Sharif Digital Repository

In the context of differential privacy, a data holder has confidential information about users. The goal is to provide a randomized algorithm that takes this information as input and outputs an aggregation of the input. The algorithm must have the property that for any neighboring input pairs, the output distribution of the algorithm is close. One problem in differential privacy research is the release of shortest distances in a weighted graph. This model, first studied by Adam Sealfon, involves an edge-weighted graph G=(V, E) with weights w : E → R, where the topology of the graph is public and the private information is the weight of the edges. The aim is to provide an (ϵ, δ)-DP algorithm... 

Fiber optic sensors have found industrial applications due to their unique characteristics and wide range of environmental parameters. Specifically, distributed optical fiber sensors which have applications in borders protection, intrusion detection, oil and gas leakage detection and smart irrigation of farms and gardens, have attracted significant attention from research groups around the world in recent years. According to the forecasts, among all kind of optical fiber sensors, the temperature and acoustic/vibration sensors will seize the market during the coming years. In this thesis, three kind of optical fiber sensors are proposed for environment health monitoring. First, distributed... 

One the most important issues in most of embedded systems is reliability and fault tolerance.Ensure of correct operation and evaluate reliability and fault tolerance of embedded proces-sors as a critical part of embedded systems, would be necessary. Fault injection is one themostly used methods for evaluating those features. Using FPGA devices is a good alterna-tive for time consuming simulation-based fault injection method because of their speed. But,there are some critical issues in FPGA-based fault injection methods which are controllabil-ity and observability. In addition to need for efficient and applicable observation and controlmechanism to handle fault injection experiments, a... 

Quantum key distribution is one of the practical quantum information technologies in labo- ratories with existing equipments.In quantum key distribution protocols, the main challenge is the secrecy of key distribution. One of the new methods of quantum channel error esti- mation is the use of weak measurement. In this thesis, after introducing the main quantum key distribution protocols, we introduce weak measurement and sequential weak measure- ment concepts: the weak measurement methods are exployed to obtain the phase difference between two polarizations with high accuratly. It is also used for in line monitoring and error estimation parameters in some quantum key distribution protocols.... 

In this thesis, we present some extension of Burton and Kirk fixed point theorem for the sum of two nonlinear operators, which one of them is compact and the other one is strict contraction; and we investigate the existence of fixed point where these two operators don’t need to be weakly continuous. Next, we will check the necessity of some conditions, like being strict contraction or compactness, in some specific Banach spaces, such as reflective spaces or Banach spaces equipped with uniformly convex norm.Finally, we analysis the existence of the solution for integral equations in L1 space by using the expressed theorems  

Most propulsion systems use nozzles to increase the velocity of exhaust gas. Therefore, the efficiency of nozzles is important. Losses due to geometry and physical phenomena inside the nozzle define this efficiency. The length and divergence angle of the nozzle, the throat diameter, the Reynolds number, and the specifications and the combinations of fuel have a direct impact on these losses. Solid propellant rockets are widely used and today optimization of rockets is most noticeable. On the other hand, in different phases of design and optimization, empirical experiments are necessary, which are costly in real dimensions. The use of laboratory motors with specific considerations decrease... 

Nanolaunchers are launch vehicles capable of carring light payloads (under 50 kg) to Low Earth orbit and received much attention in the few past years. Launching the nanosatellites grown about 30 times from 2008 to 2017. Since this category of launch vehicles has fewer developing costs and lower thechnology level, they fit developing space technology in our country. Conversely, the demand of high propellant mass fraction and specific impulse may be a serious difficulty to attain this technology.The only operating nanolauncher in the world is SS-520-5 which belongs to Japan and is a three-stage solid propellant launcher. The goal of this project is also the conceptual design and feasiblity... 

This thesis is conducted to study acceleration effect on the burning rate augmentation of a solid propellant. A centrifugal experimental setup is designed to obtain a uniform acceleration field. An internal burning tube is used as grain, so acceleration vector is always perpendicular to burning surface of propellant. Inner radius of tube is small, so the magnitude of acceleration increases as the grain burns back. The pressure of combustion chamber was changed from 30 bar to 80 bar by changing the nozzle throat and the magnitude of acceleration changed from 2g to 60g by changing the rotational speed of SRM. Burning time of all tests was below 2 sec. due to small web of the grain. Pressure of... 

Aquatic plants play an important role in water environment. Increasing drag force, distorting the velocity and turbulence structures and other related parameters, are the results of the presences of plants. These changes affect the dispersion and mass transport in the aquatic areas. This thesis presents laboratory visualizations and measurements of wave motion, and passive solute surface dispersion (longitudinal and lateral) in arrays of cylinders, a model for emergent, rigid aquatic plants. In the range of (where is Keulegan–Carpenter number, is the maximum oscillatory velocity perpendicular to the cylinder axis, is the period of oscillation, and is the diameter of the cylinder), and (where... 

The aim of this study is to remove pharmaceutical pollutants through a photocatalytic approach. A layered double hydroxide (LDH) structure was synthesized with the assistance of a metal-organic framework (MOF). Initially, MIL-101(Cr) was synthesized using trivalent chromium ions and subsequently transformed into a layered double hydroxide structure with divalent nickel ions. To further enhance this process, MIL-88(Fe) was prepared using trivalent iron ions, composited with MIL-101(Cr), and then converted into an LDH structure using divalent nickel ions. The resulting photocatalytic composite was fully characterized, and its efficiency in degrading the pharmaceutical compound meropenem was... 

Over the years, as machines have been invented, their maintenance and repair have consistently been regarded as critical concerns. Oil analysis techniques are an effective method for monitoring the condition of mechanical equipment. Since filters in these devices continually absorb and remove a significant portion of particles from the lubricant, the selection of appropriate filters is crucial. While filters positively affect machine performance, they can also negatively impact oil condition monitoring. To mitigate this negative effect and improve the predictive accuracy of equipment health monitoring, oil filter analysis was conducted. In this research, analytical ferrography tests were... 

Nowadays, with the expansion of restructuring and privatization in power systems, energy markets are growing rapidly, within distribution networks. In order for such markets to be implemented in practice, the technical constraints and issues of the distribution network, which are mainly the power loss and congestion of lines and also the bus voltage violations, must also be considered within the framework provided for them. Hence, this dissertation presents some new structures for Peer-to-peer (P2P) energy markets, in which the technical issues of the distribution network could be considered. Moreover, a model predictive control method is used in the proposed structures of this dissertation...