Sharif Digital Repository

The main purpose of this study was to increase the flow circulation within the flat plate oscillating heat pipes as a result Increase the heat transfer rate by placing diagonal grooves in the evaporator. The project in two stages a simple page and diagonal companion page are provided to investigate the effect of diagonal grooves. First a simple plate and then a second one with diagonal grooves in the evaporator it was made. Thermal performance of the heat pipes at each of the stages at different filling ratios of 40%, 50%, 60% and 70% for variable input capacities have been studied and compared. The results of the second stage showed that the performance of the new heat pipe at the optimum... 

Brain Computer Interface (BCI) is a communication system between human brain’s activity and his environment such as prosthetic hand and wheelchair and other controlling devices.In this thesis we will introduce a new and easy spelling system by using Brain Computer Interface (BCI) based on Steady State Evoke Potential (SSVEP). This system is used for spelling the numbers of telephone keyboard by four flickers and clock shape. This system allows the user to spell numbers by gazing at one of four flickers (Clockwise rotation, Counter Clockwise rotation, Accept and Backspace), Clockwise is used to rotate clock hand toward right, Counter Clockwise to rotate clock hand toward left, Accept is used... 

Brain Computer Interface (BCI) is a communication system between human brain and a computer or a peripheral device which by recording brain signals directly would send messages and commands from the human brain to computer.According to brain activity patterns of EEG, BCIs are divided into different types. The most important of these patterns called ERP (Event Related Potentials) which appears after particular events in the EEG signal. A significant ERP pattern is P300 potential. It occurs when patient recognizes oddball stimuli. SSVEP (Steady-State Visual Evoked Potential) is another type of patterns and is response of the brain to optical stimulations with certain frequencies and a strong... 

Nowadays, the use of MEMS sensors, due to their small size, lightweight and low cost, has been welcomed in systems such as autonomous vehicles. Although the precision of MEMS gyroscopes has been extremely improved, in some aspects, such as stability of bias, they still suffer from some big error sources, like run-to run bias, which determines the sensor price but is not negligible even inexpensive sensors. In addition to the bias, there are a lot of noises in the gyroscope outputs, where ARW is one of the most important ones, which causes failure in real-signals and produces an error in the position and attitude of mobile systems. Due to the fact that run-to-run bias and ARW are stochastic... 

Simulation of biophysical neural networks enables the interpretation and integration of fast-growing and different experimental datasets. The widely used NEURON simulator allows molecular-to-network simulation. However, it is still a very hard challenge to create large-scale models and operate parallel simulations applying NEURON. SUNY Downstate developed the NetPyNE means networks using Python and NEURON, which was funded by the New York State Department of Health and some other institutions. NetPyNE is a Python-based tool that enables the development of data-driven multi-scale network models in NEURON through both programmatic and graphical interfaces. It is a powerful tool for parallel... 

The main purpose of the current study is to control the boundary layer of the flow passing over the wing and the lift force enhancement. In this research has been tried to introduce a new generation of passive flow control and use bumpy surface structures to control the separated flow and increase the aerodynamic efficiency. Therefore, the wing with the hawk bird’s airfoil section has been designated. Then, assuming a viscous, incompressible flow and a low Reynolds number range (about 2 × 105), the flow formation and boundary layer development on this wing has been investigated. Subsequently, bump structures have been settled on the upper surface of this wing. The numerical simulations have... 

In this thesis, a method is presented for improving the observability of the heading angle in a UAV when using the Visual-Inertial navigation algorithm MSCKF by adding a magnetometer sensor. The proposed algorithm serves as a complementary extension to the primary algorithm, and efforts have been made to seamlessly integrate the magnetometer sensor into the primary algorithm to allow for easy modifications to the sensor's characteristics and to observe the resulting output in system simulations. Improving the observability of the heading angle will lead to an enhancement in the overall system state estimation. To achieve this, a new update stage is added to the existing algorithm.... 

In this research, inspired by the navigation system of insects, a method for extracting the navigation information required for an autonomous device is presented, with an information input section in the form of image processing using optical flow and an information processing section with an artificial brain structure. In this method, the information obtained from the optical flow is processed by the neural network structure and the navigation information needed to control and guide the autonomous device is obtained. There are several methods to estimate the optical flow between two frames, in this research, the DEQ-Flow optical flow estimation network, which is a method based on deep... 

In this thesis, the physics related to liquid jet injection from injectors with three different crescent-shaped cross-sectional levels into steady and transverse flow were studied. The imaging method in this research was based on shadowgraph, which enables high-speed imaging. With the help of the obtained images, the breakup regimes, including Rayleigh, first and second wind-induced instabilities, were observed for injection into the steady flow. Furthermore, breakup regimes for jet injection into transverse flow, including columnar, columnar-bag, and bag, were also observed. The characteristics of the breakup height in steady flow and the length and height of the breakup along with the jet... 

A projectile was tested in a wind tunnel at various free sream Mach numbers and angles of attack. The tests were carried out at the transonic wind tunnel of the Imam Hussein University.The experiments were performed at subsonic and supersonic speeds and at different angles of attack. The aerodynamic behavior of the model was investigated using force and moment measurements. The results showed that in the range of measured angles of attack the separation did not occurr and variations of lift coefficient remained linear for all Mach numbers except for a free stream Mach number of 2.0. For this Mach number, the asymmetric bow shock makes a pressure difference between leeward and windward sides,... 

