Sharif Digital Repository

Over the past several decades, human activities have resulted in a significant increase in surface and ground water pollution. Human activities have caused significant pollution of surface and groundwater, with pollutants like nitrates, phosphorus, heavy metals, toxins, and chemical fertilizers degrading water quality. In order to control pollution and reduce the concentration of pollutants in water, it is necessary to use appropriate numerical criteria to evaluate and manage the quality of water resources. The water quality index, as a scoring method for investigating the combined effects of independent parameters on overall water quality, is a widely-used metric for measuring the quality... 

It is inevitable to simulate the phenomena that govern nature to make decisions and policies on water and environmental issues. Therefore, researchers have tried to make a good prediction of water's quantitative and qualitative status by using modeling and computer processing power. One of the primary and essential issues in modeling is using sensitivity analysis techniques. Using this knowledge, much information will be obtained on how to influence the model's output regarding various factors such as parameters, input data, and initial and boundary conditions. Global sensitivity analysis based on variance as one of the most well-known and, at the same time, the most widely used sensitivity... 

This study investigates the seismic demand in diaphragms, chords and collectors in typical floor systems used in steel structures. These systems include joist-block slabs, open web steel joists, and composite steel decks. The lateral load resisting systems considered were Special Concentrically Braced Frames (SCBF) and Special Moment Frames (SMF) of varying heights. For each system, the influence of using shear connectors for perimeter beams, joist orientation, geometric configuration, and number of stories on lateral force transfer was examined. Nonlinear static and time history analyses were conducted on selected models. Key findings are as follows:
• In joist slab system without shear... 

Water quality is a fundamental pillar of public health, sustainable development, and food security, and monitoring pollutants such as total phosphorus (TP) plays a crucial role in the effective management of surface water resources. Phosphorus is an essential element for agricultural production; however, its loss from soil to aquatic systems can lead to environmental issues such as eutrophication, biodiversity loss, and degradation of water quality. Although monitoring TP concentrations is vital for effective water quality management, many countries face a lack of sufficient and consistent data. Numerical models, particularly data-driven approaches based on machine learning, can help bridge... 

Opportunistic spectrum access in cognitive radio networks has introduced multiple challenges in the realization of this technology. One of these key challenges is spectrum mobility, in which a secondary user (SU) must be able to vacate channels upon the appearance of a primary user (PU) and reestablish a communication link to avoid service termination, known as spectrum handoff. For a connection-based modeling, multiple interruptions can occur, which lead to multiple handoffs; hence, in a proactive approach, a sequence of target channels, rather than a single target channel must be determined. The first parts of this thesisis dedicated to the analysis of a time-slotted cognitive radio, in... 

The present thesis introduces a new method to design non-fragile controllers. The idea of design is to set the centroid of the stability region as the tuning point of two-parameter controllers. This ideahas been motivated by the fact that the centroid of a convex region belongs to a set of pointsthat have farthest distance from its boundary. In case that stability region is not convex, a correction may be needed because the centroid of non-convex region may be very near to or out of its boundary. One modified version of design method when stability region is not convex, is to find maximum convex sub-area inside stability region and set its centroid as the tuning point of controller... 

Phosphorus is a key nutrient in the Earth's biogeochemical cycle and plays a crucial role in agricultural productivity and global food security. It is primarily utilized in the manufacture of chemical fertilizers. At the global scale, phosphorus concentrations in surface waters are regulated by a complex interplay of environmental, climatic, and anthropogenic factors. Excessive phosphorus input into aquatic systems, particularly through agricultural runoff and industrial wastewater, can lead to eutrophication, water quality degradation, and serious ecological issues. Understanding the drivers of phosphorus concentration on a global level is therefore essential for sustainable water resource...