Sharif Digital Repository

During preliminary investigation phase of the national Chabahar-Zahedan railway line, serious geotechnical problems including non-uniform settlements, tensile cracks, and local collapse were reported in parts of the path near the coastline. A follow-up field investigation revealed that the in-situ soil at construction site has a metastable structure being sensitive to saturation and loading. Therefore, a comprehensive series of physical, chemical, electro-chemical, and geotechnical tests were conducted to classify and characterize the soil properties and behavior in its natural state. The natural soil was classified as a clayey loess with moderately dispersive to dispersive characteristics.... 

In this paper a simplified object specific ray tracing method is proposed to solve the important propagation problem of scattering by the lamp-posts. In fact, radiation from the transmitter antenna is modeled with a two ray incidence model and unknown currents on lamp-posts are computed using the Multi-Level Fast Multi-pole Method (MLFMM) which is an extension of the MoM (Method of Moments). In addition, scattering by lamp-posts is computed using the superposition of current elements electric fields based on the discrete complex image method (DCIM) in presence of a real ground with complex relative permittivity. The scattered near fields are considered instead of far fields. Based on this... 

Ground improvement techniques are inevitable for weak soils that cannot endure the design load imposed by superstructures. Deep mixing technique (DMT) as one of these methods is promising and effective when a deep soil layer with low bearing capacity is encountered. Such deposits are quite common in the South-west of Iran where the studied site is located. In order to validate the influence of DMT on the enhancement of strength, both in-situ and laboratory tests were conducted. Afterwards, a parametric study was carried out to investigate the influence of key factors including cement content, water–cement ratio, curing time and plasticity index (PI) on the performance of DMT. In summary, a... 

There are a number of studies on seismic performance of a diagrid structure indicating that it is an effective choice for constructing tall buildings. This research investigates the seismic behavior of diagrid structures and quantifies its seismic performance factors including the response modification coefficient (R-factor), the over-strength factor (Ω0) and the displacement amplification factor (Cd) based on the FEMA P695 methodology. In that regard, a group of 3-D steel diagrid archetype models with different number of floors and various diagonal angles are designed using different R-factors. Then, in the first step, the over-strength factors of these models are determined by performing... 

The seismic performance of diagrids equipped with buckling restrained braces (BRBs) is investigated. In that regard, the effects of BRBs on the seismic performance characteristics of diagrids such as response modification factor, R, overstrength factor, Ω0, ductility ratio, μ, and median collapse capacity, S^CT, are evaluated. To this end, 6 three dimensional diagrid structures with various heights and diagonal angles are modeled using OpenSees program and are equipped with BRBs in a novel arrangement. Utilizing nonlinear static analysis, the seismic performance factors of models are evaluated. Subsequently, the median collapse capacity (S^CT) of the models are determined by performing... 

There are several perturbations that force the satellite orbit to deviate from the elliptical form. To cope with these perturbations, station keeping is applied. For accurate station keeping, determination of the true satellite orbit is necessary. Radio interferometry is one of the techniques used for determining azimuth and elevation look angles of a satellite. In this paper we introduce three structures based on interferometry for determining the view angles of satellites .The estimated angles are combined with range measurement for orbital positioning of geostationary (GEO) satellites. In the proposed interferometry structures, to acquire the required angular accuracy, the distance... 

A cyclic simple shear device was modified for testing coarse-grained soils at unsaturated conditions. A combined methodology of controlling suction for the practical range of coarse-grained soil water retention curves was adopted. Water head control method was used to accurately control suction within capillary and transition zones of such soils. The axis translation technique, on the other hand, was employed as a complementary approach to reach higher suction values within residual zone. In order to evaluate the performance of the new setup, independent cyclic tests were carried out at various initial suctions including all key points and zones along the primary drying path. The analyses of... 

There are several perturbations that force the satellite orbit to deviate from the elliptical form. To cope with these perturbations, station keeping is applied. For accurate station keeping, determination of the true satellite orbit is necessary. Radio interferometry is one of the techniques used for determining azimuth and elevation look angles of a satellite. In this paper, we introduce three structures based on interferometry for determining the view angles of satellites. The estimated angles are combined with range measurement for orbital positioning of geostationary (GEO) satellites. In the proposed interferometry structures, to acquire the required angular accuracy, the distance... 

Localization of an emitting or reflecting target is one of the most important issues in a wide range of applications including radar, sonar, wireless communication and sensor networks. Due to significant effect on the positioning accuracy, designing the optimal sensor-target geometry has been considered as an important problem in the localization literature. The existing sensor placement methods mainly solve the problem in the cases without any constraints on the sensors locations. In the realistic scenarios, however, the sensors cannot be placed simply in arbitrary locations due to such constraints as the geographical limitations, communication problems between the sensor pairs and the... 

The Savitzky-Golay (SG) filtering is a widely used denoising method employed in different applications. The SG filter has two design parameters: the window length and the filter order. As the window length increases, the estimation variance is reduced, but at the same time, the bias error is increased. In this article, we obtain the optimal window length of an SG filter with an arbitrary order, based on minimizing the mean square error (mse), a well-known performance measure considering both the estimation bias and variance. To achieve the optimal window length, we propose an algorithm the performance of which is much better than the existing methods. In this article, we follow the viewpoint... 

