Sharif Digital Repository

Analog computing has emerged as a promising candidate for Neural networks' implementation due to its high Interconnectivity, high bandwidth, parallel computing, high-speed processing, and low power consumption. Artificial Neural Networks have a wide range of applications; however, the Implementation of complicated Neural Networks on traditional computers would encounter two fundamental obstacles: limited processing speed and non-optimal energy consumption. This thesis's primary focus is on designing and simulating a whole-passive planar Optical neural network(ONN) based on silicon photonics technology. Firstly, the concept of ONN is studied using some lately proposed work. The device is... 

Path planning is essential for unmanned aerial vehicles (UAVs) to navigate complex and hazardous environments. Many algorithms have been proposed to solve this problem, but heuristic, meta-heuristic, and hybrid algorithms have recently gained attention due to their ability to find approximate solutions quickly. In this thesis, we propose using the Late Acceptance Hill Climbing (LAHC) algorithm for UAV path planning. We compare LAHC's performance to classical and state-of-the-art optimization algorithms, including simulated annealing (SA), grey wolf optimization (GWO), symbiotic organisms search (SOS), and simplified grey wolf optimizer-modified symbiotic organisms search (SGWO-MSOS).... 

With the increasing development of Internet of Things (IoT) devices, issues such as establishing effective communication, optimizing energy consumption, ensuring reliability and improving the quality of services provided by these devices become more and more complex and critical challenges. With the introduction of fog computing model by Cisco in 2012, some of these challenges were successfully managed. Fog computing is a distributed computing paradigm that acts as a middle layer between cloud data centers and IoT-based devices/sensors. By distributing computing resources closer to edge devices, fog computing enables real-time data processing and analysis. However, one of the key aspects in... 

In recent years, thin-film photovoltaic cells with thicknesses of less than 1-2 µm have been developed with potentially lower production costs. Due to the small thickness of the absorbing semiconductor in these cells, the absorption is inevitably low at energies close to the electronic band gap of the semiconductor. This is particularly a problem for thin-film devices. Recently، periodic metallic nanostructures supporting surface plasmons have been introduced as alternative solutions to achieve light trapping in thin-film solar cells.Full numerical methods are usually used for the analysis of these periodic structures. The main drawback of these methods is that they are time-consuming and... 

Dams are one of the vital infrastructures of the country and their correct use can have a significant impact on reducing costs and increasing their productivity. Due to the fact that dams are mainly large structures with a large number of components and with many complications of operation and maintenance, their operation and maintenance require spending a lot of money. On the other hand, the depth and volume of water behind the dams and the entanglement of the connection between the dams and the surrounding environment make the operation and maintenance of dams face many risks. The use of new technologies that can reduce the costs and risks of operating and maintaining dams can greatly help... 

Iran is a developing country where construction activities are significantly increased annually. Construction project contracts have a crucial effect on the project ensuring implementation that carries out the expectations and requirements of all parties. Additionally, building construction is a cost and time-consuming process. Builders and construction contractors must adhere to balanced contractual norms and standards to reduce the costs incurred by the contracting parties and to appropriately respond to the risks occurred. The next significant concern is reducing contractual claims and disputes that can delay the project's operation for an extended period. The necessity of preparing a... 

Most of the robust or optimal controllers can produce extremely fragile controllers [1], in the sense that vanishingly small perturbations of the coefficients of the designed controller destabilize the closed-loop control system. Modern control methods, including robust control, lead to high order controllers.Often times a reduced order controller is implemented. As a result, need for low order control design reducing controller’s ensitivity is tangible. Based on studies carried out, properties of normal matrices can be employed to define a fragility measure. In this thesis, a new convex criterion measuring controller fragility is defined. Then, a more resilient reduced order controller can... 

In modern cryptography the main goal in symmetric cryptography algorithms is that the security of the protocol should be only dependent on the secrecy of key. Further, secret key agreement has a major role in perfect security. However, it is impossible to share a secrete key only by the use of a public channel and there must be another shared source. This source can be for instance random variables with some joint distribution (as in source model classical key distillation problem) or it can be some entangled quantum systems (as in quantum key distillation problem). The question here is that with the optimum efficiency, what is the maximum number of key bits that can be distilled from one... 

The high consumption of worldwide fossil energy and its detrimental effects on the environment and climate have prompted a transition toward renewable energy sources. The availability of renewable energy sources depends on weather and seasonal changes; therefore, an imbalance between supply and demand would be unavoidable. Hydrogen storage as an energy carrier, can fulfill this energy mismatch. Storing hydrogen in underground formations, such as aquifers, has been the subject of extensive research recently. In these storage reservoirs, hydrogen contacts the resident brine which will be lost through the dissolution-diffusion mechanism. Therefore, successful design of these storages requires... 

Nowadays, the construction industry has undergone extensive changes, with the advent of new technologies, it has departed from the traditional project implementation methods. One of these technologies is Virtual Reality, which is becoming more widespread in various stages of the life cycle of a project from design to delivery. Providing an opportunity for people to see the details of the final construction before completing the project could be regarded as one of the capabilities of this technology. Also, evaluating the project’s features at the time of construction and having a close understanding of product’s reality are the other beneficial aspects of VR. Meanwhile, the emergence and... 

