Sharif Digital Repository

Early failure of pavement is one of the most important problems. As the research conclusions in Iran, Non-conformancity is the most important cause of this problem.Quality management system, Audits and expert systems are the solutions. This research provides an Audit system for quality management system of batch-type asphalt plants as the preliminary solution.A state survey conducted and useful part of state programs had been considered. After developing software, The system functionality has been tested  

Among the equipment used in supermarkets, refrigeration systems should be the focus of energy efficiency initiatives; Because they are the biggest consumers of energy and refrigerant with significant maintenance costs. Fault detection and diagnosis (FDD) can provide considerable potential for energy savings as well as reduced maintenance costs. Although there have been numerous investigations of FDD for HVAC systems, there has been very little research on the application of FDD for supermarket refrigeration systems. Therefore, this thesis focuses on the application of FDD to these systems and helps to fill these research gaps. The studied system is a commercial refrigerator system on a... 

Cloud Computing can be defined as a distributed set of virtual resources in order to be configured dynamically as an integrated system. One of the significant aspects of such systems is the method of task assignment which can affect the performance and efficiency of the whole system. The vast area of the size and complexity of the requests combined with the variable nature of the requested tasks, essence the use of the new smart strategies for the activity assignment. The main challenge of addressing non-functional requirements of the customers is in fact the software and/or hardware failures. The proposed failure-aware resource provisioning methods take into account failure probability... 

The aim of this study is numerical simulation of progerasive failure in conical structures that manufactured by tape-winding proceses in various temperatures. For this purpose, flat laminates by tape-winding proceses firstly manufactured using carbon/phenolic prepreg tape. Then tensile, compression, shear and thermal expansion coefficient specimens are cut from these laminates. Tensile and compression test are done on these specemens in fiber and matrix directions in temperature range 23-200℃ and stress-strain and stress-time curves are achavied. Using these curves tensile elastic modulus in fiber and matrix directions and Poisson's ratio are obtained in room temperature. Also tensile and... 

Prognostics is necessary to ensure the reliability and safety of lithium-ion batteries for hybrid electric vehicles or satellites. This process can be achieved by capacity estimation, which is a direct fading indicator for assessing the state of health of a battery. However, the capacity of a lithium-ion battery onboard is difficult to monitor. This paper presents a data-driven approach for capacity estimation. First, new features are extracted from cyclic charge/discharge cycles and used as health indicators. Three algorithms are used to characterize the relationship between extracted features and battery capacity. Decision tree, random forest and boosting algorithms are trained using a... 

Spin-Transfer Torque Magnetic RAM (STT-MRAM) is known as the most promising replacement for SRAM technology in cache memories. Despite its high-density, non-volatility, near-zero leakage power, and immunity to radiation-induced particle strikes as the major advantages, STT-MRAM-based cache memory suffers from high error rates mainly due to retention failure, read disturbance, and write failure. Despite its high-density, non-volatility, near-zero leakage power, and immunity to radiation as the major advantages, STT-MRAM suffers from high error rates. These errors, which are mainly retention failure, read disturbance, and write failure, are the major reliability challenge in STT-MRAM caches.... 

Considering input constraints is an essential task in the controller design. In this thesis, a controller has been designed for incommensurate fractional order nonlinear systems in the nonstrict feedback form subject to unknown dynamics, input nonlinearity and actuator failures. The Lyapunov direct method and the backstepping technique have been used to design the controller and stability analysis. The number of actuator faults can be infinite. In addition, the proposed control algorithm can cope with different types of input nonlinearities namely, saturation, dead zone, dead zone-saturation, backlash and hysteresis. To estimate the system uncertainties, neural networks have been employed... 

Structural Health Monitoring (SHM) is an effective method for the early detection of structural damage, and this method can reduce the maintenance costs of structures. In this thesis, the use of artificial one-way and multi-layer artificial neural network is evaluated to determine the damage to the structure. The neural network method used in this thesis is a post-propagation method. Finally, the numerically damage determine will be evaluated using a two-dimensional frame structure and a three-dimensional frame structure by finite element method. In this method, the dynamic properties of the structure are used only in the form of the modules. For this purpose, the finite element model is... 

The present research proposes a new method to establish a practical framework for extension of gas turbine life time. This method is based on an nine-step operational algorithm which is capable for different types of gas turbine. The essential inputs for this algorithm includes documents of inspection and knowledge of repair and maitenance experts. In this algorithm is used the Bayesian network probabilistic method. Therefore, based on the observations and the knowledge of experts, gas turbine Bayesian network is produced. According to this Bayesian network consequenses are created. Furthermore, making the steps of the algorithem more explicit, FTA and FMEA methods are used to creat the... 

This project is providing appropriate software which could manage maintenance activities in a plant. All sections of the software have been designed in a way that can ease the management of maintenance activities. There are about 100 forms in the software that have been designed according to the forms which are being used in some Iranian cement plants and other maintenance software and also what we recognized important to be added or designed. One of the most important aspect of this software is the analytical section of the software where the user can get analytical reports from the software and based on the reports judge about the status of the plant and make new decisions in order to... 

