Sharif Digital Repository

Human as an important part of the natural environment and can exert their positive or negative effects in the form of long-term and short-term on a natural environment. Human impacts on the natural system are very complex and consist of various components. The most considerable among them from past to now are maybe land use and land cover change, although, the impact of dam construction, water pollution, air pollution and etc, can not be neglected. To quantify the impact of these changes, many researchers have studied meteorological and climatic parameters using statistical relationships, but one major problem always existed, the low spatial accuracy of meteorological data. In recent years,... 

The competition between producers and the contracts issues between the producers and consumers of electrical energy in restructured power systems might cause on unwanted increase in power interchange beyond transmission lines capacity. If the power interchange is not well-managed, it would often cause overloads in specific path. This phenomenon is termed as lines congestion. The major goal of congestion management is to create a set of rules that ensure sufficient control over producers and consumers to maintain an acceptable level of power system security and reliability in the time of limitation of transmission network with maximizing economic market efficiency. As FACTS devices provide... 

Usually in analysis of arch dams, applied seismic motions on dam-foundation interface are assumed to be uniform. This is while that recorded motions show non-uniform accelerations in dam-foundation interface. Analyzing of the dam under this non-uniform accelerations we can find the importance of this assumption in analysis of arch dams. Two earthquakes were excited “KAROON III” dam at 20.11.2007 and 21.11.2007. The respective motions were recorded by the array of accelerometers that has been installed on the dam. The recorded motions, indicated non-uniformity of excitations in accelerometers were installed near the dam-foundation interface. Therefore this data provided an opportunity to... 

The paper aims to investigate the importance of firms’ financial constraints for pricing equity in Iran. We study the impact of financial constraints of non-financial firms on their stock returns using a sample of 241 manufacturing firms listed in Tehran Stock Exchange (TSE) for the period of 2007 to 2014. We use a similar index as in Kaplan and Zingales (1997), KZ, to measure financial constraint. We examine whether financial constraint influences stock returns and can improve the explanatory power of the Fama and French three-factor asset pricing model. Our findings indicate that financial constraints can be considered as an important factor affecting asset returns. Cross-sectional... 

Currently, the use of robots and microrobots in medical applications has significantly increased due to their extensive and unique capabilities. One such application involves the utilization of magnetic continuum robots controlled by an external magnetic field in minimally invasive surgeries. This research focuses on discussing methods for effectively controlling magnetic-continuum robots and applying external magnetic fields. Two primary methods for applying the external magnetic field are explored: the use of electromagnetic coils and permanent magnets. Based on these methods, systems for applying the field and controlling the magnetic continuum robot have been constructed and... 

In this study, effect of chelate ligands containing carboxylic, phenolic, and amine functional groups on the synthesis of related-perovskite Ca2Fe2O5 versus perovskite CaFeO3 structures have been investigated. Herein, the application of chelating-agent method, e.g. EDTA, Citric Acid, NTA, malonic acid, maleic acid, catechol, acetylaceton, p-tert-butycatechol, aminophenolic derivative ligand, and 2-hydroxyiminodiacetic acid, in comparison to co-precipitation method was also undertaken. The crystalline structure of the obtained perovskites were compared with those of co-participation method in solid state. Experimentally, it was found that the related XRD bands for CaFeO3 were appeared in the... 

Electrochemical treatment of tumors introduces cancer therapy method that uses direct current which passes through cancer tissue. The manipulated variable (direct current density) is applied to the surface of the electrode. As a result of applying direct current on the anode's surface, two competition reactions start to happen on the electrode's surface, Chlorine and Oxygen evolutions. The productions of these two reactions for instance Cl_2 , Cl^- and H^+ caused different reactions in the domain of the electrolyte which is the body tissue. According to the buffer characteristic of blood and organic features of tissue, various types of acids like HClO form in the electrolyte. If the pH in... 

In the past decades, hydrogels have been used as an adsorbent with high potential to remove pollutants in water. Hydrogels are three-dimensional polymer networks that have the ability to absorb and store water and water-soluble compounds due to the presence of hydrophilic functional groups in their structure. Different particles with unique characteristics can be used to increase the efficiency of hydrogel absorption. Based on the type of pollutant, hydrogels are divided into three different forms, including particles, films and nanocomposites. In this research, the absorption effect of metal cations as well as the absorption kinetics of polyvinyl pyrrolidine-based hydrogels, sodium...