Sharif Digital Repository

One of the serious challenges we are facing in making quantum computers is the quantum error correction. Whereas system interact with the environment, quantum states are easily inf luenced and are suf fering f rom noise and error. T his makes the act of quantum computing be disrupted.T heory of quantum error correction has emerged for facing such a serious challenge. In this theory, many ways that are combined with several branches of mathematics were invited that are essentially dif ferent to classical error correction. one of these is stabilizer codes that show a rich structure and simple f rom classical error correction codes and in addition many quantum error correction codes can be... 

Medical images contain information about vital organic tissues inside of the human body and are widely used for diagnoses of diseases or for surgical purposes. Image Reconstruction is essential for medical imaging for medical systems like suppression of noise or de-blurring from projections in order to have images with better quality and contrast. Due to the vital role of image reconstruction in medical sciences the corresponding algorithms with better efficiency and higher speed is preferable. Most algorithms in the field of image reconstruction are operated in frequency domain such as the filtered back projection which is a popular algorithm for the reconstruction of the medical images. In... 

The only problem in aviation and airport development is the noise print on population groups surrounding airports due to its high frequency it is so annoying for human ear. In order to overcome this problem technology has reached its edge and the only alternative is to deviate terminal flight path.In this thesis I tried find a pattern for optimizing terminal flight path considering a Boeing 737-800 taking off from Mehrabad airport’s runway 29. To do this we were in need of a huge database of airplane low speed model, geographic information and population knowledge.The common approaches used by FAA and other international organizations for modeling low speed flight were used. The influence of... 

We present a novel and simple method to calculate each Fourier series coefficient of ISFs in LC oscillators, analytically. This new approach explains the relationship between Fourier series coefficient of ISF and oscillator topology and parameters. This technique helps designers to obtain the great insight of how to decrease the output noise in oscillators. This method also can be used to derive the waveform of ISFs in time domain.Based on the features of our new technique and by presenting a general method to change the stationary noises to Cyclo-stationary ones, we suggest a step by step design guide which elucidates new ideas for designers to manipulate the oscillator parameters and... 

Detectors play an important role in almost all scientific experiments and the results of the experiment highly depend on the performance of the applied detector (e.g. the detector detectivity, noise, detection threshold, time constant, …). In general a detector is defined as a device which transforms a quantity (e.g. pressure, energy, photon, …) to another one(e.g. mechanical displacement, electrical current, voltage, …). High temperature superconductor transition edge bolometers (TEB) are one of the most promising devices that due to the wavelength independent nature of their optical response can be used to detect the electromagnetic radiation over the whole spectrum from x-ray to the far... 

Noise phenomena, which is considered as a nuisance factor, always acts as a barrier to achieve optimal performance in all systems. In Nuclear power reactors, noise can occur due to mechanical problems such as fluctuation in control rods, failure in placing Fuel assembly in their locations properly or other factors such as creation of small bubbles in moderator. Regardless of its cause, noise leaves its impact on cross section area of material within the reactor core. Change in material cross section area shows its effect in neutron flux. Although noise is a small disturbance and may not have much impact on the reactor momentarily performance itself, in case of continuity, it can leave... 

This thesis aims at reducing the need for labeled data in the SLU domain by the means of active Learning methods. This need is due to the lack of labeled datasets for Spoken Language Understanding (SLU) in the Persian language, and fairly high labeling costs. Active learning methods enables the learner to choose the most informative instances to be labeled and used for training, and prevents labeling uninformative or redundant instances. For modeling the SLU system, several statistical models namely MLN (Markov Logic Networks), CRF (Conditional Random Fields), HMM (Hidden Markov Model) and HVS (Hidden Vector State) were reviewed, and finally CRF was chosen for its superior performance. The... 

Integrated guidance and control (IGC) as a new approach to guidance and control methods has been studied in this thesis. A new approach to nonlinear aerodynamic formulation with backstepping controller has been proposed in order to improve interception. Various curve fitting techniques like Gram-schmidt method has been tested. But finally a planar aerodynamic formulation was used which only varies with angle of attack. Results showed that the proposed method requests smaller control input than the linear IGC formulation and conventional G&C methods, because of more precise knowledge of normal force coefficient. Thus the vehicle experiences smaller angle of attack and normal acceleration.... 

Today digital imaging systems have been widely used due to their ease of use and proper costs, but still they suffer from low contrast and resolution. Because of technical limits and expensiveness of hardware, software techniques like super resolution have been used. By super resolution we mean increasing the density of an image’s pixels. Super resolution can be categorized as “single image super resolution” and “multi-image super resolution”. Single image super resolution is applied on a low quality image which has blur and/or noise of environment and imaging system and increases its quality and density to an acceptable level. In multi-image super resolution some auxiliary images captured... 

Delay of Interconnects in modern digital ICs is several times greater than delay of gates. One proper measure for this problem is to shorten interconnects length by using three dimensional structures instead of conventional two dimensional structures. In these structures TSVs (Through Silicon Vias) make connection between stratums. Power integrity in 3D ICs necessitates power distribution networks to have minimum IR drop and Ldi/dt noise. In this dissertation we design power distribution network considering IR drop and Ldi/dt noise margin. We expand a mathematical model which represents differential equation of power distribution in the surface of each stratum. Using this expanded model we... 

