combustion timing control in HCCI engines. This study emphasizes the understanding of various effects of reformer gas (RG) addition, with composition of 75%vol H2 and 25%vol CO, in HCCI combustion by developing an artificial inert species method and using a detailed chemical kinetics multi-zone model. Three fuels (iso-octane, n-heptane, and natural gas) with different autoignition characteristics were used in this study. The developed multi-zone model was validated for mentioned fuels at various percentages of RG using six experimental cases of a single-cylinder CFR engine. The results showed that increasing reformer gas... 

Reactivity Controlled Compression Ignition can be extended over a wide spectrum of fuels and is anticipated as a promising strategy in meeting current and future emission regulations. In this study, the effect of n-butanol addition on combustion characteristics and emissions in a reactivity controlled engine was investigated experimentally. Different ratios of butanol-diesel blends at different settings of EGR and premixed ratios were applied to a light duty diesel engine. The butanol-diesel blends were directly injected into the combustion chamber while gasoline was injected at the intake port. Combustion phasing was maintained at 2.7 °CA for all of test points by adjusting fuel injection... 

Fine particulate matter characterized as PM2.5 is the most important criteria air pollutant in the city of Tehran. Tehran is one of the most polluted cities of the Middle East based on annual mean PM2.5 concentrations. Tehran emission inventory shows the large contribution of mobile sources to the total particles. PM2.5 source apportionment studies show large fraction of black carbon (BC) in the total mass of PM2.5, especially during the cold seasons. BC is the product of incomplete combustion that is mainly derived from diesel engines and rich-burned gasoline carburetor engines on scooters and light-duty vehicles. The present study shows the results of a large experimental campaign in which... 

There is limited evidence for short-term association between mortality and ambient air pollution in the Middle East and no study has evaluated exposure windows of about a month prior to death. We investigated all-cause non-accidental daily mortality and its association with fine particulate matter (PM2.5), nitrogen dioxide (NO2), and the Air Quality Index (AQI) from March 2011 through March 2014 in the megacity of Tehran, Iran. Generalized additive quasi-Poisson models were used within a distributed lag linear modeling framework to estimate the cumulative effects of PM2.5, NO2, and the AQI up to a lag of 45 days. We further conducted multi-pollutant models and also stratified the analyses by... 

In recent years, the city of Tehran has frequently experienced severe air pollution episodes, and the increase in the use of vehicles has exacerbated this critical situation. It is unclear to what extent each vehicle category contributes to the production of pollution during a pollution event. For this purpose, a combination of the weather research and forecasting (WRF) and the Comprehensive Air Quality Model with Extensions (CAMx) modeling systems was used to simulate the distributions of pollutant concentrations over Tehran in a pollution episode from December 3 to 23, 2017. First, the performance of the modeling system was evaluated with respect to the simulation outputs against... 

The city of Tehran, the capital of Iran, has been facing severe air quality problems. The air quality of Tehran has been stated as unhealthy over one-third of year during the last two decades. According to the last emission inventory of Tehran for the base year of 2013 mobile sources contribute by about 6, 46, 98, 87, and 70% of total primary SOx, NOx, CO, VOC and PM emission. A number of policies have been implemented in Tehran during the last two decades to tackle the air quality issue. Concentrated mostly on transportation sector, these policies aimed to improve fuel quality and emission performance of vehicles. Nevertheless, there is no quantified evaluation regarding the effectiveness... 

Oral administration is a pillar of the pharmaceutical industry and yet it remains challenging to administer hydrophilic therapeutics by the oral route. Smart and controlled oral drug delivery could bypass the physiological barriers that limit the oral delivery of these therapeutics. Micro- and nanoscale technologies, with an unprecedented ability to create, control, and measure micro- or nanoenvironments, have found tremendous applications in biology and medicine. In particular, significant advances have been made in using these technologies for oral drug delivery. In this review, we briefly describe biological barriers to oral drug delivery and micro and nanoscale fabrication technologies.... 

Cell survival during the early stages of transplantation and before new blood vessels formation is a major challenge in translational applications of 3D bioprinted tissues. Supplementing oxygen (O2) to transplanted cells via an O2 generating source such as calcium peroxide (CPO) is an attractive approach to ensure cell viability. Calcium peroxide also produces calcium hydroxide that reduces the viscosity of bioinks, which is a limiting factor for bioprinting. Therefore, adapting this solution into 3D bioprinting is of significant importance. In this study, a gelatin methacryloyl (GelMA) bioink that is optimized in terms of pH and viscosity is developed. The improved rheological properties... 

With over 8 million inhabitants and 4 million motor vehicles on the streets, Tehran is one of the most crowded and polluted cities in the Middle East. Frequent exceedances of national daily PM2.5 limit have been reported in this city during the last decade, yet, the chemical composition and sources of fine particles are poorly determined. In the present study, 24-hour PM2.5 samples were collected at two urban sites during two separate campaigns, a one-year period from 2014 to 2015 and another three-month period at the beginning of 2017. Concentrations of organic carbon (OC), elemental carbon (EC), inorganic ions, trace metals and specific organic molecular markers were measured by chemical... 

