Sharif Digital Repository

Crack detection is a critical task in monitoring and inspection of civil engineering structures. This study proposes a deep-learning-based model for automatic crack detection on the concrete surface. The proposed model is an encoder-decoder model which uses EfficientNetB7, the state-of-the-art convolutional neural network, as encoder and the U Net’s expansion path as decoder. To minimize the training time and maximizing the accuracy, we use transfer learning in our approach. We train our model with a novel training strategy on images from an open-source dataset and achieve 96.44% F1-score for unseen test data. To compare the performance of the proposed method, we evaluate our model on CFD... 

Recently, there has been a surge of research activities in the area of networks in the systems and control community. One foundational class of questions on networked systems pertains to their controllability. While there are classical tests to check the controllability of linear time-invariant (LTI) systems, their applications to large-scale networks is numerically infeasible. Indeed, finding a minimum cardinality set of input nodes that ensure the controllability of a network is NP-hard. Moreover, when the interaction strengths along the edges of a network are unknown, the classical controllability test cannot be applied. To overcome these issues, an alternative set of approaches involves... 

Due to recent advances in laser technology and instruments, laser assisted machining processes has gained extra attention by scientists and industries. Naturally, effective modeling of the process is of great interest for researchers. Machining processes are generally modeled via FE tools and based on the requirements of model, it can be performed either mechanically or thermos-mechanically. About the LAM problems, it is basically meaningless to have a model without considering thermal effects. Hence, modeling is performed in two steps where through the first one, a thermal problem is solved to bring the temperature distribution of the work piece as the initial conditions of the next step.... 

In this thesis, optimal offering strategy problem of a virtual power plant (VPP) as a price-maker player in day-ahead frequency constrained electricity market is presented. The optimal offering strategy problem is modeled as a bi-level optimization problem. In the upper level, the total profit of VPP is maximized. In the lower level, the clearing conditions of frequency constrained electricity market is modeled. The proposed bi-level optimization problem is reformulated as a mathematical programming with equilibrium constraints (MPEC) problem by using Karush-Kuhn-Tucker (KKT) conditions. Then, the proposed MPEC problem, which is nonlinear and hard to solve by commercial solvers, is... 

This reaserch is study on the performance of evaporation tubes used in mini jet engines which has been done experimentally using laboratory equipment. In this study, researchers have tried to simulate the laboratory conditions as much as possible to the real conditions inside the mini-jet engine, increase the accuracy of the results and increase the results and bring them closer to the results inside the mini-jet engine. The experiments are divided into two categories, cold and hot In cold tests, an attempt is made to study and investigate the types of two-phase flow regimes created by applying different fluid and air flow rates, and to select annular flow regimes from among them.... 

Growth of the fuel consumption in the world and the greenhouse effect of its pollution get industrial managers and environmental activities attention. Skin drag force has a significant role in energy uses. The drag reduction property of superhydrophobic surfaces shows a new approach for investigators to reduce energy uses. Surface with 150° contact angle called superhydrophobic surface.In this project, a superhydrophobic coating is developed based on acrylic hydroxyl resin by silica nanoparticles. This coating can be sprayed on any surface. Using the Iron oxid particles and silica nanoparticles together produces hierarchical micro-nano structures. This coating has a 160.1° contact angle on... 

One of the natural functions of wetlands is to neutralize the dangers caused by floods. Therefore, if a facility is built in the area of wetlands, it should not disturb their natural functioning. During the Iran-Iraq war, several antenna roads were built across the wetland, and the construction of these roads divided the wetland into 5 separate reservoirs. After the end of the war and with the development of the oil fields west of Karun (Hor al-Azim region), the extraction of oil from this region was put on the agenda. With the flood of April 2018, these facilities and roads were exposed to damage and flooding, and oil production from these reservoirs was stopped. In this research, after... 

Over the past five decades, the proliferation of electronic devices and the advent of Internet of Things (IoT) technology have ushered in a profound revolution in integrated circuit technology. In contemporary electronics, digital integrated circuits rely predominantly on CMOS transistors. Among the notable limitations associated with CMOS transistors are their non-zero off-state current and limited sub-threshold slope. In response to these limitations, researchers have ventured into a burgeoning field known as "Beyond CMOS," exploring technologies like Tunnel Junctions, Carbon Nanotube FETs, and more. Additionally, alternative approaches that blend electronic and mechanical principles in... 

Price limits are boundaries established by market regulators to confine daily movements of security prices within a predetermined price range. In this study, we have used the data of trades of all companies listed in the Tehran Stock Exchange during the years 1385-1393 to study the characteristics of stocks that hit price limits repeatedly using a panel regression model with fixed effects and the generalized method of moments (GMM). In fact, this study aims at investigating the price limits in Tehran Stock Exchange by a novel and distinct approach. In general, risky stocks exhibit more price volatility and thus are more likely to experience price-limit hits. In summary, the results reveal... 

In this project, bioleaching has been investigated as a solution for detoxification and metal recovery of spent hydrocracking catalysts of Tehran petroleum refinery which is listed as a hazardous waste. In this project four stages has been accomplished as follows: 1- Adaptation of Penicillium simplicissimum and Aspergillus niger with different heavy metals present in a spent hydrocracking catalyst, individually and with mixture of metals as well as adaptation by spent catalyst which the cumulative action of multi-metals enhanced the toxic effect; 2- The one-step, two-step, and spent medium bioleaching of the spent catalyst by the adapted fungi in batch cultures were investigated and... 

