Sharif Digital Repository

Casing collapse is a long-standing problem in Kopal oil field, located at a distance of 60 km of east of Ahwaz, Iran. In this field, so far casing collapse has encountered in 18 well-bore out of the 56 drilled-well-bore (~32%) due to creep loading caused by salt flow, which resulted in tremendous economic loss. Among all the different set of factors leading to such a problem, the effects of the local stress distribution on the wellbore wall and casing (resulted from the in-situ stresses, and stress perturbation due to drilling), pore pressure, the casing quality and material, and the applied-cement type are important. In order to investigate these factors and their effects, they should be... 

Additive manufacturing (AM) has gained significant attention in recent years as a novel approach to fabricate three-dimensional parts. Its advantages, including high speed, low-cost production for small-scale batches, and greater design freedom, have made it a competitive alternative to traditional manufacturing methods. However, the application of AM for components subjected to fretting fatigue requires careful evaluation. Fretting fatigue is a major cause of failure in turbines, particularly at the contact interface between turbine blade roots and disk. In this study, the influence of AM and post-processing treatments on the fretting fatigue life of Ti-6Al-4V alloy was investigated. Five... 

Recent advances in WSN have led to next generation of it for multimedia transmission which is WMSN. WMSN has several applications like environmental monitoring, advance health care delivery and etc. However, providing QoS requirements of transmitting video data like delay, bandwidth and packet loss with minimum distortion at perceived video quality over WMSN with resource constraints is a challenging problem. Using multipath routing protocol for video communication can increase bandwidth and decrease delay over WMSN. Moreover, all video packets have not the same effect on video distortion. We propose a scheduling mechanism which classifies packets according to their types and contents and... 

Precipitation in the water year 1396-1397 is the lowest in the past decade. The present study is conducted during this water year and focuses on the effects of climate variables such as temperature and precipitation on child labor supply between Tir 1397 and Farvardin 1398. Children and household characteristics are also taken into account when evaluating child labor supply using OLS and Logit methods. Estimation results indicate that both child work hours and participation in the job market decline with an increase in precipitation. Furthermore, how much time children spend working or studying is heavily influenced by parents' income. The temperature variable does not have a significant... 

Existing face forgery detection methods mainly focus on certain features of images, such as features related to image noise, local textures or frequency statistics of images for forgery detection. This makes the extracted representations and the final decision depend on the data in the database and makes it difficult to detect forgery with unknown manipulation methods. Solving this challenge, which is called the generalization challenge in artificial intelligence literature, has become the main goal of researchers in this field. In this thesis, the focus is on extracting effective features for success in forgery detection and preventing the performance of the forgery detection network from... 

One of the most important problems in machine learning is investigating the performance of the learning algorithms, and especially deep neural networks, on adversarial examples, which are generated by imperceptibly perturbing input images, so that cause the model make a wrong prediction. Not only this line of research is important for making deep neural networks dependable, but also can help with understanding the fundamental limitations of deep neural networks, and the nature of their operation, which can in turn provide researchers with valuable insights into artificial intelligence. In this research work, we have tried to approach the topic with a mainly theoretical mindset. The method we... 

In this work, a comprehensive survey on the different methods of modeling fluidized beds was done. Finally, the discrete particle method with soft particle approach was selected as the method of modeling the solid phase. For the gas phase, computational fluid dynamics (CFD) as the method of modeling is used. In order to verify our simulation results for the solid phase, a simulation of a bed with many particles distributed all around the bed was done. At the first second of the simulation, the gas phase flow was truned off and the particles were falling down. The results obtained with this method were verified with the references. For verification of the gas phase, a 2D bed with the gas... 

The Onsager's conjecture is concerned with the dichotomy between rigidity and flexibility of weak solutions of incompressible Euler equations. Lars Onsager conjectured that weak solutions of Euler equations that are not smooth enough could be dissipative, even without the help of viscosity. On the other hand, it is well known that $C^1$ solutions conserve energy. Onsager conjectured that C^(1/3) regularity marks the threshold for this dichotomy. In other words, Hölder continuous solutions with Hölder exponent greater than 1/3 conserve the energy, while for every Hölder exponent less than 1/3, there are dissipative Hölder continuous solutions. The threshold 1/3 is intimately tied with... 

Sustainable transportation is a system that allows the basic access needs of individuals and societies to be met safely and in a manner consistent with human and ecosystem health, and is affordable with equity within and between generations. The current research of sustainable transportation uses environmental, economic, social and transportation variables of various world cities. The study database was developed based on global urban transportation databases covering numerous cities for 4 decades for period of 1960 to 2001, Furthermore 3 decades of pertinent variables for Iranian cities of Isfahan, Tehran and Mashhad. Firstly sustainable transportation indicators were developed by reviewing... 

In recent years, the demands come to data centers have increased significantly, so huge amount of energy consumption, cost of this usage and environmental effects of data centers have become serious issues. Accordingly using solar energy to provide some portion of a data center’s energy usage can reduce environmental effects efficiently. Also smarter use of this energy could decrease overall cost of energy in data center. The demands that come to a data center are categorized to critical and non-critical workloads. Running of Non-critical workload (batch job) can be moved to another time according to its deadline. This work suggests a solution that schedules batch jobs considering solar...