Sharif Digital Repository

Walking on legs using orthosis for spinal cord injury patients has many advantages and decreases the physiological and psychological problems comparing with wheelchair application, however high energy consumption and early exhaustion of patients are disadvantages of orthosis usage. The most important group of orthosis for spinal cord injury patients is RGO (Reciprocating Gait Orhtosis) which a reciprocating cable mechanism links two hip joints motion. So swinging of mobile leg gets easier and stability of patient in standing and walking step increases. Regarding to existent reports about high energy consumption in walking by orthosis, this project has been fulfilled to design an improved... 

Casing design is one of the most expensive parts in the drilling of oil wells, and any cost reduction with the basic design of these casing strings will significantly reduce the total cost of the operation. In recent years, occurring scenarios-based casing design has become popular; Because in many cases, it eliminates non-occurring scenarios such as gas kick and saves on drilling costs. In this study, we have tried to investigate all scenarios that may occur during the lifetime of the well, whether drilling or production, and for each well, based on its own field information, possible scenarios for each casing part are selected separately and the applying loads are calculated. For this... 

The concurrent flow of oil and water is a common occurrence in the field of multiphase flow in different fields including petroleum industry. In oil and gas, production engineers often face a situation in which more than one phase is flowing through the producers. In such conditions an accurate assessment of pressure loss inside the well plays a vital role in efficient and effective production planning. Changes in well orientation, wellbore diameter, reservoir and fluid properties as well as fluid flow rates are among parameters in which will affect the flow patterns that can occur inside a well during its life time. These flow patterns are created as a result of a competition between... 

Miniaturization of electronic devices with portable, flexible and wearable characteristics created a great demand for high-performance microscale energy storage devices with lightweight and flexible properties. Among the energy storage devices, wire-shaped micro-supercapacitors have recently received tremendous attention due to their small size, lightweght, and high flexibility. In the first part, the porous dendritic Ni-Cu film was prepared on Cu wire substrate (CW) for fabrication of high- performance wire-type micro-supercapacitors (micro-SCs). The porous structure with dendritic morphology provides a high surface area, short ion diffusion pathway and low contact resistance between... 

Noise pollution is one of the major issues in automative industry. Many of these noises are caused by the internal combustion engine. Using reactive mufflers in the car's exhaust path can effectively reduce this annoying noises. Imposed pressure drop caused by installation this mufflers must be within an acceptable range for the car engine. Resonators, despite having a much lower pressure drop than other components of the exhaust system, can be used to cover the weaknesses of the muffler in the acoustic performance of the noise reduction set. One of the most common methods for designing a resonator is to use perforated plates. In this study the effect of various geometric parameters of a... 

In this research, nanocomposite containing reduced graphene oxide nanosheets (RGO) and trimetallic three-dimensional (3D) Pt-Pd-Co porous nanostructures was fabricated by galvanic replacement technique. First, GO suspension was drop-casted on the electrode surface, then GO film reduction was carried out by cycling the potential in negative direction to form the RGO on GCE (RGO/GCE). Then, electrodeposition of the cobalt nanoparticles (CoNPs) as sacrificial seeds was performed onto the RGO/GCE by using cyclic voltammetry. Afterward, Pt-Pd-Co 3D porous nanostructures fabrication occurs through galvanic replacement method based on a spontaneous redox process between CoNPs and solution... 

Throughout recent decades, one of the most important and challenging problems in robotics has been robot's path planning. Path planning means a robot must find its way from start to the goal point and track it without any collision to the obstacles. For this aim during the recent decades a wide variety of algorithms such as A*, Dijkstra and … have been proposed that some of which generate an optimal path as their output while others tend to create only a path regardless of its optimality. One of the most practical path planning methods is RRT algorithm which is executable in real-world applications, and by generating some nodes randomly then creating a tree-based graph, thereby outputting a... 

Nowadays, the assembly process is planned by an expert and requires knowledge and it is time-consuming. The flexibility and optimality of the assembly plan depend on the knowledge and creativity of the expert, and therefore expertise is an important parameter in developing the assembly plan. Therefore, the use of intelligent methods to plan the assembly process has been considered by many researchers. . The reinforcing learning approach has the potential to solve complex problems due to the use of experience gained from interacting with the environment and Has been successfully implemented in controlling many robotic tasks. However, due to the inherent complexity of the assembly, as well as... 

In the current status of the world production business, any action that can improve quality or decrease the price of products is very important to manufactures. Therefore, many studies had been conducted to do this. In production stages, the assembly stage includes 30% of production cost and up to 40% of production time. Therefore, optimization and design of the Production sequence of this stage are very important. This matter is more important in complicated and multi-segmental productions such as car manufacturing, the Aviation industry, and the shipbuilding industry. Also, optimization of the Production sequence could improve product quality. In this study, an algorithm has been purposed... 

