Sharif Digital Repository

In this research, we focus on r-gather and (r; ϵ)-gather clustering. In the r-gather clustering, the input points are in metric space and must be clustered such that each cluster has at least r points and the objective is to minimize the radius of clustering. (r; ϵ)-gather clustering is a kind of r-gather clustering such that at most nϵ points can be unclustered. MapReduce model is one of the most used parallel models to process huge data and processes the input data in some machine simultaneously in parallel.In this research, we give a lower bound for the approximation factor of r-gather clustering in MapReduce model. This lower bound works in MapReduce model even an optimal algorithm... 

In this thesis we focus on the extraction of resonance modes in photonic crystal resonators. This work could be divided in two different parts: in the first part we apply the Galerkin’s method effectively to the two and three dimensional structures, in the second part that constitutes the main part of this thesis we derive transmission line models for these structures. Fist we derive transmission line models for resonators based on the point defect and line defect in two-dimensional photonic crystals. Then we generalize this model to the three-dimensional photonic crystals. Finally we apply the same approach to the coupled resonators and analyze the coupled resonator optical waveguide. In... 

Think of an Alpine hiker who because of avalanche and a blinding blizzard, is stranded on a desolate, mountain path facing a chasm. The hiker cannot return the way he came because of the avalanche, yet, if he stays where he is, he will freeze as the temperature plummets. The hiker’s only real hope is to jump the chasm. Knowing that exertion generally follows belief, the hiker realizes that his attempt will be half-hearted, diminishing his chance of survival, unless he brings himself to the belief that he can make the jump. In circumstances like these, one is clearly justified both in forming beliefs motivated by pragmatic reasons, and in suppressing beliefs (I cannot make the jump) motivated... 

The thesis at hand provides a comparative study of Kantian and Fichtean ethics. In the course of this study, the ethical theory of these philosophers will be analyzed through three stages of “Foundation of Ethics,” “System of Ethics,” and “Application of Ethics”: Foundation of Ethics seeks out human will as the sole possible ground for ethical theory of both Kant and Fichte; System of Ethics follows the endeavors of the two thinkers in deducing concept of ethics from this sole ground; and lastly, Application of Ethics introduces the ethical thoughts resulting from a Fichtean account of ethics. This thesis is mostly based upon studies of Allen W. Wood of the ethical thoughts of Kant and... 

Reducing noise, vibration and damage to the vehicle's passenger compartment was always a problem that has been investigatedin many researches. Here engine mounts as connecting members between engine and chassis play a big role. Because both of engine and road vibration put on it. Many studies have been done to optimize the engine mounts. As a result, many of hydraulic engine mounts with different variety of system control. But a few researches did about optimization of location and orientation of engine mounts. Therefore this project is to provide a process to optimize the location and orientation of engine mounts. The optimization process is First the dynamic equations of dynamic system are... 

In this thesis a smart anticorrosive pH-responsive coat was developed with layer by layer (LbL) technique in the assembly of SiO2/CTAB/PSS/HMTA/PSS/PEI/PSS. SiO2 nanoparticles were prepared from Matland Company (Iran) with average size of 24 nm. At first, the corrosion inhibition of HMTA for API 5L Grade B steel in 3.5 wt.% NaCl solution was investigated. Tafel polarization technique showed the optimum concentration of HMTA was 0.08 M with 92% corrosion inhibition efficiency as the morphology of coverage and adsorption on the steel surface was confirmed by SEM and EDS. AFM results showed the roughness of the surface decreased from 241 nm to 56 nm that is attributed to HMTA adsorption on the... 

In recent years, sparse representation has had a variety of applications in computer vision such as noise reduction, image reconstruction, classification and dimension reduction. In this project, we aim to provide a method of matching the keypoints obtained from the Scale Invariant feature Transform (SIFT) algorithm. In this algorithm is used descriptor instead of intensity . The proposed method, first, extracts the salient points from the images and learns a dictionary-based descriptors corresponding to the points. Then, using the dictionary, it obtains the sparse coefficients for each salient point by which, it determines the correspondence of the salient points in the two images using SVD... 

Representation learning refers to mapping the input data to another space, usually with lower dimensions than the input space. This task can be helpful in improving the performance of methods in downstream tasks, compression, and improving sample generation in generative models. Representation learning is a problem connected to information theory, and information theory's concepts and quantities are used widely in representation learning models. Besides, the representation learning problem is closely related to latent variable generative models. These models usually learn useful representations in their process of training, implicitly or explicitly. So, the usage of latent variable... 

The detection and on-site measurement of vanillylmandelic acid (VMA), homovanillic acid (HVA), and dopamine (DA) as key biomarkers for a wide range of neurological disorders, including neuroblastoma, is of significant importance. To date, several colorimetric sensors have been introduced with mechanisms based on nanoparticle aggregation or their coating with silver. However, these mechanisms have drawbacks such as sensitivity to environmental factors and probe toxicity. Therefore, there is a high demand for a robust and non-toxic colorimetric sensor that utilizes a novel approach for the effective monitoring of these biomarkers. In this study, a single-component multicolor probe was designed... 

