Sharif Digital Repository

Knowing different groups of customers and building effective communication with them in such a way as to guarantee the future economic interests of the organization is a very important issue in today's businesses. The attraction of profitable customers, as well as the preservation of valuable old customers, are both important, except for the precise identification of their features. The value of customer longevity plays an important role in customer segmentation, and there are numerous researches that focuses on customer value with the aim of making more profit for the organization, most of which have life-cycle customer value models as the main inputs for segmentation cCustomers have been... 

Understanding the flow of liquids and particularly water in nanochannels is important for scientific and technological applications, such as for filtration and drug delivery. In this study, we perform molecular dynamics simulations to investigate the transfer of single-file water molecules across straight or nonstraight single-walled carbon nanotubes (SWCNTs). In contrast with the macroscopic scenario, the nonstraight nanostructure can increase the water permeation. Remarkably, compared with the straight SWCNT, the nonstraight SWCNT with the minimal bending angle of 30° in the simulations can enhance the water transport up to 3.9 times. Also increasing length and diameter of carbon nanotubes... 

There has been a noticable surge in the usage of machine learning techniques in various fields, such as security related fields. With this growing pace of using machine learning to solve various problems, securing these models against attackers has become one of the main topics of machine learning literatures. Recent work has shown that in an adversarial environment, machine learning models are vulernable, and attackers can create carefully crafted inputs to fool the models. With the advent of deep neural networks, many researchers have used deep neural networks for the task of malware detection, and they have achieved impresive results. Finding the vulnerlabilities of these models is an... 

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... 

Identification protocols facilitates two participants A and B to identify themselves to each other. Beside identification, A and B can exchange a secret value along with the identification process as the key exchange identification protocol.A secure key exchange identification protocol hould utilize perfect forward secrecy (PFS) property. PFS means if an attacker could compromise an entity in future and gain its long-term key, he cannot succeed to extract previous session keys. So, he will be unable to decrypt previous messages and they will remain secure. Because of the low power and storage of light devices, updating secret shared keys is a solution to reach PFS in such protocols. A major... 

In this thesis ship propeller performance in maneuvering conditions have been investigated which means an oblique flow condition for working propeller. Then results of these investigations have been put to use to simulate maneuvering using MMG equations. These calculations have been done to investigate nominal wake variations in different drift angles and depth conditions. In this project displacement vessel KVLCC2 and propeller POTSDAM VP1304 have been studied due to the abundance of experimental data. Calculations in this study have been carried in three steps: 1, calculation of nominal wake of the vessel in different drift angles and depths via CFD. 2, Using the results of previous...