The sensor-source geometry has a significant effect on accuracy of source localization problems. In a sensor placement problem, one attempts to optimally place the sensors in the surveillance area so as to optimize a performance criterion. Sensor placement methods mainly solve the associated problems without taking any specific constraint on permissible location of sensors into account. In practical applications, however, possible location for deployment of the sensors are subject to such limitations as environmental, industrial, and communication constraints, which affects the optimal sensor-source geometry. In this article, we consider the problem of optimal sensor placement, based on time... 

In this article, localization of a maritime target using a passive multistatic radar system, consisting of a single receiver and a number of satellites as its transmitters, is investigated. The set of communication satellites and also the global navigation satellite system (GNSS), including GPS, Glonass, and Galileo, are employed as illuminators of opportunity. In the receiver, the reflected signals from the target along with the direct signal from the satellites are employed to extract a set of bistatic range measurements. Leveraging these measurements and the satellite's position information, a novel localization method considering zero height of maritime target and appropriate combination... 

A new level converter for use in dual voltage SOI digital circuits is presented. This technique uses the idea of keeper transistors, and consumes less power compared to the traditional methods. The effects of load capacitance on the circuit are studied by extensive simulations. © 2006 IEEE  

Ground improvement techniques are inevitable for weak soils that cannot endure the design load imposed by superstructures. Deep mixing technique (DMT) as one of these methods is promising and effective when a deep soil layer with low bearing capacity is encountered. Such deposits are quite common in the South-west of Iran where the studied site is located. In order to validate the influence of DMT on the enhancement of strength, both in-situ and laboratory tests were conducted. Afterwards, a parametric study was carried out to investigate the influence of key factors including cement content, water–cement ratio, curing time and plasticity index (PI) on the performance of DMT. In summary, a... 

Ground improvement techniques are inevitable for weak soils that cannot endure the design load imposed by superstructures. Deep mixing technique (DMT) as one of these methods is promising and effective when a deep soil layer with low bearing capacity is encountered. Such deposits are quite common in the South-west of Iran where the studied site is located. In order to validate the influence of DMT on the enhancement of strength, both in-situ and laboratory tests were conducted. Afterwards, a parametric study was carried out to investigate the influence of key factors including cement content, water–cement ratio, curing time and plasticity index (PI) on the performance of DMT. In summary, a... 

In the present study the behavior of Ti-Al-C ternary system is investigated during mechanical alloying. The mixture of Ti, Al and C powders was used with initial stoichiometric composition of Ti3AlC2. X-ray diffraction (XRD) was used to characterize the milled powders and a thermodynamic analysis of the process was then carried out using Miedema model. This thermodynamic analysis showed that for all binary Ti-C, Al-C, Ti-Al systems and ternary Ti-Al-C systems, among all compositions, the thermodynamic driving force for intermetallic phase formation is much greater when compared with the formation of solid solutions or amorphous phases. Finally the reactions that are feasible to occur during... 

Real-time measurement of soil water pressure has been recognized as an essential part of investigating water ow in unsaturated soils. Tensiometry, amongst di erent measuring techniques, is a common method for direct evaluation of water pressure. However, the lower limit of measurable water pressure by a conventional tensiometer becomes even more limited by increasing its length in the vertical installation. This paper describes the development of a Vacuum-Re lled Tensiometer (VRT) for monitoring soil water pressure independent of installation depth. This is achieved by xing the distance between pressure sensor and ceramic cup together with incorporating an ancillary vacuum-re lling assembly... 

Real-time measurement of soil water pressure has been recognized as an essential part of investigating water ow in unsaturated soils. Tensiometry, amongst different measuring techniques, is a common method for direct evaluation of water pressure. However, the lower limit of measurable water pressure by a conventional tensiometer becomes even more limited by increasing its length in the vertical installation. This paper describes the development of a Vacuum-Refilled Tensiometer (VRT) for monitoring soil water pressure independent of installation depth. This is achieved by fixing the distance between pressure sensor and ceramic cup together with incorporating an ancillary vacuumre filling... 

An efficient method has been developed to construct 3-formyl-2-thioacetamide-indoles via a one-pot, two-step procedure involving condensation of isocyanides with indolin-2-thiones to give a 3-aminomethylene-indolin-2-thione intermediate, followed by regioselective reaction with chloroacetylchloride and subsequent hydrolysis  

Evaluation and control of suspended sediment load as one of the main water quality concerns is important in large basins, especially in basins with planned dam construction. Success in sediment control measures depends, in particular, on proper identification of sediment sources. Since observations alone are normally not adequate for source prioritization/contribution in relation to the downstream sediment loads, hydrological simulation tools may be applied for spatial prioritization of runoff and sediment yield in basins. In this paper, subbasin prioritization was conducted for the Gharasu basin, located in southwestern Iran. Soil and Water Assessment Tool (SWAT) model was calibrated and...