Sharif Digital Repository

This study has been carried out for investigating the need for an appropriate and fast seismic analysis method to be applied in performance based design (PBD), and show the application of Endurance Time (ET) method and it’s advantages in PBD. Necessary theories were generated in hazard analysis, bi-directional seismic analysis, introduction of dynamic push-over curve and application. As a secondary goal, potential of this method in more complicated nonlinear domains is assessed. Application of ET and its advantages in PBD is shown with an example of SMF, NDCBF, CBF and BRBF building after modeling nonlinear interactional behavior of beams and columns, and also modeling buckling and... 

The problem of PM pollutants has become one of the main environmental concerns of Tehran city due to the growth of city population and industrialization. As a consequence of this problem there is an increasing trend in the number of unhealthy days in Tehran in terms of air quality in recent years. Solving this problem needs strict regulations to limit the amount of pollutants released from vehicles, industries and power plants. To help this cause, this study investigates the effect of emissions and climate change under RCP scenarios on future PM2.5 concentration in Tehran by using WRF-SMOKE-CMAQ modeling system. The result of simulation of climate conditions under RCP8.5 scenario in 2050... 

Enzymes are biological catalysts that reduce the activation energy of a reaction in a short time and thus increase the speed of the reaction. The most common enzymes used in various industries, including the detergent industry, are lipases, amylases, celluloses, and proteases. Proteases are one of the most important industrial enzymes. The performance of enzymes is affected by the durability of their activity in long-term storage. Therefore, using a technique that can maintain the activity of enzymes, under storage and usage conditions, is an essential step in making a product containing enzymes. Stabilization-immobilization operation is one of the important downstream processes in... 

This study presents the advantages of using unsymmetrical buckling restrained braces in zipper frames for simultaneous improvement of peak and residual response of low- and mid-rise buildings. It is demonstrated that such combination allows for the usage of benefits of each of these systems, namely the significant energy dissipation capacity of buckling restrained braces and better distribution of hysteretic energy dissipation demands through the elevation observed in zipper frames. It has already been shown that using buckling restrained braces of varying yield strengths within each story of a building can improve the residual response of buckling-restrained-braced frames without severely... 

Hydrologic analysis in order to design the collection and transmission structures of urban runoff require some time parameters as input that the accuracy of these analysis is directly sensitive to the accuracy of these parameters. Among these parameters, the time of concentration is the most frequently utilized time parameter and numerous equations for estimating the time of concentration in urban watersheds have been proposed. The purpose of this study is to propose some equations to estimate the time of concentration of overland flow in small urban watersheds with pattern similar to arid and semiarid regions and investigate the effect of using LIDs on reducing the surface runoff.... 

Recent earthquakes indicate the importance of retrofitting existing structures to achieve an acceptable level of performance. Use of bracing systems is a cost-effective method for seismic retrofitting of existing steel frames. In particular, Buckling Restrained Braces (BRBs) and Special Concentrically Bracing systems (SCB) are practical choices to be used because of their large energy dissipation capacity especially under moderate to severe earthquakes. Buckling restrained braces which yield in both tension and compression, exhibits stable and predictable hysteretic behavior. In this study several existing steel frames, which are designed based on older versions of the building codes, have... 

In this paper the predictive equations for collapse assessment of shear links used in eccentric braced frames are developed. An extensive database including results of over 70 cyclic tests on steel wide flange shear links is collected and the structural parameters governing the hysteresis behavior are calibrated using a simplified numerical model. The methodology of calibration is to minimize the discrepancy between the experimental hysteresis loops and the corresponding numerical results using Particle Swarm Optimization (PSO) algorithm. The objective function of PSO algorithm is minimized by iterating parameters that govern the hysteresis behavior of the numerical model. Stepwise... 

Focus of the present research is on the study and cognition of sources of carbonaceous compounds present in PM2.5, particularly secondary organic carbon. For this purpose, two different approaches were used. The first approach investigates the SOA formation from internal combustion engines exhaust and unburned fuel (bottom-up approach). The second approach studies the contribution of each of the primary and secondary sources to PM2.5 mass, whereby secondary organic carbon share is obtained (top-down approach). Modeling SOA formation from vehicles exhaust showed that diesel vehicles have greater SOA formation potential than gasoline vehicles, due to large amount of S/IVOCs present in their... 

Laboratory studies to investigate the effects of different saline concentrations (such as sodium chloride or calcium chloride) on the soil water retention behavior of clayey soils and their volumetric changes have received much attention recently. However, many previous studies have investigated these effects in only one path of the SWRC (wetting or drying path) and the effects of saline concentration on hydraulic hysteresis have not been considered. In addition, researchers have frequently studied these effects on SWRC on clay samples, and little research has been done on collapsible soils. Therefore, the most important purpose of this study is to investigate the effects of increasing... 

The role of a mathematical model is to explain a set of experiments, and to make predictions. In setting up a mathematical model of a biological process, by a set of differential equations, it is very important to determine the numerical value of the parameters. For biological processes are typically valid only within a limited range of parameters. In the last decades, various cancer models have been developed in which the evolution of the densities of cells (abnormal, normal, or dead) and the concentrations of biochemical species are described in terms of differential equations. Some of these models use only ordinary differential equations (ODEs), ignoring the spatial effects of tumor... 

