Sharif Digital Repository

Powder metallurgy is one of the most important and most usable methods in industries. Nowadays, many of the specimens are made this way. In this method, after powder compaction stage, because of sintering in high temperature, crystallographical structure of the material changes. This change results in poorer strength than initial powde. In order to avoid change and decrease in powder strength, shock consolidation is used. In this research, because of complication of this phenomenon and final quality of the specimen, shock consolidation of metal powders is investigated and analysed. This phenomenon is modeled, simulated, analysed and optimized mathematically.Various methods are used to create... 

The practice of river restoration has grown exponentially over the last several decades. There has been little empirical evaluation of whether restoration projects individually or cumulatively achieve the legally mandated goals of improving the structure and function of rivers. Nutrient reduction through simple methods is the most critical factor. The simplest method, which has minimal financial burden as well as preventing, and reducing the entrance of pollutants into the Chalus River (Mazandaran, in north of Iran), has been selected. The origins of rivers start at a high point and move with a steep. ... 

Vulnerability of water and sewage infrastructure in Kish Island survey versus natural and unnatural threats. It is important to know what to do when crisis or unpredicted event occurs in the Island. Decision makers and master managers of the Island, as the main custodians make suitable and effective reactions and decisions so that the impact of threats is reduced to minimum. According to the threats, there are short term and long term solutions. These solutions can be applied when the Island is encountered with crisis  

A major environmental challenge for wastewater treatment in Iran and other countries is the disposal of excess sludge produced during the biological process. This project has been developing and testing a technology that will help to overcome this challenge in Kish Island wastewater plant. Results demonstrate it can perform highly effective treatment of municipal wastewater while producing low levels of sludge.Applicationofvermifiltrationfor treatment of wastewater sludge using the Eiseniafetida earthworm species. The earthworms’ gut acted as a biofilter whereby there was reduction in the sewage wastewater’s solid and liquid organic and inorganic wastes through ingestion and expelling these... 

From the main factors causing an unpleasant odor can refer to indoles, askatels, mercaptans, some volatile organic compounds, sulfide hydrogen, ammonia, and the number of odor-causing compounds, which are also found in the wastewater facilities and sometimes produce unpleasant odors. Meanwhile, ammonia (Pungent and irritating odor) and sulfide hydrogen (colorless poisonous gas with the odor of rotten eggs) can be presented as major factors in sewage odor.
Several factors are involved in the foul-smelling hydrogen sulfide gas collection system and wastewater treatment. A few of them include numerous sewage pumping stations, selected the appropriate gradient in the collection system,... 

Nowadays, replacement of traditional cast iron shoes with composite brake blocks is a main project in railway systems. The main purpose of this replacement is noise reduction( for example by about 10dB for a 100km/h freight train). One of the main sources of noise emission is the rolling sound of the wheel on the rail. The rougher and more out-of-round wheel surface, the greater the noise produced. Cast iron brake shoes, still widely used on freight wagons, make the wheel surface much rougher than composite brake blocks due to the fusing of minute metal particles into the tread surface during braking. It is therefore necessary to replace the current cast iron brake shoe with a synthetic... 

Inflatable packers are a class of downhole equipments that are used for oilwell pluging operations. To set the packer inside the well, it is necessary to apply hydraulic pressure to it. By using the setting tool and installing an electropump in it, it is possible to transfer the fluid into the packer and supply the required pressure. In this research, an electropump has been designed and built that, firstly, is dimensionally suitable for the conditions of oil wells and, secondly, can have a good performance in the environmental conditions inside the well. This electropump, which can be used in a 2.125-inch setting tool, consists of a brushless direct current motor and a piston pump. To test... 

In the transportation industry, one of the most important and fundamental problems is the traffic of vehicles in the transportation roads. This problem is especially seen in large and densely populated cities such as Tehran. If traffic control is not done properly, it can lead to problems such as reduced traffic dynamics, environmental pollution, wasted drivers' time, disorder and loss of energy. If the traffic control is done after creating a traffic problem, it will not bring good results and will have low efficiency. For this reason, optimal traffic management and control has been raised as an important issue, especially in large cities. Predicting traffic flow is one of the important and... 

Inflatable packers have a great value in downhole operations due to their unique ability to expand to several times their initial diameter. These type of packers have a sealing element. This element is constructed of thin overlapped sheet metal ribs which are surrounding an inner tube. These overlapped ribs protect inner tube against the extrusion. The outer surface of this element covered by a layer of rubber. The outer elastomeric cover seals the annulus of the casing and isolates the zones in the well. In this study, some of the geometrical and material parameters effects on inflation and deflation of inflatable packers are investigated by numerical method. At first, for this purpose, the... 

Today, tens of millions of people on the planet suffer from heart disease. For the correct diagnosis and treatment of these diseases, there is a vital need for accurate scientific evidence such as various types of vascular and cardiac imaging. One of the applications of guidewires is in cardiovascular imaging. Of course, in addition to diagnosis, this device is also used in the treatment of disease. It should be noted that about 21 million central vessel catheters are performed annually on heart patients, of which about 16 million are performed using the seldinger method. Reportedly, unfortunately, 5% to 19% of these operations have had side effects and harm to the patient or failure.... 