This paper presents an integrated attitude control and estimation of satellite by using adaptive neural fuzzy (ANFIS) logic, indeed a system which using ANFIS controller and estimator is considered then an ANFIS simulator that can control and estimate contemporary is supposed. ANFIS system has been trained by using data obtained from an optimal PID controller. Then ANFIS controller performance has been compared with the performance of a PID controller, the analogy has repeated in different situations such as noise and uncertainty. Results show that system with ANFIS controller is more optimal than PID’s in all these situations. After that ANFIS estimator is studied and results indicate the... 

The purpose of this Thesis is designing and constructing of high voltage power supply with very low ripple. Proposed method of this thesis is formed of two sections. In this proposed structure, in first section, structure is on basis of diodes rectifier that has been used for producing main portion of output load energy. Second section uses with aim of regulating of first stage voltage. In attention to existence of noises and available offsets in different sections of proposed circuits, model is basis of two stages structure. Sampling of output voltage by using of resistance divider for main loop of circuit has been done. So noises and offsets available in circuit act as prevented factor... 

In this thesis, LMS, NLMS, RLS, ADALINE and ANFIS as five adaptive noise removal methods have been studied with a software application approach. The aim of this study is to obtain the best method to remove noise in terms of signal to noise ratio (SNR) improvement as well as the speed of convergence. In this regard, firstly by applying a frequency sweep input, which is contaminated with white noise, the performance of these algorithms are investigated. Then, an audio signal is utilized as the target input, and the performance of the corresponding algorithms have been analyzed in aspect of filter order and learning coefficient. The results show that by increasing the order of filter and... 

The aim of this project is analysis of fuselage vibration reduction on turboprop aircraft, by using passive methods. In this method by design and installation of tuned vibrant absorber (a system composed of mass and auxiliary spring) which its natural frequency is tuned, taking into account the excitation frequency of the vibrant fuselage body under harmonic force. And the motion of the point which is connected to it, would be ceased. Considering the place limitations and weight in the aircraft design, the designed absorber with respect to space and occupied volume shall be mountable on the aircraft frames and for maximum reduction of skin vibrations and eventually damping of acoustic energy... 

The emergence of online social networks (OSN) has encouraged scientists to investigate them more deeply due to availability of excessive data and increased computational power. Diffusion is a fundamental process taking place in such networks. The spread of news, ideas, influence and diseases are examples of diffusion in social networks. The importance of information diffusion in different disciplines such as economics, politics and social behavior has motivated us to study diffusion networks in this thesis. Diffusion’s behavior is strongly influenced by the underlying network in social networks. Despite this fact most research done in this area ignores the dynamics of the underlying network.... 

In the last few decades, the consumption of fossil fuels and its increasing worldwide price on one hand, and the severity of global warming on the other hand have led researchers and engineers to invent and expand new cooling technologies. Cooling has the largest portion of energy consumption of households during the hot season of a year. In addition to high energy consumption, the common cooling systems utilize gases which are harmful for environment. Thermoacoustics is a new and recent technology which has arised from combination of acoustics and thermodynamics. In Iran, research in this new field was pioneered by Ghorbanian in Department of Aerospace Engineering at Sharif University of... 

We show that the equations of reinforcement learning and light transport simulation (rendering equation) are related integral equations. Based on this correspondence, a scheme to learn importance while sampling path space is derived. The new approach is demonstrated in a consistent ray tracing algorithm that uses reinforcement learning to progressively learn where light comes from. As using this information for importance sampling includes information about visibility, too, the number of light transport paths with non-zero contribution is dramatically increased, resulting in much less noisy images within a fixed time budget  

Signal transmission of information on noiseless and lossy channels is an important issue in data transmission. Using the amplifier in the transmission channels is a good solution to help send information on longer channels. In classical communication, information can be coded in the amplitude or phase of the field and an amplifier is responsible for amplifying these parameters. If we consider the conditions ideal and ignore electrical noises, Classical mechanics does not impose any restrictions on the amplification of arbitrary classical signals. Instead, in quantum telecommunications the information encoded on the quadrature of the electromagnetic field are mounted on quantum states, such... 

Some microwave tubes can function as a narrowband power amplifier and their output power spectrum is an indicator of their amplification and efficiency. One of the factors affecting its power spectrum is the noise and ripple of its HVDC power supply. To reduce the negative effects of power supply, first there should be an exact measurement of ripple and noise in the output of the HVDC power supply. Destructive factors which affect voltage ripple measurement in the case of high DC voltage are follows as conductive interference, radiative interference, intrinsic noise of electrical elements, and nonideal frequency response of voltage divider. After identifying and suppressing the mentioned... 

In this study, the reconstruction of the neutron noise source in the core of the VVER-1000 reactor was carried out using fuzzy neural network and parallel processing of parallel process circuit design. The noise of power reactors is derived from neutron fluctuations. Which are affected by fluctuations in reactor characteristics. These oscillations can be caused by the displacement of the elements forming the core or due to changes in temperature or density and so on. It is clear that any change in the elements of a reactor will make itself a change in the corresponding to cross-section of material. These changes called as pertubation. In this project, by using neuro-fuzzy network...