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Estimating the size of shadow economy is of special importance in setting macroeconomic variables and fiscal policies. In recent years, the fuzzy inference sets have been used for measuring shadow economy. In this paper, we present eight new fuzzy indicators for modeling and estimating the size of shadow economy. Thus, according to Lucas definition, we divide the shadow economy into four sectors and define two indicators for each sector. After three fuzzy inference phases, we measure the size of shadow economy. Our results indicate that the effect of production household on Iran’s shadow economy size is decreasing; and irregular, informal and illegal sectors impact size of shadow economy. In addition, the size of Iran’s shadow economy is estimated around 13 percent of GDP, on average, over 1970- 2007.  

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The use of recycled materials in Portland cement concrete (PCC) has become more and more popular in recent years. Most recycled materials applied in PCC are used to replace coarse aggregates, fine aggregate, or act as cementitious additives. When using recycled materials in PCC, it is desirable that the properties of the concrete can also be improved. Plain PCC, while typically having high strength, generally possesses very low post failure toughness, which may cause abrupt failure of structures and short pavement life. Reclaimed or recycled asphalt pavements (RAP) have been routinely used in the construction of pavement granular bases and hot-mix asphalt concrete. RAP is the removed and/or processed asphalt pavement materials containing both aged asphalt and aggregates. The asphalt coated on the surface of the aggregates typically forms a film with a thickness between six to nine microns. The use of RAP in PCC, though seems to be a viable solution to improve the toughness, has received little attention by research communities. Cementitious systems incorporating polymers have received considerable inter- national attention, especially over the last 30 years or so. The reason for this interest can be attributed to the improved engineering properties when compared to the unmodified materials, e.g. tensile/flexural strength, toughness and durability, the latter including resistance to carbonation, chloride penetration, and frost damage. Additionally, these systems may be used as repair materials where a good bond with the existing concrete or steel is required. Many polymer concrete combinations are available. Polymer-modified cement mortar and concrete (PMC): polymer particles in the form of a latex or redispersible powder are added to a fresh cementitious mix which is then cured. The most commonly used latexes are aqueous suspensions of styrene- butadiene-rubber (SBR) and various acrylics (Ac) containing 45±50% polymer solids. In SBR, the ratio of styrene to butadiene governs the properties of the polymer, with 60±65% styrene giving a good balance. Higher styrene contents would improve compressive and tensile strengths but reduce adhesion and raise the minimum film-forming temperature (MFT). In this study, the effect of SBR latex and silica fume on the mechanical strength (compressive, bending, and splitting tensile strength, elasticity modulus, toughness index), permeability (water penetration, rapid chloride penetration (RCPT), electrical specific resistivity) and microstructure of concrete made with recycled asphaltic aggregates to replaced with natural coarse aggregate (33%, 66% and 100% by weight) were studied. Results showed that the adding of latex and silica fume significantly increased mechanical strength and decrease permeability of concrete mixes. quality and microstructure of interfacial transition zone (ITZ) between aggregate- cementitious matrix by use of scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy analysis (EDX) was evaluated. SEM images showed that the mixtures containing latex and silica fume had uniform and smooth structure at surface aggregate- cementitious matrix, and also EDX analysis represents reducing the thickness of ITZ and the calcium to silicon ratio. For assessment of latex effect mechanism on compressive strength, three different type of curing on cube mixtures were applied. The results showed that compressive strength of specimens cured at temperatures significantly increased, which indicates of heating- help to formation polymeric membrane in specimens containing latex.

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Various studies on cars aerodynamics focusing on the Ahmed body model as a standard and simplified shape of a road vehicle have been carried out in recent years. In this paper plasma actuator as an active flow control method has been employed to control flow around the rear part of an Ahmed body with the rear slant angle of 25°. Experiments performed in a wind tunnel in free stream velocity of U=10m/s using steady and unsteady plasma actuator excitations. Pressure distribution on the rear part was measured by 52 sensors, and also total drag force was extracted by a load cell. More over smoke flow visualization was carried out to determine the flow pattern around the body. The results showed that employing plasma actuator not only has an effective influence on pressure distribution on the rear slant surface, but also reduces total drag force in steady and unsteady excitations 7.3% and 5%, respectively. As a result, based on flow visualization and pressure distribution tests, plasma actuator in steady state actuation, could distract D-shape vortices and suppress the separated flow over the rear slant.