Due to the relatively high freedom of selection of materials associated with a simple manufacturing method, a nonpneumatic tire (NPT) can be manufactured with low viscoelastic energy loss material. NPTs consisting of flexible spokes and the shear band are still at an early stage of research and development. An optimization study of NPTs’ geometry needs to be conducted, which is the objective of this thesis. Parametric studies and design of experiments (DOE) of an NPT are conducted with a hyper-viscoelastic finite element (FE) model to determine the effects of four design variables on rolling resistance, contact pressure and vertical deflection. Considering vehicle load carrying capacity and... 

Nowadays, water and energy shortage is the main concern of many industries. Every saving that could be done is valuable. In the first step of this project, energy recovery devices that are used in reverse osmosis systems, are reviewed and advantages and disadvantages of each system are investigated. These apparatuses save energy by recovering high-pressure energy from leaving brine and reduce the energy consumption of the device. The main focus of this study is energy consumption of the device that is used for desalination of seawater in reverse osmosis systems and on this basis, different energy recovery devices are compared. According to the investigation, results showed that most of the... 

Thread connections are widely used in tubular downhole equipment. Connections are usually weaker than tubulars and their failure will result in very high cost. Thread connections of downhole equipment are divided into two groups: standard connections and premium connections. Standard connections, despite being widely used, have limitations and will loose their efficiency in complex loadings. According to the mentioned limitations, premium connections have been proposed according to the existing need related to improving the strength of the structure, proper sealing and resistance to galling. One of the most obvious applications of premium connections is in downhole tubulars that are... 

Congenital heart defects are a type of heart diseases that some babies get at birth. These diseases generally have symptoms such as shortness of breath, headache, impaired blood supply, hyperplasia of the lungs, enlarged heart, and so on. In the past, open heart surgery was commonly used to treat such diseases, which was a costly and risky procedure. But over time, occluders made it easier. An occluder is referd to a device that is generally minimally invasive in the area of the fault and could block it. The occluders are usually braided type, with inside polyethylene fibers, where tissues can grow and clogs the defect over time. Although occluders have greatly increased the success rate of... 

Oil and gas extraction has long been considered one of the world’s major industries, with the economies of many countries, particularly Iran, heavily dependent on these resources. As the complexity of operations increases due to deeper wells and more challenging extraction conditions, we are witnessing continuous technological advancements in this field. Innovative tools are being designed and utilized daily to support and develop these industries. Downhole equipment typically has a cylindrical shape and must be positioned at specific depths to perform their respective functions. Obviously, these tools must withstand significant axial loads and weight, especially as drilling depth increases.... 

Shape memory alloys (SMA) exhibit a number of features which are not easily explained by equilibrium thermodynamics, including hysteresis in the phase transformation and ‘‘reverse’’ shape memory in the high symmetry phase. Processing can change these features: repeated cycling can ‘‘train’’ the reverse shape memory effect, while changing the amount of hysteresis and other functional properties. These effects are likely to be due to formations of localised defects and these can be studied by atomistic methods. Here we present a molecular dynamics simulation study of such behaviour employing a two-dimensional, binary Lennard–Jones model. Our atomistic model exhibits a symmetry breaking,... 

Nowadays, the lattice Boltzmann method has been widely used by scientists and engineers as an alternative to conventional numerical solvers for the Naiver-Stokes equations. The drag force decrease on the surfaces in industrial applications special in transport industries has always been of special importance. In the current research, the effects of the drag decrease has been investigated by making some rectangular grooves on the millimeter and micrometer scale on a flat surface that has been under external laminar flow of a single-phase fluid with the uniform type. Making grooves on the surfaces usually lead to change the contact area from the solid-fluid to fluid-fluid in the grooves area.... 

Shape Memory alloys are a kind of intelligent materials developed in recent years due to their comprehensive use in medical, robotics, and other advanced sciences. Two main characteristics of them are shape memory effect and superelasticity put these materials in the category of advanced materials. Recently, the new branch of them attracted many studies which is the porous shape memory alloys. The importance of this class of material is related to their properties such as bio-compatibility, superelasticity and shape memory effect. Since shape memory alloys are usually expensive, a new field is developed known as functionally graded porosity distribution. This method is performed by... 

One of the most important tools in industries such as oil, gas, mining and groundwater is inflatable packers. These tools are used for plugging and zonal isolation of a well. The most important member of this cylindrical tool is the elastomer, which is reinforced by metal wire ropes. These cables are placed at an angle relative to the axis of the cylinder and are wound in a helix shape. At both ends of the tool are rings that hold the cylinder. After running the tool into the well and placed in the desired position, by a pipe connected to it, fluid is pumped into it. This increases the diameter or inflation of the tool, and the outer skin of the elastomeric cylinder contacts the well and...