Sharif Digital Repository

Today, with increasing population and technological advances, the use of energy and fuel has greatly increased, and since the main source of energy supply in the world is fossil fuels, this increase plays a significant role in air pollution, climate change and the most importantly environmental degradation.One of the basic methods whose technology has developed rapidly in the last decade is the use of fuel cells to supply electricity and heat simultaneously electrochemically. In this method, which can be considered as reverse electrolysis, the chemical energy stored in fossil fuels is extracted without combustion. These systems are more efficient than other methods and produce very little... 

Data mining is the process of extracting information from large data sets using algorithms and methods derived from the field of statistics, machine learning and database management systems. Data mining, popularly known as knowledge discovery in big data, enables companies and organizations to make informed decisions by collecting, aggregating, analyzing and accessing company data. The pharmaceutical industry is one of the most important levels of the drug supply chain, which has a significant impact on the healthcare sector of any society. In this context data mining can be used in various procedure such as discovery of a new medicine, sequential registration of clinical trials, combining... 

We study the problem of preclustering a set $B$ of imprecise points in~$\Reals^d$: we wish to cluster the regions specifying the potential locations of the points such that, no matter where the points are located within their regions, the resulting clustering approximates the optimal clustering for those locations. We consider $k$-center, $k$-median, and $k$-means clustering, and obtain the various results. Then we study the higher order Voronoi Tessellations as an important concept in clustering area. Generalizing Lee’s inductive argument for counting the cells of higher order Voronoi tessellations in $\Reals^2$ to $\Reals^3$, we get precise relations in terms of Morse theoretic quantities... 

This paper aims at producing surrogate models which can predict building structural response under ground motion loads. Rapid response prediction has a great influence on post-event decision-making. The current study follows mentioned purpose in two main sections. The first section proposed deep models, able at estimating displacement time-series response by using only ground motion and roof acceleration. By this point, different preprocessing methods and their effects are studied. Also, a novel loss function is introduced and a hybrid model consists of different deep layers utilized to gain accurate models. These models train and evaluate on two case-study buildings; a special moment frame... 

Let be a sub-semigroup of SL(d;Z) which acts strongly irreducible on Rd, i.e. there is not any invariant finite union of nontrivial proper subspaces of Rd. acts on Td by homeomorphisms. We will show that under these assumptions every infinite invariant subset of Td under the action of is dense in Td. For instance, if x is a point in Td which is not rational, then x = Td. In this thesis, we will follow the method of Y. Benoist and J.F. Quint for proving such results. Their method is to prove some kind of rigidity for the stationary measures for the action of on Td. Actually, every atomless stationary measure is the lebesgue measure on Td which is invariant under all the elements of... 

We study the expected value of stopping times in stochastic processes. Since there is no rigorous solution for computing stopping times in many processes, our approach is based on estimation using well-known methods in the Reinforcement Learning literature. The primary method in this research is the temporal difference algorithm. With some modifications, we can study the role of some state features in determining the stopping time. Moreover, without a complicated mathematical analysis, we can find functions closely enough to the goal function.Furthermore, we compare our proposed algorithm to the well-known regression methods and show our algorithm's advantages and disadvantages. The primary... 

In this project, two types of graphene obtained from chemical and chemical vapor deposition (CVD) methods were studied for gas/vapor sensing applications . In chemical method, oxidation and exfoliation of graphite was performed in liquid phase. AFM, XPS, Raman spectroscopy and Uv-visible spectroscopy were indicated that single layers synthesis of graphene oxide (GO) sheets was formed successfully. Reduction of the GO to reduced graphene oxide (RGO) was chemically done by hydrazine as a conventional reducing agent and melatonin as a green alternative. Photocatalytic reduction and hybridization of GO with TiO2 was also studied. TEM, SEM and AFM analyses confirmed nucleation and growth of TiO2... 

This thesis has developed a novel platform for digital dentistry which facilitates the interoperability among different digital components and improves digital workflow in a collaborative environment. The platform is inspired by the cloud manufacturing paradigm for enabling the interoperability and collaboration management and also applies the DICOM standard to improve the integration for the coordination among the different stakeholders for better sharing of their resources while they are geographically distributed. The paper has proposed the application of the PACS concept to include design, implant planning, process planning and production workstations. The paper has conducted a... 

