Sharif Digital Repository

The problem of attitude determination (AD) has always been a challenging issue for space missions that is of importance either independently or for attitude control purposes. The problem of AD is generally focused from two aspects: measurement mechanisms (sensoring) and determination algorithms. From the former point of view, there exists a variety of measuring systems such as the Sun sensors, magnetometers, gyroscopes, star and horizon sensors that have been separately or collaboratively utilized for AD. Integrative usage of sensors not only can bring about added advantages in terms of accuracy, but also provides for estimates of attitude during special times such as the Sun eclipse. The... 

The current research is devoted to the design and optimization of a Blended Wing Body aircraft configuration in the conceptual design phase. In this respect, two objective functions with eight design variables have been considered within the optimization process in order to reach to a desired design. The key objective functions include the aerodynamic efficiency as well as the aircraft empty weight alongside the longitudinal stability requirement that are accounted for within the Genetic algorithm optimization loop. In this regard, some analytical and semi-empirical relations are utilized to determine the aerodynamic and structural characteristics of different designs alongside the numerical... 

Environmental problems and limitation in fossil fuels have increased the application of renewable energy sources (RES) and distributed generations (DG). Due to the DC nature of most loads and DGs, DC microgrids provide a suitable structure to integrate different kinds of DGs and loads. Undesirable voltage regulation and poor power sharing among the sources in conventional voltage-based control methods are solved by the superimposed droop frequency method. However, the superimposed droop frequency scheme suffers from three major problems which are (i) instability in terms of load variation, (ii) limitation in the system maximum loading which is due to the limitation in the transferred... 

In the present study, performance of a novel fan namely bladeless fan has been evaluated. The aerodynamic and aeroacoustic performances are studied by using 3D simulation of this fan. Mass conservation equation, momentum conservation equations and noise equations of FfowcsWilliams-Hawkings numerically solved to investigate performance of this fan. Firstly, fan cross section profile was designed by Eppler airfoil 473 instead of the prior profile as a modification then effect of different geometrical parameters on the performance is examined. These parameters are height of cross section, angle of output flow with respect to fan axis, thickness of output airflow, hydraulic diameter and aspect... 

The rapid growth of computer networks has increased the importance of analytics and traffic analysis tools for these networks, and the increasing importance of these networks has increased the importance of security of these networks and the intrusion detection in these networks. Many studies aimed at providing a powerful way to quickly and accurately detect computer network intrusions, each of which has addressed this issue.The common point of all these methods is their reliance on the features extracted from network traffic by an expert. This strong dependence has prevented these methods from being flexible against new attacks and methods of intrusion or changes in the current normal... 

The stress positions of the words are determined according to the type of their morphological elements. Persian Words often have a fixed position for stress. However, Persian wordforms show different stress positions, based on their morpheme types or in the other words, their bound-non derivational affixes. Inflectional affixes accept stress, whereas clitics do not. In the present research we studied both types of non derivational affixes considering their phonetic features meaning fundamental frequency and duration. The phonetic representation of the pitch accent as the phonemic- intonational element was given as a result of this study, as well. The differences in the phonetic... 

Fire incidents are more prone to happen in tunnels characterized by varying curves, aspect ratios, and slopes, influenced by the geographical features of the land. To simulate diverse fire scenarios, a three-dimensional computational fluid dynamics code utilizing curvilinear grids adapted to the tunnel's structure was employed. The simulations involved heat releases ranging from 5 to 60 MW in a tunnel with a turning radius of 100–1500 m, an aspect ratio between 0.5 and 2, and a slope ranging from -10% to 10%. Applying the Design of Experiments (DOE) method in conjunction with numerical simulations, thirty-two 3D numerical models were generated, leading to the development of a second-order... 

A triple antibiotic mixture (ciprofloxacin, metronidazole, and minocycline) has been used for dental root canal medicaments in pulp regeneration therapy. However, tooth discolorations, cervical root fractures, and inadequate pulp-dentin formation have been reported due to the triple antibiotic regimen. Therefore, antibiotic containing scaffold has been developed to minimize the clinical limitations and maximize a natural healing process in root canal infections. The ideal controlled release drug device should have the following characteristics. It should not degrade inside the root canal and it should be easily inserted into and removed from the root canal. In addition, the drug should be... 

We live in the cyber era in which network-based technologies have become omnipresent. Meanwhile, threats and attacks are rapidly growing in cyberspace. Nowadays, some signature-based intrusion detection systems try to detect these malicious traffics. However, as new vulnerabilities and new zero-day attacks appear, there is a growing risk of bypassing the current intrusion detection systems. Many research studies have worked on machine learning algorithms for intrusion detection applications. Their major weakness is to consider the different aspects of network security concurrently. For example, continuous concept drift in normal and abnormal traffic, the permanent appearance of zero-day... 

Membership inference attacks are one of the most important privacy-violating attacks in machine learning, as well as infrastructure of more serious attacks such as data extraction attacks. Since membership inference attack is used as a measure to evaluate the level of privacy protection of machine learning models, different researches have investigated and provided new methods for this attack. However, the accuracy of these attacks has not been investigated on models trained with the latest techniques such as data augmentation and regularization techniques. In this research, we see that the Lira attack, the latest membership inference attack, which has much more power compared to previous... 

In a GAN, the generator receives random noise data and produces outputs similar to real data. The generated output data, along with the original dataset, is fed to the discriminator, which distinguishes between real and fake data. The two networks have opposing objectives, but they help each other learn in practice, continuously improving each other's performance. Each of the two networks aims to minimize its own error while maximizing the other's error. John Nash mathematically proved that the optimal solution to these problems occurs when neither agent can further increase its utility. This situation is referred to as Nash equilibrium. If the training data is limited, the GAN cannot... 

Wars are destructive and ruin lives. However, when it comes to defending one’s home country and religion, the brilliant aspects of sacrifice are highlighted. The 1980 war between Iran and Iraq, which lasted eight years and cost more than 200,000 lives, is a prime example of such sacrifices. Religions demand sacrifices and create club goods like altruism, cooperation, and effort, which are crucial on the battlefield. Religious institutions, like the Imamzadehs in Iran, strengthen people’s faith and play a significant role in these sacrifices. About eight thousand Imamzadehs in Iran are tombs of the grandchildren of Prophet Muhammad, who left the Arab land seeking a peaceful life among... 

Many regulations have been introduced over the world to urge the elimination of lead and lead containing solders, due to increasing pressure of the environmental and health concerns associated with lead-containing solders in the electronics industry. Therefore, efforts to develop and promote lead-free soldering have recently intensified. Conventional solder technology may not guarantee the required performance at such pitches due to problems such as higher diffusivity and the softening nature of the solder. To solve these problems, efforts have been made to develop solders with a low melting point, higher strength, better microstructure properties, and high creep resistance. Recently... 

In this thesis, a laminated composite beam with single delamination under the action of moving force/oscillatory mass has been modeled and analyzed. The beam has been divided into four sub-beams and based on Bernoulli-Euler and also shear deformation theories and by applying the Hamilton’s principle, equations of motion along with boundary conditions and continuity and compatibility conditions are obtained. Primarily, based on the constrained mode model the delaminated layers have been analyzed then by implementing the Lagrange multipliers method, the nature of dynamic contact is incorporated. In the analysis of delaminated beam based on the constrained mode, by applying the mode summation...