Sharif Digital Repository

Most of dynamical models in the real world, have various restrictions and complexities in their structures. These constraints make the controller design much more difficult. In this work, it has been tried to design the controller for two kinds of common dynamical systems in the presence of these restriction by using the fuzzy logic systems. Several restrictions are investigated in this project such as unknown dynamic of the model, unmeasured state variables, unknown control directions, existence of time delay in the input and the state variables, input saturation and controller singularity.The backstepping technique and the dynamic surfaces control approach have been used to design the... 

The most common form of communication on the internet and social network websites is text messages. normally communication on social media or even on the web is by posting some sort of text. usually, these messages or posts are short and text used in them may not follow any language standards, this makes it very difficult to process them. Different age groups use a certain language differently and this is shown in the way, each of them writes texts. The advancements made in the field of natural language processing and computational linguistics makes it possible to predict, text authors age groups by analyzing the way they write. This study focuses on ways to automatically recognize the age... 

One of the lesser-known issues in the modeling literature of assortment optimization issues is the assortment optimization for reusable products, which is an issue in various areas, including offering parking space, renting cloud computing systems resources, and rental of fashion products, etc.In this issue, we are faced with a high diversity product rental store that has a customer in each period. The seller offers a limited set of products depending on the customer demand and the inventory in hand. He can decide to rent the product or leave the system without renting the product. In case of renting the products by the customer, he may return them until the end of this period or keep them... 

A key driver of the overall productivity and profitability of a supply chain is its distribution network which can be used to achieve a variety of the supply chain objectives ranging from low cost to high responsiveness. Designing a distribution network consists of three subproblems: location–allocation problem, vehicle routing problem, and inventory control problem. Because of high dependency among these problems, in the literature there are several papers integrating two of the above problems: location–routing problems, inventory–routing problems, and location–inventory problems.
The three echelon location routing inventori problem (LRIP) is raised by the design of transportation... 

Lithium is one of the most commonly used metals in industry with a wide variety of applications including batteries, lubricating grease and pharmaceutical products. Demand for lithium is expected to rise with the increasing adoption of electric vehicles. Market reports have predicted that world lithium demand will increase by 2.5 times from 2010 to 2020. Therefore, there is a pressing need to develop new sources of lithium to support this anticipated increase in demand. Lithium can be extracted from salt brine and lithium containing minerals as lithium compounds.
Salt brines are the most abundant lithium sources available in the world, comprising about 60% of all known lithium deposits.... 

This research presents scheduling of several different projects in supply chain environment which activities of these projects are performed by some contractor companies. A new practical model for solving project scheduling problem in supply chain environment is present. Multi renewable resource presents in the model of research. The research proves that the model is NP-Hard. A genetic algorithm and a simulated annealing algorithm are proposed for solving the model. The parameters of genetic algorithm such as the number of steps, the number of mutation in each step, the number of crossover in each step, the number of generation phase and also the parameters of simulated annealing algorithm... 

This research intends to investigate the multi-skilled project scheduling problems (MSPSP) considering staffs’ dynamic efficiency. In doing so, a mixed-integer nonlinear programming (MINLP) model is proposed, considering the influence of personnel learning and forgetting on activities duration. The more the staff spends time on their various skills, the more learned and efficient they will be on that skill (according to personal learning curves) so that they can complete new tasks less costly and more quickly. Most project-based organizations want to maximize value by finishing the projects efficiently and developing their staff’s competence through projects. Inherently, any... 

Urban transportation is one of the key parameters and indicators that determine the sustainable development of the city, in other words, to understand and evaluate the sustainability of a city, its transportation system must be considered. Bicycles can be considered the most sustainable means of urban transportation not only for short trips but also for medium trips.Urban bike networks in major cities are being systematically serviced and, like any other system to manage this volume of events, are facing challenges that we aim to improve one of the major costs of this system. The biggest challenge we face on this network is the imbalance between Inbound and outbound bicycles at different... 

Supersonic inlets, as one of the most important components of fighter aircraft, are designed to provide the required airflow with an acceptable level of energy and quality and with a minimum drag. From the inlet design point of view, there exist various configurations that are based on different criterion such as supersonic flow compression region, flow dimensions, and installation position, to name a few. The flight Mach number, M∞, could further complicate the design and structure of these types of inlets. One of the requirements for minimum drag is that at supersonic speed the shock wave that forms in front of the inlet must impinge on the cowl lip, called shock on lip condition (SOL). ... 

This study presents an experimental and numerical investigation on the compressive behavior of a new type of composite column which consists of both solid and hollow concrete-filled UPVC tube with and without GFRP wraps.Composite construction has been often more economical than traditional concrete construction, because this system realizes the most effective use of concrete, and composite members in the structural system.The enormous potential of using plastic tubes in composite systems will be illustrated by this research. It is an economical type of column in construction.This research aims to study the behavior of UPVC-confined columns under axial compression. A sum of 132 specimens are... 

In this research a mathematical formulation is presented for project scheduling problem subject to non-renewable perishable resources where the objective is minimize the cost of ordering and maintenance of resources. We use the framework of a resource constrained project scheduling problem (RCPSP) with finish-start precedence relations between activities and resources will be perished after a determined duration and must be procured. Resource procurement have ordering and purchasing costs and excess resources must be stored and have maintenance cost. There is a unique way to perform the activities and preemption is not allowed.
This work employs Genetics Algorithms to solve the problem... 

