Sharif Digital Repository

Darrieus turbines are one of the most widely used turbines in extracting energy from tidal currents. This study aimed to investigate the effect of utilizing helical blades and variable solidity ratio on the efficiency of Darrieus tidal turbines. For this purpose, three types of helical turbines with different solidity ratios have been designed, and computer simulation has been used to investigate the effect of the mentioned parameters on the efficiency of the Darrieus turbines. According to the simulation results, the helical turbine has less efficiency than the straight blade Darrieus turbine. The maximum hydrodynamic efficiency of the Darrieus turbine with straighted blades is 38.5,... 

Theanine is a non-protein amino acid which was first isolated from tea plant leaves (Camellia sinensis) and also found in a mushroom named Xerocomus badius and some other Camellia species such as C.japonica and C.sasanqua. Theanine comprises about 50% of amino acids in tea and 1-2% of dry weight of tea leaves. It contributes to the umami taste and unique flavor to tea infusion and has many physiological and pharmaceutical effects such as anti-tumor and anti-cancer activity, neuroprotection, antihypertensive, relaxation, increased focus and anti-obesity effects. So this compound is essential for human body but is not synthesized in it and should be administrated orally. In recent years, study... 

Schiff bases are used as prevalent ligands in coordination chemistry and are prepared easily. Their application as mild inhibitory agents for prevention of various steel’s corrosion in acidic solution has been proved. When their structure is altered, multi-purpose application for them is found. This property has led to a motive for research and study. In this study, electronic properties of a group of Schiff bases are investigated. The goal of this study is using quantum mechanics (QM) as a tool for specifying electronic properties of some of these bases. With respect to QM calculation which is done by density functional theory (DFT), their properties as inhibitory agents are studied. First,... 

Up to early seventies, Gas turbine combustor design was very time consuming and costly process including trial and errors through test rigs. Over the time analytical-experimental relationships take place as one of the key rules in the design processes. With the increasing power of computer calculations, computational fluid dynamics find its way in the procedure. Obtaining a deeper understanding of flow conditions and geometry inside the chamber, a great reduction in production time and cost of revisions to rigs and samples were achieved. Finding a precise prediction of polluting elements like NOx (less than 10 ppm) after many run hours and enormous computing resources, CFD methods must... 

Fed-batch fermentation is a valuable and cost-effective method for bio-based production of various products such as ethanol, which has various applications in various industries.In recent years, bioethanol production has been given special attention in many countries. For this reason, the mathematical modeling of production of these products is very important for their optimal and cost-effective production. Given the transient and dynamic nature of fermentation and its specific complexity, mathematical modeling of fed-batch bioreactors is difficult and complicated. In this research, an unstructured model was used to predict the production of ethanol from blackstrap sugar cane molasses based... 

The rapid development of portable and wearable electronic devices has necessitated the creation of micro-sized energy storage devices, including micro-supercapacitors. Micro-supercapacitors are ideal energy storage sources for these devices due to their lifetime and optimal power density. Consequently, selecting the appropriate electrode material and developing a simple, low-cost manufacturing method for micro-supercapacitors present significant challenges. Graphene oxide, a key material for these applications, often underperforms due to its porosity and low specific surface area. However, its performance can be enhanced by integrating it with a new class of highly porous materials with a... 

By new advancements in vehicle manufacturing; vehicle quality evaluation and assurance has become a more critical issue. Today noise and vibration generated inside and outside a vehicle are more important factors than before. In present work, the vibration transfer path analysis and vibration path ranking of a car interior has been performed. The method is similar to classical multilevel TPA methods but has distinct differences. The method is named VIVS which stands for Vehicle Interior Vibration Simulation. Performance of some tests like chassis dyno test, virtual mass function test and body transfer function test are required in this approach. The accelerations on both sides of the engine...