Sharif Digital Repository

Chaos in dynamical systems refers to the presence of extreme sensitivity to initial conditions in the system’s behavior, which renders the long-term prediction of the sys- tem’s behavior either impossible or highly challenging. This chaotic behavior is also present in deterministic systems. The observation of this concept, besides philosophical changes it has brought about, has been scrutinized in various domains and has provided an explanation for many observed physical, chemical, and biological phenomena. This phenomenon has been studied in diverse sectors such as fluid dynamics, neuronal dy- namics, and chemical reactions. In this research, we intend to analyze chaotic dynamical systems... 

Pronoun resolution is one of the challenges of natural language processing. The proposed solutions range from heuristic rule-based to machine learning data driven approaches. In this thesis, we followed a previous machine learning base work to Persian pronoun anaphora resolution. The primary goal of this thesis was to improve results, mainly by extracting more balanced data and to add more features to the extracted feature vectors used in classification. Using PCAC2008 dataset, we considered noun phrase structure as a way to extract more suitable training data. Features added to the extracted data include syntactic and semantic features. Then, we trained and tested different machine learning... 

The Self-Consolidating (Compacting) Concrete (SCC) is a high performance concrete. Due to preventing it from segregation, SCC is known by its need to higher dosage of super plasticizer and viscose modifying agents. This increases the cost and reduces the popularity of SCC in construction industry. In this thesis, the production of Rice Husk Ash (RHA) from a controlled burning process using a special designed furnace, and cement replacement feasibility in the concrete mixture by low cost RHA, as an active pozzulanic additive have been investigated. Finding an appropriate ratio of replacement with cement for RHA and further effects on mechanical properties of SCC have been evaluated. The... 

Chronic kidney disease is one of the silent diseases that progresses slowly, often without symptoms, and can eventually lead to kidney loss. Early detection of this disease can help diagnose it and prevent further problems. Urinary creatinine is an effective biomarker for early diagnosis of chronic kidney disease, but methods available in clinics are problematic for people living in disadvantaged areas because of the high cost and the need for 24-hour urine collection. Currently, paper-based microfluidic devices are being developed because they are easy to manufacture, inexpensive, the fluid is permeable by capillary force, and no additional equipment is needed. In this work, to fabricate a... 

For over a hundred years, vehicles have entered the human environment and influenced it. One of the most important effects that vehicles have on their surroundings and humans is their acoustic noise. The gearbox is one of the important components of the vehicle's transmission chain, in which the gears interact with each other and cause to create noise and vibration. These vibrations are transmitted through the bearings to the gearbox casing and then transferred to other parts of the vehicle via gearbox supports. Many researchers have studied the factors of NVH production in gearboxes and used methods such as gear profile modification and optimization of shaft and casing to reduce NVH. This... 

A key point in designing class-C oscillators is maximizing the Figure-of-Merit (FoM). For this purpose, changing the oscillator’s structure or adjusting its bias current may be used. Previous literatures mostly limit their efforts to the first case, leaving the issue of determining the proper bias current almost untouched. In this work, a new approach recruiting DC voltage of the common source node of the switching pair transistors as an indicator has been presented. Using theoretical analysis, it has been shown that maximizing this voltage will optimize the oscillator in term of the FoM. The proposed indicator has the advantages of not introducing any loading effect to the output node, and... 

The primary purpose of acidizing operations in the oil and gas industry is to enhance hydrocarbon production. Acidizing has been a common and conventional method for years, especially when production engineers face issues like declining reservoir pressure leading to reduced production rates. Initially, the treatment solution is referred to as matrix acidizing. In acidizing operations, different additives are combined with the acid to control its behavior in the reservoir. These additives may include iron control agents, corrosion inhibitors, friction reducers, and more. Incompatibility among these additives, the acid, and reservoir fluids can lead to severe damage to the reservoir.... 

The goal of this research is the simulation of the annular combustion chamber of the turbine engine utilized by liquid fuel. The achievement to this goal will lead to create numerical tools for parametric study, analysis and combustion chamber designing.For this reason simple geometry has been considered. This simplicity of geometry causes to facilitate in parametric study and decrease in saving time for modeling and meshing. This combustion chamber is a simplified model of engine CF6. In recent study, the k – ε realizable model has been used for turbulence modeling. For non-adiabatic condition, chemical reaction is dissolved by utilizing probability density function along with laminar...