In this thesis, a novel probabilistic framework named Probabilistic Spectral Fatigue Analysis (PSFA) will be introduced for the purpose of assessing the performance of jacket offshore platforms under high-cyclic short-waves fatigue degradation. This method can take into account the uncertainties in three main elements consisting of material properties, sea state parameters and collapse capacity of structure. The main advantage of PSFA approach is the ability to recognize the fatigue failure scenarios and specifies the limit state function of critical members as a super-branch or sub-branch of those scenarios. Therefore, a new and accurate method is proposed for combination of scenarios’... 

The first project ,paid to review and analysis types of crack and agents Also, was referred methods to control them in rail industry .
The wheel of Alestom train and UIC60 rail were simulated and stress analysis by software FEM (ANSYS and ABAQUS) , and effect of various parameters such as applied forces , train wheel diameter , contact position and rail inclination on stress values was studied . For comparision of results has been used analytic Hertz theory .
By using experimental data on the subsurface crack , those cracks were created in the wheel . For load on the modeling wheel and rail, ,assuming contact on the wheel rolling point , were used vertical load of wagon weight ( with... 

Wall systems are an essential part of the buildings and their capacity should be properly considered in their design. However, the seismic behavior of building systems with in-filled walls and their interaction is a very complex issue, yet to be understood. Using the in-filled walls in the buildings without including them in the design process changes the whole behavior of the structural system as well as their failure mechanism under earthquake excitations. On the other hand, there have been extensive researches on rehabilitation of the structures with in-filled walls or designing them as the main or one of the lateral load carrying systems against seismic input. In this research, first the... 

Offshore wind energy is widely recognized as a renewable energy source that has the potential as a global energy source. Although the use of coastal wind turbines has been successful, it has been challenged in terms of visual, acoustic and environmental impacts. In addition, in terms of technology, it is difficult to achieve high levels of energy from coastal wind resources due to low annual average speed; Therefore, the wind energy industry is trying to make more use of the deep-water wind resources. However, before developing these types of deep-water turbines, economic challenges and technical problems must be resolved. Mooring failure is one of the major issues in the design of offshore... 

Wireless Sensor Networks (WSNs) are prone to faults due to battery depletion of nodes, where a node failure can disturb routing, as it plays a key role in transferring sensed data to the end users. A WSN may be partitioned into groups of nodes called clusters; for every cluster, there is a node, called Cluster Head (CH) that is responsible for collecting and transferring data from all nodes in that cluster. This means that the CH is a single point of failure; i.e., once a CH fails, the whole cluster will fail, which leads to inability of its members for transferring data outside the cluster. This thesis presents a Fault-Tolerant and Energy-Aware algorithm (FTEA), which prolongs the lifetime... 

In this study, through explaining a micromechanical model of progressive damage, failure in a composite conical structure under mechanical and thermal loads with 36 layers of carbon/phenolic material have been studied. To this end, first, mechanical behaviors of composite layers in micro and macro scale and their properties via fiber and matrix characterizations are discussed. In the following, selection of a proper RVE along with different types of boundary conditions on RVE are discussed. Then stress reinforcement coefficients in order to convert the mechanical and thermal stresses from macro to micro scale for carbon / phenolic material are extracted through defining appropriate RVE for... 

This document, is the thesis on the field of science and technology policy. The subject is the analysis and explanation of engineered innovation networks based on process approach and by using knowledge base concept. The failure of networks is one of the causes of the failure in the innovation systems, so the analysis of the phenomena would be very important for innovation policy makers for networking. The two main questions of this study are:
a) How do engineered innovation networks fail in the initiation stage?
b) How could we explain this process by using the concept of the knowledge base of innovative activities? During this study, which has beed done based on the... 

According to expanding penetration of Internet and the increased power of processing devices in the recent years, softwares are incisingly used for daily acitivies. The variety of hardware configuration and operating system of such devices leds the companies to take advantage of cross-platform software development methods. Although the production of cross platform software, resude development costs, it results in an specific type of faults known as platform-specific failures. These faults occur when software is running on specific platforms, and therefore, to identify and resolve them, the software test process should be performed on different platforms. To deal with this problem, we present... 

In order to improve the fatigue performance of torsion bar, induction surface hardening is performed. The aim of the present study is failure analysis of torsion bar and improvement of manufacturing process. Induction hardening was simulated using finite element method. As a result temperature history and residual stresses were obtained. Temperature and residual stress distributions are affected by the component geometry, the material behavior and the induction treatment parameters. Based on the residual stress distribution and the external fatigue loads, cracks can nucleate from the surface or below the hardened layer. Therefore, it is very important to determine the residual stress... 

In this investigation, the behavior of pin loaded composite plates is studied numerically. A failure prediction model is used to predict the ultimate strength considering three different mechanisms of failure: bearing, shearout and net tension. The model consists of two major parts: stress analysis and failure analysis. The main difference between this investigation and others is considering more realistic assumptions in modeling of the problem. As an example, we consider nonlinear behavior in the shear stress/ shear strain relationship of each unidirectional ply and use this model in optimization problem to reach maximum strength. The results are compared with experimental results available...