Sharif Digital Repository

Inverse reinforcement learning (IRL) is one of the machine learning frameworks based on learning from humans; That is, instead of producing a decision process maximizing a predefined reward function, seeks to find the reward function based on the observed behavior of an agent. The biggest motivation of IRL is that, usually, determining a reward function for a problem is very difficult. We consider IRL in Markov decision processes; that is, the problem of extracting a reward function with the assumption of knowing the optimal behavior. IRL could be useful for apprenticeship learning to obtain skilled behavior, and for optimizing a reward function by a natural system. We first, determine a set... 

Networks of neurons produce diverse patterns of oscillations, arising from the net-work’s global properties, the propensity of individual neurons to oscillate, or a mixture of the two. Here we describe noisy limit cycles and quasi-cycles, two related mech-anisms underlying emergent oscillations in neuronal networks whose individual com- ponents, stochastic spiking neurons, do not themselves oscillate. Both mechanisms are shown to produce gamma band oscillations atthepopulation level while individualneu-rons fire at a rate much lower than the population frequency. Spike trains in a network undergoing noisy limit cycles display a preferred period which is not found in the case... 

Moving of living organisms appears in many interesting problems, e.g. the growth of bacteria colonies, tumor growth, wound healing, color patterns of animals and etc. There are many ways to model such problems and PDE theory is widely used to investigate these problems. In this thesis, we study two well-known classic models. First, macroscopic “Keller–Segel” model and then kinetic “Othmer–Dunbar–Alt” System. Since these models have a nice behavior in two dimensions that they don’t have in other dimensions, we propose a way to alter them such that they behave in this way in all dimensions. Also none of the known models have the suitable dynamics in one dimension, so our model has the property... 

Clustered Regularly Interspaced Short Palindromic Repeats, or in short, CRISPR is a relatively new technology that enables geneticists and medical researchers to edit parts of the genome by removing, adding, or altering parts of the DNA. Initially found in the genomes of prokaryotic organisms such as bacteria and archaea, this technology can cure many illnesses such as blindness and cancer. A significant issue for a practical application of CRISPR systems is accurately predicting the single guide RNA (sgRNA) on-target efficacy and off-target sensitivity. While some methods classify these designs, most algorithms are on separate data with different genes and cells. The lack of... 

Tipping points occur in diverse systems in various disciplines such as ecology, climate science, economy, sociology, and engineering. Critical thresholds in system parameters or state variables at which a tiny perturbation can lead to a qualitative change in the system exist in many subsystems in complex systems. These thresholds are called tipping points, and these subsystems are called tipping elements. Additionally, many systems with tipping points can be modeled as networks of coupled multistable subsystems. Domino-like tippings are called tipping cascades. Considering that these tipping cascades are primarily unprecedented, it is essential to study the dynamics and control of these... 

Thermal barrier coatings (TBCs) are used for increasing the efficiency and reducing pollutants of internal combustion engines (ICEs). In this paper, an optimization framework is developed in order to obtain the optimal dimensions for conventional coat, and the optimal dimensions and material property for functionally graded (FG) coat of a partially coated piston. A thermo mechanical analysis is investigated for Nano coat by finite element method. The conventional and Nano coats are made of MgZrO_3 as the insulating ceramic overlay and NiCrAl as the metallic bond-coat. The properties of the FG coat is assumed to vary according to power law through the thickness. For all tree conventional, FG... 

In this thesis, we present the results of a laboratory and numerical model study of the exchange flow generated by the temperature gradient between an open water heated by sunlight and a canopy area made of floating vegetation. Particle Image Velocimetry is employed to obtain the structures of the warm flow intruding the canopy at the surface and the bottom cold return flow for different roots length and vegetation density. Following an initial, transient stage of flow build-up governed by a balance between inertia and buoyancy forces, the flow reaches a steady state in the canopy area with a force balance between buoyancy and vegetation drag dominating the flow within roots. At the steady... 

In recent years, magnesium and its alloys have been considered as biodegradable implants, but they corrode in the body before natural process of damaged organs recovery is completed. In this investigation PEO operation was used for corrosion control and effect of different parameter such as number of operation steps, electrolyte type, time and operation voltage on coating properties was studied. Scanning electron microscopy was used for investigating of morphology of coats and to determine chemical composition and phase of coats EDS analysis and X-ray diffraction were used. The corrosion resistance of samples were evaluated by potentiodynamic polarization and electrochemical impedance (EIS)... 

During recent years a variety of decision making models for project selecting and priorities have been developed. Most of these models used quantitative indicators for projects evaluating and focused on financial and economic indicators. In this project, a decision support system for project portfolio management in construction industry has been developed. The most important feature of this model that distinct it from others is its relationship with the organization's strategies. On one hand, this model focuses on the organization to ensuring that the projects selected for investment, meet the portfolio strategy and on the other hand, it focuses on project management to delivering projects... 

In this study, the aging of the LiFePO4/graphite cell was investigated in two different types of 18650 Li-ion batteries during cycling at various C-rates (0.5, 1, 2, 3, 4C) and high temperature under long-term cycling. An amount of 20% Capacity loss was considered as the end of the cycling. Batteries with a capacity of 1500 mAh after this capacity drop, experience 60, 120, 1502, and 2155 cycles, at the rates of 4, 3, 2, and 1C , and batteries with capacity of 1400 mAh was also 60, 360, 1100, 1000, and 805 cycles at a rate of 0.5C. Capacity decrease of the cell is in linear relationship with cycle number and the slope of the capacity-fading line increases with elevating current rate. Aging...