According to the unique characteristics and increased competition in Business-to-Business (B2B) exchanges, achieving customer loyalty is becoming more and more crucial in B2B marketing. Furthermore, with the advent of relationship marketing, it is important to sustain a long term relationship with customers.Thus, the major issue is to examine what influences a customer’s willingness to remain with the existing supplier. The purpose of this study is to identify the antecedents of customer loyalty in a Business-to-Business context. Based on the relevant literature on customer loyalty and satisfaction, a conceptual model is developed to assess the most influential drivers of loyalty. The... 

Zinc oxide thin films due to special specification and properties have variable application in different industries. Recently because of wide application of zinc oxide doped SiO2 in optoelectronics and sensors, lots of investigation have been focus on it. Meanwhile due to the SiO2 hydrophilic properties, doping of ZnO with SiO2 can improve self-cleaning properties zinc oxide membrane.It this project zinc oxide and ZnO doped SiO2 thin films with different composition were made by sol-gel and dip-coating process used for coating of mentioned sol over the quartz surface(15*25 mm). At first point different sol with different components was mixed with each other to make composite films but due to... 

Today a significant portion of the world magnesia supply is produced by approximately 20 manufacturers by precipitation of magnesium hydroxide either from seawater or brine sources, which amounts to about 14% of the world magnesia production. The first synthetic magnesia production occurred along the French coast of the Mediterranean Sea, near Aiques-Mortes, operating sometime before 1885. Magnesium hydroxide was precipitated from seawater by reacting it with milk of lime in a continuous fashion using three sequential agitated reactors. Because of the abundance of brine resources enrich in Magnesium in our country, in this project, was tried to precipitate Magnesium Hydroxide from brine... 

In the present project, in order to be self-sufficient and optimal use of boron mines in Iran, a study entitled “The effect of process variables on the production of boric acid” has been conducted, This project has two main objectives: the first objective is the production of boric acid from boron sources and mines in Iran and the second objective is to analyze the effect of variables such as temperature, time, acid concentration, solid to liquid ratio and particle size on the purity of boric acid produced. And finally achieve the optimal conditions for the production of boric acid.In this study, boric acid was made from leaching hydrobracite (magnesium-calcium ore with boron) with sulfuric... 

Rewarding system is one of the most important and basic subsystem of human resources and it is one of the main concerns of the managers in any organization, since an appropriate bonus payment system increases motivation and efficiency of individuals and vice versa an inappropriate rewarding system provokes frustration in staff .Rewarding system is more important in project-oriented organizations because the most influential factor in the success and profitability of the organizations is motivated employees. The basic question in this study is that what kind of payment reward a project-oriented organization should have in order to get its employees motivation and ultimately make the... 

In this work, polyvinylidene difluoride (PVDF) as a ferroelectric polymer, polyaniline (PANI) and polypyrrole (PPy) as conductive polymer additives are used to fabricate high performance mesoporous CH3NH3PbI3-xClx mixed-halide perovskite solar cells in a sequential deposition method. Using polymer additives in perovskite precursor solution leads to modification of perovskite layer morphology by changing nucleation and growth of perovskite grains. Besides, conductive polymer additives in perovskite layer help to more charge carrier transfer. Power conversion efficiency has been enhanced from 10.40 % to 16.51% and to 13.21 % in ambient atmosphere in the presence of 1.0 wt. % of PVDF and PPy... 

Vibration based energy harvesting is the process of trapping and collecting vibrational energy from ambient sources which seem unusable at first sight. The smart materials with the capability of coupling two different fields can be used in converting vibrational energy to electrical one. One of this smart material which has been taken into account recently is the Magnetic Shape Memory Alloy (MSMA) and it can couple the magnetic and mechanical fields. In MSMAs the total magnetization vector changes with the application of stress and make it possible to harvest energy from Faraday law’s of induction. An important phenomena that exist in MSMA is the dependency of magnetization-strain behavior... 

One of the basic resources for lithium extraction is brine which is very abundance in Iran. It is important to characterize these brines and their compositions to select a suitable method for lithium recovery from them. By investigation of the local brines and determining lithium and other alkali metals composition in them, the ion exchange process using titanium dioxide ion-sieve with nanotube morphology is suggested as highly effective method for lithium extraction from Iranian brines. Due to high advantages of hydrothermal process, TiO2 nanotubes were produced by this method and the optimum parameters of hydrothermal reactions were reported. In this way, hydrogen titanate nanotubes with... 

This study examines how imperfect advance load information (IALI) can improve profits and vacancies for a trucking company. To evaluate the value of IALI, first, a deterministic mathematical model is created. Next, we propose a Markov decision programming approach that can use this IALI.Due to exponential size of the state space the problem cannot be solved to optimality it in polynomial time so we suggest a heuristic algorithm.After designing a comprehensive set of experiments, we use both models using a dynamic implementation mechanism to evaluate the benefits of using this information. Statistical analysis and literature show that, firstly, the use of IALI can significantly improve the...