The search for an empirically proven quantum theory of gravity is one of the greatest open problems of fundamental physics. Obstacles are formal and conceptual in nature. Our goal is to find a theory that somehow unites general relativity (Einstein's classical field gravity theory) and quantum field theory. In this research work, the problem of quantum gravity and the reason for its importance are investigated, as well as the proposed solutions; and what philosophical issues do these approaches and the issue itself create. Research has been carefully selected to remain managed in terms of size and content, however, some basic formalism is introduced to enter physics and the philosophy of... 

Black holes are theoretically significant because they are (ideal) entities fully described by just three properties: mass, charge, and spin. Their importance also stems from their unique status as spacetime entities with universal properties, including the event horizon and—when including the singularity—representing the boundary of space and time. Beyond their spacetime properties, black holes are also thermodynamic systems. Their behavior requires a theory that integrates both spacetime and thermodynamics. A black hole is something that requires both a theory of spacetime and a theory of thermodynamics to describe and explain its behavior. A consistent description of time, spacetime, and... 

The human need for reliable and accessible energy sources for household, industrial, transportation, etc. caused the discovery of the first oil well to move towards exploitation and use of this large, cheap and available energy source, accelerated. With the start of this movement, oil and its products in the last two centuries have quickly established themselves as a major part of the energy basket of most countries in the world. The entry of crude oil and its products into the energy industry has faced new issues and challenges for decision makers in this field. One of the most important challenges has been the planning and management of the process of distribution and transfer of petroleum... 

Community question answering are the systems in which users can propose their needs with asking questions. Moreover, they can share their own knowledge with the others by responding their questions. Widely spreading this sort of communities and growth of questions and answers has made some challenges. One of these challenges is finding an appropriate users who can answer questions. For instance, some user might ask a question and has to wait some times to receive another user's response. On the other hand, the users who have expertise in some fields have to spend time a lot seeking to find related questions. Therefore, expert finding systems are used to meet these needs.The main issue is... 

By “Analysis of Epistemological Justification of Inference to the Best Explanation (IBE)” I mean to examine whether the IBE argument can increase the probability of the truth of belief to the outcome of the argument or not. According to the Strong Version of IBE, this increase shows that the best explanation is more likely to be true, whereas according to the Weak Version the best explanation is more probable than its available rivals. The most influential arguments against these positions are: (1) The bad lot objection (BLO) according to which the idea that the best available explanations will be more likely to be true, presupposes that the truth is already more likely to be found among... 

In Naming and Necessity and Identity and Necessity, Kripke convinced many that there are necessary propositions which are knowable only a posteriori. Kripke’s examples of these propositions can be placed into three categories: 1) Some mathematical propositions like Goldbach’s conjecture (the conjecture that every even integer greater than 2 can be expressed as the sum of two primes) 2) Scientific truths like “Water is H2O”, “Gold has the atomic number 79”, etc. 3) Identity statements flanked on both sides with proper names; like “Hesperus is Phosphorus”, “Cicero is Tully” and the like (in the rest of this article, these three categories will be called, respectively, the first, the second and... 

In his Mind, Brain and Free Will, Swinburne introduces a new argument for substance dualism based on the synchronic unity of humans’ conscious experiences. He argues that the human body cannot be the substance of such a synchronic unity, and that this coexperiencing property, which is a mental property, is the essential property of the human substance: hence our substance is a mental substance. After providing a careful explanation of Swinburne’s subtle argument, I first try to demonstrate that it is metaphysically possible that the brain itself could instantiate such a synchronic unity without the need to presume another substance. Then I shall argue that it is unclear how to infer the... 

This dissertation consists of three chapters. In the first chapter, a description of formation of Darwin's theory of Evolution is expressed. After that, the process of formation of modern theory of Evolution, along with an explanation of the theory of evolution and the evidence for it was mentioned. In the second season, which is responsible for the scientific study of the theory, at some point the evidence of this theory has been reviewed. After that, some of the challenges raised against this theory have been studied. The major scientific challenges described in this chapter is based on recent advances made in biology, based on that, the mechanism of theory can’t explain the complex... 

Wilfrid Stalker Sellars (1912-1989) is an analytic philosopher whose philosophy is famous for being deep, systematic and extremely influential and notorious for being difficult to read. Although he has many original and interconnected ideas in different branches of philosophy- including metaphysics, epistemology, philosophy of mind, ethics, philosophy of language and meta-philosophy- the place of science in his system is completely indispensable. In his meta-philosophy, Sellars defines his philosophical project as an attempt to reconcile two distinct world-views of humanity in the modern word; scientific image and manifest image. Approaching Sellars’ philosophy by placing science at the...