Sharif Digital Repository

The origins and evolution of the Middle Eastern dust storms which frequently impact the residents of this arid region were studied. A methodology was adapted and developed to identify the desert regions of potential dust sources and determine their contributions to PM10 concentrations in the highly-populated receptor city of Tehran, Iran. Initially, the episodes of regional dust intrusion and the resulting amounts of increase in the particulate concentrations during these episodes were determined using a statistical analyzing methodology. The dust episodes were also inspected with the aerosol index information from the Ozone Monitoring Instrument (OMI). The Hybrid Single-Particle Lagrangian... 

Because of the recent frequent observations of major dust storms in southwestern cities in Iran such as Ahvaz, and the importance of the ionic composition of particulate matters regarding their health effects, source apportionment, etc., the present work was conducted aiming at characterizing the ionic composition of total suspended particles (TSP) and particles on the order of ∼10 μm or less (PM10) during dust storms in Ahvaz in April-September 2010. TSP and PM10 samples were collected and their ionic compositions were determined using an ion chromatography. Mean concentrations of TSP and PM10 were 1,481.5 and 1,072.9 μg/m 3, respectively. Particle concentrations during the Middle Eastern... 

Signal processing in noise radar is always done by calculating the cross-correlation between transmitted and received signals. Strong echoes of near targets present relatively high sidelobes in the correlation output, so they can conceal weak echoes of weak targets (masking effect). Many classical and modern methods for alleviating this effect have been offered, however, most of them are based on signal processing in the receiver side. In this paper, a new method of waveform design, able to decrease masking effect, is presented. Contrary to the other methods, this method keeps the matched filter structure in receiver unchanged and does not need performing any extra process in the receiver... 

Since space diversity and frequency diversity are both efficient techniques in the radar applications, we propose in this paper a method for simultaneous usage of both techniques. On this basis, a multi-frequency array radar in which all frequencies are used simultaneously to increase the number of targets that can be uniquely identified, is introduced and analyzed. First, the signal model for such a system is derived and then, it is shown how the use of multi-frequency signal can noticeably improve the parameter identifiability. Specifically, we show the maximum number of targets that can be uniquely identified by the multi-frequency array radar is L times that of its single-frequency array... 

Using the newly developed Middle East Dust Index (MEDI) applied to MODIS satellite data, we consider a relationship between the recent desertified regions, over the past three decades, and the dust source points identified during the period of 2001-2012. Results indicate that major source points are located in Iraq and Syria, and by implementing the spectral mixture analysis on the Landsat TM images (1984 and 2012), a novel desertification map was extracted. Results of this study indicate for the first time that c.a., 39% of all detected source points are located in this newly anthropogenically desertified area. Using extracted indices for Deep Blue algorithm, dust sources were classified... 

Analysis and identification of vortex structures and their formation, particularly in swirl flows, have received widespread interest among researchers in the field of fluid mechanics. Due to the importance of vortex structures and their applications in combustion chambers, a special type of combustion chamber, which is called a “bidirectional swirl combustor,” has been investigated in this work. The dependence of vortex structures on the combustion chamber geometry and fuel injection location in cold flow, the effect of hot flow on coherent structures, and the difference between vortex structures in hot and cold flows have been studied as well. A common characteristic which is in combustion... 

In this article, the relation between meteorological parameters and dust activities in western Iran has been studied. Satellite-based data achieved from TOMS are used to investigate the dust activities within a time period of 30 years. In the first part of this study, we examine the statistical trend of Aerosol Index (AI) and local meteorological parameters in 15 different stations. The same patterns of AI variations in all stations indicate that this region has always been subjected to dust storms which originate from similar sources in the neighboring countries that could be known as a sole dust transfer system. In the second part, we investigate the spatial correlation between the... 

The construction of permeable pavement (PP) in sidewalks of urban areas is an alternative low impact development (LID) to control stormwater runoff volume and consequently decrease the discharge of pollutants in receiving water bodies. In this paper, some laboratory experiments were performed to evaluate the efficiency of a PP subjected to sediment loadings during its life span. Simple infiltration models were validated by the laboratory experiments to evaluate the trend and extend of PP infiltration capacity throughout the life of the pavement operation. In addition, performances of the PP in removing total suspended solids (TSS) and selective nutrient pollutants such as NO3 −, NH4 + and...