Considering high potential of solar energy and exhaustibility of fossil fuels in Iran, using solar energy seems to be inevitable. But one of the main problems in the application of these systems is high investment and maintenance costs. So, in this thesis, suitable solution is presented for decreasing cost and optimizing of a solar absorption refrigerator based on developed energy model. This system consists of two CPC solar collectors and a thermal energy storage system using phase change materials that provides input energy to the generator of absorption refrigerator. The exergy efficiency of system components is calculated by relations of energy model and exergy analysis. Then... 

Physicians use charts that are prepared by experiments on animals or humans to prescribe drug dosage for patients. This method requires much more time by the Ministry of Health to approve new drugs to be used in health-care centers. Furthermore،we have no sight on how a specific drug is going to be diffuse in our body. In order to predict the distribution of a drug or any minerals in the kidney we need to model it. The first step would be modeling the important species that influence the urine concentrating mechanism. Due to the complications in modeling that mechanism especially in the inner medulla zone، we hadn’t solid information regarding that area. It is about half a century that... 

In recent years, in Tehran, air pollution became one of the major problems in this city. Among air pollutants, particle matter (PM) is very important in aspect of negative effect on environment and human health. Effective control of these particles requires correct determination of rules and adopting appropriate managing policy which are mostly very cost-consuming. Rules determination and adopting appropriate policy is very challenging in Tehran due to lack of sufficient information about concentration dispersion of such particles. The aim of this study is to recognize the factors of producing PM10 and appropriate understanding of changes of particle matter concentration of Tehran by... 

Direct steam generation (DSG) process using linear FRESNEL collectors has been developed widely in recent years and is one of the most promising solar technologies for thermal power generation, Industrial processes and domestic usage. In this process water as heat transfer fluid (HTF) is heated through a solar field. Continuous breakthroughs are being achieved on improvement of these collectors. A multi-phase CFD model is developed to calculate the wall temperature of linear Fresnel absorber tubes and fluid properties including temperature, velocity, and pressure. In order to design the collector field and identify the critical condition such as overheating of the absorber tubes, modeling of... 

These days, according to increasing requirement to the applications of clean rooms in industries in and within the developing industry of computer, positive indicators that show a real need to a compere comprehensive study and research about the Clean rooms, in oder to predict the distribution and dispersal of the particles. Correct determination of indoor airflow and particle concentration distribution results in new standard development for Clean rooms. As computational fluid dynamics has become a powerful tool for indoor airflow studies, in this research, influence of effective parameters on the flow and concentration distribution in clean rooms has been... 

Concrete-filled FRP tubes have gained popularity among structures in areas with harsh environmental condition. Despite their unique material properties such as resistance to corrosion, noticeable axial stiffness, and durability, FRP materials have poor resistance to elevated temperatures. This paper presents numerical investigations on the behavior and capacity of concrete-filled pultruded GFRP tubes (CFGFTs) after exposure to elevated temperatures under concentric compression. Variables in this study were the tube’s thickness of 3, 5, and 7mm, the infill concrete’s compressive strengths of 30 and 60MPa, and the exposure temperature of 25, 100, 200, 300, and 400°C. The results in this study... 

The urine formation and excretion system has long been of interest for mathematicians and physiologists to elucidate the obscurities within the process happen in renal tissue. In this study, a novel and absolutely three-dimensional approach is utilized for modeling urine concentrating mechanism in rat renal outer medulla which is essentially focused on demonstrating the significance of tubule's architecture revealed in anatomic studies and physiological literature. Since nephrons and vasculatures work interdependently through a highly structured arrangement in outer medulla which is dominated by vascular bundles, a highly detailed functional unit is proposed and also it is strongly justified... 

Resolvers, due to their robust structure, are widely used in automation systems. Among the types of resolvers, the accuracy of the Wound Rotor (WR) resolver in the occurrence of common mechanical errors is higher than other types of resolvers. therefore, in this thesis, an AFWRR is studied to improve the performance. Increasing the number of poles in WR resolvers is a good solution for increasing the accuracy of these electromagnetic position sensors. However, high-speed WR resolvers due to employing fractional slot windings suffer from rich sub-harmonics in the induced voltages. A common solution for suppressing the undesirable sub-harmonics is using multi-layer winding with appropriate... 

Poor hole cleaning while drilling due to problems such as pipe sticking and ROP reducing will increase drilling cost. It is almost impossible to optimize the hole cleaning during the well planning due to the large number of effective parameters, so it is very important to monitor the hole cleaning conditions while drilling. The best way to monitor the well condition during drilling is using the real time drilling data (RTDD). Hook load (HKL) is one of many RTDD parameters that measured at the surface during drilling operations so it can be used to evaluate the hole cleaning condition. In this research, how to process the raw data recorded while drilling has been investigated. In the next... 

Concentration brings a twofold result to the market. From one side, it reduces the competition and then the number of varieties in the market, which discourages consumption; from another side, however, it reduces the price of goods due to increasing returns to scale and so encourages consumption. This controversial role of concentration raises the question that which degree of concentration might be, say, optimum for the market. Based on the Krugman approach, this study makes a relation between the number of firms, export volume, marginal and average fixed cost of production. We show that when number of firms reduces in the market, export volume could increase because of a reduction in...