With the advent of the Industry 4.0 and advances in Information Technology, the manufacturing systems have experienced great evolution and transition in their production paradigms. Among these developments, we can refer to the globalization process of resources and a diversion from mass production to the production that is based on customized orders. Likewise, a movement from product-based manufacturing towards service-based production is taking place. Such changes expose supply networks to new opportunities and threats and encourage them to exploit advanced production systems. Cloud manufacturing, as an approach to fulfill the state-of-the-art opportunities, has been recently considered by... 

Behavioral economics demonstrates that the sentiment can affect the behaviors and financial decisions of people. Can this be generalized to societies? For instance, is it possible for societies to experience emotions that will change their ways of decision making? This thesis attempts to perform an experiment addressing these questions. Bitcoin has been facing a transient phase of price volatilities. Many articles believe that bitcoin does not have an inherent value and is only derived by factors like the perception and acceptance of it and the sentiments among the investors. Digital currencies provide the unique possibility of measuring socioeconomic signals using digital traces.The... 

Organizations in the oil and gas industry often deal with a variety of logistic challenges. These organizations need to utilize innovative technologies like machine learning and other IT-based technologies to reduce costs and help achieve a lower-emissions environment. These industries involve a global supply chain comprised of domestic and international transportation, inventory control, materials handling, import/export facilitation, and information technology. Currently, in these industries, a classic model for executing supply-chain management techniques is considered. However, companies can optimize their supply chains to generate more productivity for better financial returns. Applying... 

Networks and the epidemiology of directly transmitted infectious diseases are fun-damentally linked. The foundations of epidemiology and early epidemiological models were based on population wide random-mixing, but in practice each individual has a finite set of contacts to whom they can pass infection; the ensemble of all such contacts forms a network. Knowledge of the structure of the network allows models to compute the epidemic dynamics at the population scale from the individual-level behaviour of infections.Motivated by the analysis of social networks, we study a model of random net-works that has both a given degree distribution and a tunable clustering coefficient.We consider two... 

In the traditional process planning, the expert decides upon the production process for a product by considering the previous cases and by decomposing, analysis and interpreting the shape of the product in terms of more familiar previous cases. In recent decades and by developments in the disciplines of the artificial intelligence, mass customization, cloud manufacturing and additive manufacturing, a necessity for process planning systems which need less human intervention by intelligent interpretation of the shape and consideration of the available data from previous productions, has emerged. Inspired by the traditional process planning by human expert, and considering the overall process... 

Recently, nanotechnology has promised to create and/ or improve therapeutic methods which in turn remain minimum side effects by employing synergistic effects of nanostructures. However, a comprehensive understanding of the interactions between nanostructures and building blocks of the biological systems (cells) is essential to create innovative therapeutic methods and compound and also predict their behavior for upcoming applications. In this thesis for the first time, synergistic effects of graphene-nanobubbles in interactions with bacterial (as the simplest model) cells were investigated. Therefore, at the first step, production of nanobubbles (NBs) in the presence of two-dimensional... 

In recent years, cloud manufacturing as a successful business model has attracted a lot of attentions. Many papers and researches have discussed various aspects of cloud manufacturing. Despite of enourmous works in this area we can categorize them using the view to the manufacturing platform. According to the authors’ researches, almost all of the the researchers looked to the system in a centralized manner with private structure. A structure in which a central unit decides for all and seeks to optimize its intended objective function. In private platforms, a central unit which is usually the owner of the company, makes decision for its all subsideries. But, public platform has a different... 

Triboelectric nanogenerator (TENG) works based on the accumulation of electrostatic charges produced on the surface of two dissimilar materials while they are brought into physical contact. When the surfaces are separated by a mechanical force, the induced triboelectric charges generate a potential drop, which can lead to generate an electrical current. Since their invention in 2012, TENGs have shown a rapid development in diversity of structure, amount of output power and range of applications, such as self-powered sensors, touch pads, and smart skin. Various kinds of mechanical force can be used for producing electrical energy: human motion, walking, vibration, rotating tire, wind, flowing...