A novel amperometric non-enzymatic glucose (NEG) sensor is designed by a facile preparation method. It is made by electrodeposition of Cu clusters and converting them to Cu(OH)2 nanotubes (Cu(OH)2NTs) arrays along with thin-film electro-polymerized of spindle-shaped polypyrrole (PPy@Cu(OH)2NTs), which have been doped by using sodium Benzene-1,3- disulfonate as an anion dopant. The electrochemical performance of the modified electrode toward glucose detection is investigated by various electrochemical methods. Under the optimized conditions, a significant electrochemical response improvement is observed toward the electro-oxidation of glucose on the surface of PPy@Cu(OH)2NTs electrode... 

In this thesis we investigate different factors of graphs with emphasis of even and odd factors. First, we prove the best existing lower bound for the largest even factor of graphs which is of the size at least 4/7|E(G)|+1 and we show that this bound is tight and classify the graphs which exactly meet this bound[]. Then we present a new lower bound for the largest odd-factor of graphs of even order which is of the size at least 2/5|E(G)|. We prove this bound using a new edge coloring called 1/2-coloring in which edges are colored with blue and red such that in each cycle the number of red edges is bigger than the number of blue ones. We prove in every 1/2-coloring of graphs with δ(G)≥3 or... 

In the first part, Co-Zn hydroxides were deposited onto CuO nanorods, and their electrochemical behavior and capacitive performance were investigated. To this end, Cu(OH)2 nanorods were grown on copper foam through a chemical process. Then, Cu(OH)2 were converted to CuO nanorods via a calcination process. In the next step, Co-Zn-OH sheets were electrodeposited on CuO nanorods. FE-SEM images of the prepared electrodes demonstrate the formation of Co-Zn-OH nanosheets onto CuO nanorods. Crucial electrochemical evaluations such as cyclic voltammetry (CV), galvanostatic charge/discharge (GCD), rate capability, and electrochemical impedance spectroscopy (EIS) were carried out. According to the... 

The main responsibility of a primary cement job is to provide hydraulic isolation between various zones. Cement-sheath evaluation is concerned with the question of whether zonal isolation exists. Cement Evaluation Logs are used to evaluate the quality of cement sheath behind the casing or liner after cement job. these logs are a part of well integrity logs. Cement Evaluation Log results are complex and can be misunderstood, and it can lead to bad decisions that could have severe consequences. Cement evaluation logs must therefore be interpreted by experienced professionals. To help these interpreters, we propose a system for automatically interpreting cement evaluation logs, which they can... 

Underbalanced drilling is a type of drilling operation in which the pressure of the drilling fluid is less than the pressure of the formation. This pressure difference has created advantages for this method. Less formation damage, reduction of pipe stuck, increasing rate of penetration and production during drilling are the advantages of this method compared to traditional methods. To reduce the pressure of the drilling fluid, very low density fluids should be used. One way to reduce density is to mix a compressible fluid such as gas into water. Due to the difference in density and surface tensile strength of water and gas, these two phases do not combine, so a stable combination of these... 

Improving the performance of compressors plays a key role in saving energy in industries. The presence of aleatory and epistemic uncertainties, such as dimensional, geometrical and environmental uncertainties, causes the tolerances that are within the allowed ranges in normal assembly conditions to violate the assembly requirements in operational conditions and cause a drop in compressor efficiency. In order to reach the dimensional and geometrical tolerances of the components of a compressor, especially in the design of the rotor and stator blades, that guarantees the optimal and stable performance while not increasi the production costs, there is a need for an optimal and robust tolerance... 

The reduction of the effective permeability of the reservoir rock in the production area due to various factors is called formation damage. Formation damage is always one of the topics discussed in petroleum engineering. Among the primary and important cases that lead to damage to the formation are the filtration of drilling mud into the production area and the deposition of colloidal particles inside the porous rock during the drilling operation. The length of the productive zone in contact with the drilling fluid usually reaches several hundred feet in Iranian formations. In this study, the aim is to more accurately estimate the amount of permeability reduction caused by the penetration of... 

Additive manufacturing (AM)has gained extensive industrial and research attention in recent years. Reducing manufacturing waste, lead-time and costs and the ability to build surfaces and parts with complex shapes, assemblies all at once or parts with internal features are some benefits of AM. However, complex error generation mechanisms underlying AM digital physical chains are likely to result in geometrical inaccuracies of the final product, thus posing significant challenges to design and tolerancing for AM. Therefore, predictive modeling of shape deviations is critical for AM. With increasing volumes and varieties of data, machine learning has gained extraordinary popularity due to its...