Sharif Digital Repository

Today, the additive manufacturing process is one of the most important manufacturing processes. In the additive manufacturing process, the mass of the parts is directly related to the printing duration, in addition to the costs of consumables. On the other hand, the use of lighter parts in industries, such as the aviation, is one of the important requirements of those industries, and topology optimization is needed to reduce the consumables and the mass of the parts. Also, since in the optimal design of engineering parts, more than one design objective is usually considered, the multi-objective optimization of topology is of great importance. The Moving Morphable Components is one of the new... 

Researchers have paid more attention to greenhouse cultivation, due to the exacerbation of food and water crisis. Higher production with lower cost could be achieved through greenhouse climate control (temperature, humidity, carbon dioxide concentration). However, greenhouse climate control is a challenging task, because greenhouses have highly interactive nonlinear dynamics and model uncertainties and are subject to input saturation. In light of the fact that Iran is a country with a warm and arid climate, tunnel greenhouses equipped with evaporative cooling system are very common in Iran. Accordingly, this type of greenhouse is considered for modelling, simulation and control in this... 

Since the early 90s, nanotechnology has contributed to several developments in a wide range of Science and industry such as medicine, Physics, Chemistry, Aerospace, electronics and Biology. In recent years, nanotechnology has also made development in the oil and gas industry. The drilling fluid is already one of the most important parts in drilling operation.The physical properties of a mud, rheological properties and minimize fluid invasion into the formation with perfect mudcake are important to assist in optimizing results. Nano-materials as one of the achievements of recent years are effective in achieving these purposes. To obtain the above properties, a variety of polymers as... 

Constant drilling in the shale formation causes many problems such as shale swelling and well instability. Annually many costs are spent dealing with these problems in the drilling industry. Many factors can affect this issue. The most important factor is the type of drilling fluid and its additives. The use of oil-based mud is the best option to deal with the clays instability but, due to environmental problems resulting from OBM, their use has been banned in most parts of the world. Therefore, the water-based mud is the only option for the oil industry that can modify its property by use of additives. In this study, the muds contain Nano silica have been introduced. Silicate as shale... 

To keep up with the growing demands for energy, the oil and gas industry ventures into deeper waters. This increases complexity of offshore projects. Part of this complexity is due to the resistance of a pipeline against local buckling collapse due to external pressure that is more significant in higher pipe laying depth and consequently higher external pressure. Pipeline response to external pressure is an important factor in design of marine pipeline.Local buckling of a pipeline is the buckling behaviour within the pipeline cross section. Other types of buckling behaviour such as upheaval and lateralbuckling are not in the scope of this thesis.In this thesis, the installing pipeline is... 

Scheduling has been an active area of research for decades. A substantial amount of work has been done to define, classify, and solve scheduling problems. Most of these problems are computationally difficult to solve, and incorporating other decisions into them increases the complexity of these problems. This thesis focuses on order acceptance and scheduling (OAS) problems, and proposes time-indexed mixed integer and linear programming (MILP) models for the first time. An OAS problem can be defined with parameters of processing time, release date, due date, and deadline for each order. There are also a maximum revenue that will be brought by each order and an importance weight of each order.... 

The Ni-based superalloy GTD-111 possesses excellent hot corrosion resistance, high stability and strength at elevated temperature; accordingly, the alloy is used in manufacturing of the first stage blades of powerful gas turbines. In this study, effect of withdrawal rate from Bridgman furnace and precipitation hardening on the microstructure and microhardness of this superalloy were investigated. To this end, several experiments were carried out under growth rates of 1, 6 and 10 mm/min using Bridgman process under vacuum. Afterwards, the effects of homogenization treatment, partial dissolution with two different cooling rates (air and water) along with aging on the microstructure were...