In several electro-optic and optoelectronic devices, we require the structures with simultaneous high electrical conductivity and optical transparency so as to transmit the incident light. Transparent Conductive Electrodes (TCEs) that are both highly conductive and transparent were introduced to be an answer to the mentioned challenge. Periodic arrays of metallic holes are amongst the most important structures that are used as transparent electrodes. Using the metals with low electrical resistivity, such as Au and Ag, provides these structures with high electrical conductance. On the other hand, since these micro/nano structures support the propagation of guided electromagnetic waves, light... 

The need for a fast, light and affordable payment method, was a reason to produce multiple payment channel network on various of networks. To deploy and expand these networks, we need to deploy a profit model for new customers on the betweenness they add to network. In this research we maximum profit solutions for network with fixed payment cost and network with reduced betweenness profit for longer distances.At first, we suggest for a limited fund, we decide to make channels with most betweenness profit and prove it's a np-hard problem. Then for limited charge of making new channels, we show that it's a np-hard too. In graph of a path, we prove there is a solution based on length of path,... 

In its most general form, analysis of macroscopic electromagnetic behaviour of a medium must include the dependence of magnetic flux density on the electric field and electric flux density on the magnetic filed. This new degree of freedom can lead to new propagation phenomena and result in novel microwave and optical devices. In recent years, numerous theoritical and exprimental studies have been carried out to fabricate these bi-anisotropic materials and understand their behaviour. A particular class of bi-anisotropic materials is electromagnetically equivalent to an anisotropic medium with gyrotropic permittivity and permeability tensors that operate on pseudo-electromagnetic fields. In... 

Order reduction is a very important issue in Control Theory. A growing need for order reduction models in different fields such as simulation, identification, and design of control system shows this significance. Actually, a high-order system makes a great deal of complexity in designing hardware of control system, debugging, and implementation. Till nowadays, many repetitive as well as nonrepetitive methods with various criteria have been introduced to find low-order models. In this research, order reduction of linear time invariant system models is analyzed. The selected criterion for measuring error between original system and reduced order system is the norm of H1 because it is not only... 

One of the most significant factors for the on-time and successful implementation of construction projects is contract management. Proper management of construction contracts and assessment of potential risks in the bidding process and before its signing have a significant impact on preventing or reducing the occurrence of claims and disputes between the contract parties at various stages of the project. In this research, using the latest deep learning (DL) and natural language processing (NLP) state-of-the-art methods, and various deep neural networks (DNN) architectures a model has been developed for extracting Persian contract risk-prone clauses. In addition, this study provides a... 

Today, with the popularity of online shopping, many business owners are interested in launching online stores. Recording opinions and using the opinions of customers and buyers of products provides the possibility of listening to the opinions of customers in the design and improvement of products. On the other hand, other users and those who intend to buy a specific product, after paying attention to the features and aspects of the product they want, refer to the section of customer views and opinions. The user also reads these comments among thousands of different sentences and words written with different opinions and suggests; It gets confusing and many users won't be able to make the... 

Frequency synthesizers are one of the most critical building blocks of RF systems. Their task is to produce high-frequency precise and stable clock signals from a low-frequency source. The signal used in mixers to up-convert and down-convert desired signals in transceivers and the precise clock of analog to digital converters are made by frequency synthesizers. Designing frequency synthesizer, because of its lots of parameter and dependency of these parameters to each other, is a hard task which forces designers to propose new structures. In this thesis, an integer-N frequency synthesizer for Bluetooth application, with the goals of decreasing spurious tones power and settling time, is... 

Studying the statistical dependence of two or several random variables is the basis of statistical estimation and prediction. The correlation measures such as mutual information, Pearson correlation, and maximal correlation are common tools in quantifying the extent to which two random variables are dependent. While such measures are highly informative and computationally simple for jointly Gaussian random variables, it is not the case for general random variables. Infinitely divisible random variables are typical examples that are characterized in the Fourier domain (characteristic functions are known); except for a few special cases, no closed-form expressions are available for the... 

Energy and water are valuable resources that underpin human prosperity and are to a large extent, interdependent. Water is used in multiple phases of energy production and electricity generation, from fossil-fuel extraction, transport and processing,irrigating crops for biofuels, to providing cooling water for thermoelectric power plants. On the other hand, all such processes, alongside with other industrial and municipal water uses, require sufficient energy required to extract, treat, and deliver water.The key objective of this project is to maximize both water and energy economic potentials while considering the environmental impacts associated with their consumption. In this regard,... 

Digital computers, comprising universal logic gates, are tremendously versatile. This versatility associated with the increasing integrability of digital electronics due to Moore’s law has left nearly no room for analog computers in the last few decades. However, in the case of some specific problems such as modeling complex and nonlinear systems or pro-cessing large amounts of data, computation time and power is still a serious restriction of digital computing. Optical phenomena are fast enough and offer novel approaches to overcome the mentioned restrictions about the system speed and power consumption. Therefore, optical structures make possible to perform ultra-fast spatial analog...