In small turbojet engines, it is important to find a suitable fuel injector with good spray quality. However, the rotating fuel injection system can potentially provide high atomization quality without the high-pressure fuel pump through the centrifugal forces of the engine shaft. The spray characteristics of rotary atomization for small gas turbines can be investigated using a high-speed camera. To analyze the breakup process of the liquid column and liquid film, spray visualization tests should performed under varied test conditions.In this research, experimental study on liquid breakup process has performed in rotary atomizer of j402 turbojet engine with the name of slinger injector, to... 

In this research, it has been trying to implement Virtual Structure method for formation flight of multiple spacecraft. In this method, a virtual solid frame with virtual center of mass is considered and agents are arranged in a formation with respect to the virtual center. In this work, a formation keeping control system is implemented in which a feedback from formation to virtual structure and vice versa is considered. The method is implemented firstly in a nongradient field and then developed into a circular orbit in order to investigate the in-orbital effects. An algorithm for collision avoidance, based on relative distances and relative velocities, was also developed. The algorithm was... 

The highest and most difficult layer of Natural Language Processing, is the understanding of meaning. As a result, lexicons and annotated corpora are of the utmost importance in this area. However, the lack of such semantic resources, especially in Abstract Meaning Representation (AMR), is one of the main issues in this field for Persian Language. This work by modeling PropBank, a semantic valency lexicon for English predicates, is the first step towards building such lexicons for Persian Language with the focus on AMR. Thus, a guideline describing how to annotate the Persian predicates is provided which first evaluates the common structures between the two languages and then focuses on the... 

The importance of having a rich repertoire of vocabulary at one’s disposal is evidently an undeniable fact for a successful communication. However, the best way to improve the lexical knowledge of the students is an issue that is still open to dispute. Considering this issue the present study focused on vocabulary learning strategies in L2 teaching. Actually, this study aimed at investigating three different methods of teaching new words to Iranian students in order to determine which one of the methods is more effective in terms of immediate and delayed retention. So the researchers strived to examine the question of how two different mnemonic devices, i.e., the Keyword method and the... 

Human visual attention is a mapping that determines to what regions of an image human’s eyes focus more while perceiving it. Personalized visual attention is visual attention computed for a specific individual. The importance of visual attention lies in its wide range of applications in computer vision and cognitive science, such as neural encoding, image captioning, self-driving cars, video anomaly detection, image classification, and visual design. One of important aspects of visual attention is personalization, the ability to assign every individual their own, specialized attention map. In this project we aim to utilize EEG signals measured from people’s brain to predict their... 

Creative play is both engaging and educational. Finger painting, building with blocks, drawing, or dressing up – all such activities intimately link imagination and self expression with exploration and problem solving. With creative play, children have fun while learning new skills and enhancing their understanding of the world. However, with the popularity and ubiquity of digital devices, an increasing amount of play time happens in the digital world, such as with video games where the link to creativity is sometimes questionable. Instead of creative play, children simply play. In this thesis, we describe the design, development and preliminary evaluation of a novel animation tool for... 

Visual Question Answering (VQA) deep-learning systems tend to capture superficial statistical correlations in the training data because of strong language priors and fail to generalize to test data with a significantly different question-answer(QA) distribution. To address this issue, we introduce a Visually Directed Question Encoder to replace the commonly used RNNs in base models. our method uses visual features alongside word embeddings of question words to encode each word. As a result, the model is forced to look at the visual information relevant to each word and it no longer produces answers based on just the question itself. We evaluate our approach on the VQA generalization task... 

Primary visual cortex plays a paramount role in processing visual information. Visual information after the primitive processing by LGN and Thalamus, will be sent to the primary visual cortex which is called V1 area. According to the fact that V1 neurons have the definitive sensitivity to the edge and contrast of visual stimuli so their behavior are very selective to the certain features, specially contrast, of visual stimuli. These neurons have different response behavior to contrast. In fact most of them have some nonlinear behavior to this feature. Normally we expect that response of them or spiking rate of them grow linearly by the contrast increases but in most many cases they have some... 

Melanoma is a malignant skin cancer which is caused by cancerous growth of melanocytes. If not treated at its early development stages, melanoma is the deadliest form of cancer. The best way to cure melanoma is to treat it in its earliest stage of development. Since a melanoma leasion is similar to benign moles (regaring its shape and appearance) at its early stages of development, it is often mistaken for moles and left untreated. Therefore, automatic melanoma detection can increase the survival rate of patients by detecting melanoma in its early stages. In this thesis, a new method for automatic diagnosis of melanoma using segmented dermoscopic images is provided. Almost all related... 

The growth of the knowledge of image processing and machine vision in recent years has led to many applications in various fields. One of the most important applications in machine vision is automotive navigation of vehicles and robots. The effective use of visual sensors to detect obstacles, routing, detecting the position of the robot, and mapping the environment is one of the most important goals in ground robotics. Few methods using sensors such as accelerometers, gyroscopes and global positioning systems, suffer from problems such as high costs, accumulative errors, dependencies on external systems, and the inability to be used in closed spaces. But with the use of the visual sensors,...