Sharif Digital Repository

The primary objective of this thesis is to provide solutions addressing some security loopholes in continuous variables quantum key distribution protocols. The coherent detection method is utilized in this particular quantum key distribution scheme, which is a phase-sensitive detection. To measure in the quantum noise limit in the detection part, we need a local optical oscillator, which must possess a high intensity and a consistent phase correlation with the quantum signal. Therefore, reconstructing the emitter’s reference phase in the receiver’s detection system is considered as one of the most critical challenges in these protocols. In order to attain this goal, in the early versions of... 

In this thesis, we introduce a novel Artificial Intelligence (AI) system inspired by the philosophical and psychoanalytical concept of imagination as a ``Re-construction of Experiences". Our AI system is equipped with an imagination-inspired module that bridges the gap between textual inputs and other modalities, enriching the derived information based on previously learned experiences. A unique feature of our system is its ability to formulate independent perceptions of inputs. This leads to unique interpretations of a concept that may differ from human interpretations but are equally valid, a phenomenon we term as ``Interpretable Misunderstanding". We employ large-scale models,... 

According to today’s medicine progress, the need for improving the medical facilities have been increased. Within the human body, the biomolecules concentration gradient is regulating the cell functions. Biological processes such as immune response, wound healing, and cancer metastasis have been affected by the bimolecular concentration gradient. So understanding the cell behavior in the presence of a chemical gradient can improve the understanding from these biological processes, and also would help in medical researches. On the other hand, finding the appropriate dose of the drugs and in some cases finding the most effective drug is a clinical challenge that made a new field of research in... 

In this Thesis we study the string theory discription of non-relativistic quantum ?eld theories.In other statement we study the duality between gravity and gauge theory with non-relativistic symmetry.We discuss that this duality works in non rel- ativistic sense.We study two kind of non-relativistic theories that one of them camefrom string theory and other model obtained by special transformation of original relativistic theory and we see that how duality can be work for these models.Also dual picture of semi-classical string in the background that found from string theorystudied.We also study the motion of particle in a hot plasma and we ?nd a sign of non-relativisic duality really works  

In last decades as the international volume of trade increased significantly, examination of the relationship between trade and economic growth is one of the interesting topics for economists and policymakers. Trade can affect performance of economics by many channels, such as trade specialization, human and physical capital accumulation, knowledge and technology transfer. In this regard the aim of this thesis is the examination of trade specialization in industries with high productivity (as one of the trade influences) effects on economic growth.In this research based on Hausmann et al. (2006), we use an economic model with two sectors: modern and traditional. This model gives a primary... 

In this thesis, design and fabrication of wide band frequency synthesizer with low spurious and low phase noise is investigted. It is very important to use an apropriate frequency synthesizer structure which would meet intended properties. In order to reach a low step size and high switching speed, using DDS is recomended; as well as using composition of DDS and PLL in order to meet a low spurious level. The main objective of this thesis is to investigate the best composition of outlet spures; so beside optimization of other properties, the main motivation has been focused on decreasing spures. Moreover, after studying Mechanisms of spures production in DDS outlet, some methods for... 

The development of clean, renewable and alternative sources of fossil fuels has increased in recent years due to various factors such as environmental pollution, reduced fossil fuel resources and increased energy consumption. The application of microbial fuel cells is one of the clean energy production methods using renewable sources such as municipal sewage. The microbial fuel cell converts the chemical energy stored in organic materials into electrical energy and simultaneously purifies the sewage. Increasing current density and power density are the most important challenges for microbial fuel cells. In this study, the two biocatalysts of Shewanella Oneidensis MR1 and Escherichia coli... 

In this thesis, chaotic behavior of a photonic micro-resonator is investigated. First, a Lagrangian formulation is introduced for the system. Then, by applying a multi-reflection method, a closed formula is obtained for the radiation pressure. Use of this equation in the coupled differential equations describing dynamics of the problem gives us a suitable model for exploring the behavior of the micro-resonator. In this stage, we compare our results with experimental data too. On the other hand, using above mentioned formulation, chaotic behavior of the micro-resonator is investigated using numerical method. Finally, a period-doubling route to chaos appears in our results as is observed in... 

Magnetite (Fe3O4) nanoparticles were synthesized and coated with Oleic Acid using the co-precipitation method. The particles were characterized using DLS, FT-IR, SEM, XRD, VSM and UV-Vis spectrophotometry analysis. The mean size of particles was 28.8 nm and the FT-IR analysis indicated that Oleic Acid was coated suitably on the nanoparticles. The vsm test indicated no hysteresis loop for the particles, defining the superparamagnetism of them. A nanofluid containing nanoparticles in 5wt% Acetic Acid in Toluene as the base fliud was prepared. The stability of this nanofluid was determined using UV-Vis spectrophotometry to be less more then 95% in the first two hours. This nanofluid is used as... 

This thesis focuses on the development of a flight formation control algorithm and obstacle avoidance of a UAV team using fuzzy predictive artificial potential field (FPAPF) method. One of the common methods for path generation and obstacle avoidance is the artificial potential field (APF) method. The basis of the APF method is that the UAV is attracted to the target point and repelled from the obstacles by using the potential fields of attraction and repulsion. The popularity of this method is due to its computational simplicity and efficiency. The APF method has limitations due to constant attraction and repulsion coefficients. The proposed real-time FPAPF method uses fuzzy logic to... 

Surface plasmons are the result of a resonant interaction between the waves and the mobile electrons at the interface between negative and positive permittivity materials stimulated by incident light. Due to their specific quantum mechanical nature and zero electrical resistance, superconductors are capable of supporting low-loss plasma waves with extremely large propagation length. In this study, palsmon confinement in some superconducting waveguide structures has been measured by computing the effective index parameter. Superconductors are classified in to high-Tc an low-Tc categories. It is not possible for plasma waves to propagate in low-Tc superconductors, because the plasma energy... 

This study examines the relationship between the number and diversity of complementary products and the success of video game platforms. The primary question of this research is why platforms like the PlayStation 5 have achieved widespread success, while other lesser-known platforms have faced failure. Do the depth and breadth of complementary products offered on platforms, as suggested by theories in the platform literature, explain this success? The findings of this research can help companies in the video game industry and related sectors better understand the factors influencing platform success and make more targeted investments in complementary products. Furthermore, this study holds...