Most of the real-world systems can be modeled as closed loop systems which are made up of a LTI subsystem in the forward path and a memoryless nonlinear subsystem in the feedback path. Such systems are called “Lur’e systems”, the name of the first who introduced these systems. Because of the generality and the wide applicability of this type of systems, studying the stability of them has been notable and interesting to many scientists for a long time. Meanwhile, in recent decades, many scientists in physics and engineering sciences have been interested in applications of the fractional order systems and as a result focused on studying the features of the fractional order systems. An... 

The aim of this project is to achieve a semi permeable high flux membrane with a reasonable salt rejection for the treatment of low osmotic pressure water. A thin film composite membrane consists of three polymeric layers was studied in this project. These layers were polyester support, polysulfone sub layer and polyamine selective layer. The polyester support provides the mechanical resistance against the operating pressure. The polysulfone sub layer provides the suitable area for polyamide synthesize, and the polyamide layer is the selective active layer of membrane.
The resistance to water penetration in sub layer was reduced first and then, the pores in the polyamide layer refined by... 

In this project, cellulose acetate butyrate (CAB) nanofibrous membranes in order to separate the contaminants of an industrial wastewater were prepared. Electrospinning process that is an effective method to fabricate nanofibers was used to prepare the membranes. Since various parameters affect this process and fibers morphology, optimization of these parameters is necessary for preparation of improved membranes. So the effect of parameters of solvent system, polymer concentration, applied voltage, distance between the tip of needle and collector, and rotational speed of collector on morphology and diameter of the nanofibers was investigated. Scanning electron microscopy (SEM) and image... 

Pose and motion estimation using a set of images is a common application in photogrammetry and one of the most popular methods in doing so is Bundle adjustment. This method later got adapted to the field of computer vision and is mainly used to reconstruct a 3d scene while also estimating pose and motion of the camera. There are a variety of other methods used to estimate pose and motion. Most non-visual methods like using inertial navigation system and GPS suffer from shortcomings like accumulative error, availability problems or low accuracy. While most vision based one are computationally expensive. In this thesis two methods are proposed to increase accuracy and efficiency of one variant... 

In the recent years, the world has been faced with a spectacular increase in variety and usage of electronic and electric devices. Unfortunately, the highly increasing march of technology reduces the time of their usage, causing a high degree of electric and electronic waste. Nonetheless, these E-waste enjoys a high percentage in precious metals such as Cadmium, Copper, Nickle, Zinc, Barium, Beryllium, Aluminum, Gold, Silver, Platinum, and so forth. With this in mind, they can be named as “secondary mines”, enjoying higher in degree of these metals even than natural mines. Therefore, extraction and recovery of the very metals are of great importance. Nowadays, using microorganisms in order... 

This research aims to expand comprehensive information about bioleaching of different kinds of electronic waste (E-waste). The selected wastes were computer PCBs (CPCBs), mobile phone PCBs (MPPCBs), television PCBs (TVPCBs), fax machine PCBs (FPCBs), copy machine PCBs (COPCBs) and central processing units (CPUs). At the first step, a comprehensive study made on the E-waste structure. The best method for precious metal digestion analysis introduced, i.e., using aqua regia, hydrogen peroxide, hydrofluoric acid, and boric acid. The economic values of the E-wastes were as follows: CPU> MPPCBs> COPCBs> FPCBs> CPCBs> TVPCBs. Among the metals, gold attributed to the highest value distribution and... 

A geometric network on a set V of points in d-dimensional Euclidean space is a weighted undirected graph G(V,E) with vertex set V such that the weight of an edge is the Euclidean distance between its endpoints. We say that the geometric network G(V,E) is a t-spanner of V, for a t > 1, if for each pair of points u and v in V there exists a path in G between u and v of length at most t times the Euclidean distance between u and v. In this thesis, we introduce the new concept of local t-spanners and present some algorithms to construct these geometric graphs. Suppose Gc(V ) is a complete graph and F is a family of convex regions, for instance set of half planes, squares and circles. The graph... 

Performance of reinforced concrete frames is highly dependent on detailing of the joint connections between its members, such as beams and columns. To have a good structural behavior, joints must show ductile behavior and designed based on the philosophy of strong column-weak beam. In the case of sever lacking ductility, strength or even rigidity of the connections, or having a weak column-strong beam, in the existing structures, there is a need for seismic upgrading of the connection. There are several ways for seismic upgrading of this type of connections.In this research, using steel plates for seismic upgrading of Concrete Beam-Column connections subjected to axial and cyclic loads has... 

In this thesis designing of analog integrated circuits of contactless smart card in 0.18 um CMOS technology has been done according to the defined specifications in the related standard. This design includes two main parts which consist of power supplying blocks and data extracting blocks. Also for designing and simulating analog section circuits a suitable model of wireless interface between card and reader is needed which is obtained by some measurements on a specific card and reader. Power supplying blocks consist ofrectifier, regulator and the reference voltage and current generator circuits. Decreasing power consumption and increasing the power efficiency factor is considered in... 

Every year, an enormous amount of catalysts are consumed in oil refineries during refining processes. After some regeneration cycles in order to recover their activity, they are not anymore effective and must be disposed. These spent catalysts are regarded as dangerous solid wastes as they significantly include some contaminations like vanadium, nickel, arsenic, sodium. From another point of view, the metals present in spent catalysts are highly valuable and are used extensively in steel industry and manufacture of special alloys. So, it sounds profitable to extract and recover these metals from such a cheap source instead of minerals and ores. Basically, there are two main processes, hydro-...