Sharif Digital Repository

Land cover classification is one of the most important applications of POLSAR images. In this paper, a hybrid biogeography-based optimization support vector machine (HBBOSVM) has been introduced to classify POLSAR images of RADARSAT 2 in band C acquired from San Francisco, USA. The main purpose of this classification is to minimize the number of features and maximize classification accuracy. The proposed method consists of three main steps: preprocessing, feature selection and classification. As preprocessing, radiometric calibration, speckle reduction and feature extraction have been performed. In the proposed HBBO, the combination of onlooker bee of artificial bee colony (ABC) and... 

The current study revealed the effectiveness of polypropylene (PP) fibers and cement to enhance the strength of black cotton soil. PP fibers and cement with different concentrations were mixed with black cotton soil. The strength of PP fiber and cement-based soil samples was measured in terms of unconfined compressive strength (UCS) and California Bearing ratio (CBR). Specimens for UCS and CBR tests were prepared at 2%, 4%, 6% and 8% of cement (by dry weight of soil) and seven percentages of polypropylene fibers i.e. 0.0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% and 0.6% (by dry weight of soil). Fourier transform infrared (FTIR) analysis confirmed the presence of polypropylene and cement contents in... 

The current study revealed the effectiveness of polypropylene (PP) fibers and cement to enhance the strength of black cotton soil. PP fibers and cement with different concentrations were mixed with black cotton soil. The strength of PP fiber and cement-based soil samples was measured in terms of unconfined compressive strength (UCS) and California Bearing ratio (CBR). Specimens for UCS and CBR tests were prepared at 2%, 4%, 6% and 8% of cement (by dry weight of soil) and seven percentages of polypropylene fibers i.e. 0.0%, 0.1%, 0.2%, 0.3%, 0.4%, 0.5% and 0.6% (by dry weight of soil). Fourier transform infrared (FTIR) analysis confirmed the presence of polypropylene and cement contents in... 

In the present paper, spatially variation input effects on seismic responses of arch dams have been studied. Recorded ground accelerations at the dam foundation interface of Pacoima dam during January 13, 2001 were used for the purpose of this investigation. A numerical finite element model was developed for dynamic analysis of the dam reservoir system. The modified version of NSAD-DRI finite element program was used for the analysis and the ground acceleration time histories were interpolated at all dam foundation interface nodal points. Total and pseudo static displacements as well as developed stresses due to uniform and non uniform excitations are obtained. The results reveal that... 

The current study aims to assess the influence of EPS beads inclusion on the strength properties of stabilized poorly-graded sands. Various contents of zeolite and cement as stabilizing agents, with the total amounts of 4, 8, and 12% by dry soil weight, and also 0, 0.25, and 0.5% weight ratios of EPS beads (η) are examined. Zeolite is opted among a variety of pozzolanic materials so as to replace a part of cement (0, 10, 30, 50, 70, and 90%) due to its superior environmentally friendly properties. The stress–strain behavior, unconfined compressive strength (UCS), peak strain energy (Eu), and California bearing capacity (CBR) of the zeolite and cement-treated sand-EPS beads mixtures are... 

Epistemic uncertainty in seismic hazard analysis is traditionally addressed by utilizing a logic-tree structure with subjective probabilities for branches. However, many studies have argued that probability is not a suitable choice for addressing epistemic uncertainties; in particular in addressing the background knowledge supporting the probabilities. In this regard, the application of imprecise probability (IP) is investigated. It is discussed that IP could provide a flexible tool for a more objective presentation of experts' knowledge. Moreover, the importance of addressing the strength of knowledge and surprises relative to knowledge in seismic hazard analysis along with methods to do... 

Epistemic uncertainty in seismic hazard analysis is traditionally addressed by utilizing a logic-tree structure with subjective probabilities for branches. However, many studies have argued that probability is not a suitable choice for addressing epistemic uncertainties; in particular in addressing the background knowledge supporting the probabilities. In this regard, the application of imprecise probability (IP) is investigated. It is discussed that IP could provide a flexible tool for a more objective presentation of experts' knowledge. Moreover, the importance of addressing the strength of knowledge and surprises relative to knowledge in seismic hazard analysis along with methods to do... 

A probabilistic method is presented for identifying the dynamic soil-foundation stiffnesses of building structures. It is based on model updating of a Timoshenko beam resting on sway and rocking springs, which respectively represent the superstructure and the soil-foundation system. Unlike those previously employed for this particular problem, the proposed method is a Bayesian one, which accounts for the prevailing uncertainties due to modeling and measurement errors. As such, it yields the probability distribution of the system parameters as opposed to average/deterministic values. In this approach, the joint probability density function of the parameters that control the flexible-base... 

This study presents a comprehensive review of the Land subsidence (LS) cases, as a worldwide environmental, geological, and global geohazard concern. Here, 290 case studies around the world mostly conducted in large metropolitan cities (e.g. Bangkok, Beijing, California, Houston, Mexico City, Shanghai, Jakarta, and Tokyo) in 41 countries were collected. The spatial distribution of LS characteristics (e.g. intensity, magnitude, and affected area), impacts, and influential factors are scrutinized. Worldwide attempts to remedy the crisis of LS were also investigated in this review. It is shown that the coastal plains and river deltaic regions are of high-frequent subsided areas around the world... 

In this study, the nonlinear seismic analysis of a typical three-dimensional concrete faced rockfill dam is reported. Three components of the Loma Prieta (Gilroy 1 station) earthquake acceleration time history are used as input excitation. The dam under study is considered as if it were located in a prismatic canyon with a trapezoidal cross-section. A nonlinear model for the rockfill material is used, and contact elements with Coulomb friction law are utilized at the slab-rockfill interface. Vertical joints in the face slab are also considered in the finite element model. A substructure method, in which the unbounded soil is modelled by the scaled boundary finite element method (SBFEM), is... 

Marine structures, as key elements in the global energy network, constantly are subjected to harsh environmental loading conditions. Therefore, reliable yet efficient structural control mechanisms are required to ensure their safe functionality and structural stability. In the present work, a novel hybrid structural control element for marine structures has been designed in which the superelasticity effect of shape memory alloy (SMA) and damping controllability of magnetorheological fluid (MRF), as smart materials, have been combined. The novel system does not require huge external energy for activation and in addition, the system has the ability to be tuned for variable loading conditions.... 

Iranian water authority has recently announced that one of the effective ways to avoid unprecedented high water consumption in Iran's agriculture sector is to increase water price. This paper analyzes the feasibility of this policy by using a hydro-economic approach with the aim to consider the role of water pricing in agricultural water management. Such an analysis was conducted through comparing price of water consumed for producing selected agricultural crops (i.e. wheat, sugar beets, onion, tomato, barley, potato, corn, alfalfa hay and watermelon) in a case study on two provinces (East Azarbaijan and West Azarbaijan) in Iran to that in the state of California (CA) in the USA. According...