Low temperature combustion potentially can improve engine efficiency coupled with the benefits of low nitrogen oxides, and particulate matter emissions, and vice versa high unburned hydrocarbon and carbon oxide emissions through in-cylinder fuel reactions. In this survey, the experiments were carried out using a modified one-cylinder reactivity controlled compression ignition engine, dual-fueled diesel/compressed natural gas and biodiesel/CNG, to investigate the effects of direct injection strategies on the engine combustion efficiency and emission characteristics. Different ratios of biodiesel blends at different premixed ratios were applied to the dual-fuel engine. The results showed that... 

This study uses a 5-lobe symmetric model to investigate total, lobar and generational particle deposition fractions in the lungs during successive cycles. It was found that for the particle size between 0.05 and 2 μm and the tidal volumes greater than 1000 ml, the effect of successive cycles helped predict more deposition fraction per cycle up to about 16% than that of a single cycle. The mentioned range of tidal volumes corresponds to light or heavy physical activities. Therefore, it can be understood that people, when physically active, exposed to particulate matter within the mentioned size range are at higher health risk as compared to both the resting state and the same state... 

Tehran, the capital of Iran, is one of the most polluted cities in the Middle East. However, there is no clear evidence of the effects of Tehran green spaces on reducing air pollution because there are still challenges to application of vegetation for improving air quality. The current study investigates the effects of a large volume of green space with 275 ha area in the vicinity of major highways on nearby air quality. Similar environments are often seen in many cities around the world. A computational fluid dynamics model containing aerodynamics and deposition effects of vegetation was used to simulate pollutant dispersion for eight wind directions and three different foliage densities.... 

Coupled weather forecasting and chemical transport models are useful tools to evaluate air pollution episodes in big cities for the purpose of forecasting and air pollution abatement measures' evaluation. However, large set of accurate data of various sources and modeling calibrations are needed for such complex modeling system to be reliable. The problem becomes more obvious when the model is operated over a domain in which there is a general lack of accurate input data such as emission inventory data. The current study investigates the possibility of model tuning for more accurate prediction of air pollutant concentrations in the city of Tehran in an air pollution episode as a case study.... 

An assessment of trends in main air pollutant concentrations (including CO, SO2, NO2, O3, PM2.5, and Asbestos) is conducted for the years 2005–2016 for the city of Tehran, Iran. The focus has been on the contribution of anthropogenic emissions to the observed trend, particularly the role of related mitigation plans implemented in the period of interest. A significant decreasing trend (about 50%) was observed in CO and SO2 concentrations during the considered time interval, which was explained by improvement plans in fuel quality and vehicle emission standards. While a substantial elevation (more than 50%) in NO2 levels was detected over the study period, variant trends were observed during... 

Each year, considerable levels of dust particles coming from arid regions of the earth contribute to the atmosphere. Because dust has serious environmental and human health effects, predictions of dust concentrations and their contribution to PM surface concentrations are essential for atmospheric research and the implementation of air quality programs and rules. This study aims to assess dust contributions to PM2.5 in Tehran in order to provide guidance for air quality management systems as well as validate the updated Dust Regional Atmospheric Model version 2 (BSC-DREAM8b) and the NMMB/BSC-Dust model using chemical speciation of ground-based measurements of PM2.5. Accurate and reliable... 

The current study was designed to assess the association between temporal variations in urban PM2.5 chemical composition, sources, and the oxidative stress and inflammatory response in an alveolar macrophage (AM) model. A year-long sampling campaign collected PM2.5 samples at the Sharif University in Tehran, Iran. PM-induced reactive oxygen species (ROS) production was measured both with an acellular dithiothreitol consumption assay (DTT-ROS; ranged from 2.1 to 9.3 nmoles min−1 m−3) and an in vitro macrophage-mediated ROS production assay (AM-ROS; ranged from 125 to 1213 μg Zymosan equivalents m−3). The production of tumor necrosis factor alpha (TNF-α; ranged from ~60 to 518 pg TNF-α m−3)... 

This study investigates the secondary organic aerosol (SOA) formation potential of carburetor motorcycles exhaust. This type of two-wheeler is a popular means of transport in many Asian cities. A volatility-based numerical model was employed to predict SOA formation from a fleet of motorcycles in Tehran, capital of Iran. The fleet was a combination of four-stroke, gasoline-powered motorcycles with different engine displacement volumes. Total hydrocarbon (THC) emission factors of all motorcycles were previously measured in a chassis dynamometer laboratory according to cold start Euro-3 emissions certification test procedures. Due to incomplete combustion and lack of control on exhaust... 

Predicting the way diseases spread in different societies has been thus far documented as one of the most important tools for control strategies and policy-making during a pandemic. This study is to propose a network autoregressive (NAR) model to forecast the number of total currently infected cases with coronavirus disease 2019 (COVID-19) in Iran until the end of December 2021 in view of the disease interactions within the neighboring countries in the region. For this purpose, the COVID-19 data were initially collected for seven regional nations, including Iran, Turkey, Iraq, Azerbaijan, Armenia, Afghanistan, and Pakistan. Thenceforth, a network was established over these countries, and the...