Sharif Digital Repository

In this paper, different models of gain enhanced amplifier are compared and the most accurate one is chosen. Based on this model, complete symbolic small signal analysis is performed and a design procedure leading to high speed gain boosted amplifier is presented  

This paper deals with the possibilities of cancellation of unwanted signals by steering nulls of the pattern in the direction of arrival of signal while keeping the main beam to the desired direction. New iterative adaptive digital beam forming technique is presented here to enhance the conventional effectiveness of beam forming in common commercial application. Simulation and measurement results confirm that this algorithm can achieve effective Co-Channel Interference (CCI) suppression, while increasing the strength of the desired signal  

A new level converter for use in dual voltage SOI digital circuits is presented. The technique which uses the idea of keeper transistors, consumes less power compared to the traditional methods. The effects of load capacitance on the circuit are studied by extensive simulations  

This paper presents a new method to counter Anti Radiation Missile (ARM) threats, which is effective against advanced ARM. By using random phase and amplitude active decoys in the specified optimum positions and network implementation we show that ARM threats will be removed profoundly. Also, iterative methods are presented to cancel the internal interference effects in the proposed structure  

Adapting natural phenomena rendering for realtime applications has become a common practice in computer graphics.We propose a GPU-based multi-band method for optimized synthesis of "far from coast" ocean waves using an empirical Fourier domain model. Instead of performing two independent syntheses for low- and high-band frequencies of ocean waves, we perform only low-band synthesis and employ results to reproduce high frequency details of ocean surface by an optimized iterative up-sampling stage. Our experimental results show that this approach greatly improves the performance of original multi-band synthesis while maintaining image quality. © Springer-Verlag 2009  

In this paper, we study three types of jammers, namely, pulse-jammer, partial-band jammer, and follower-jammer, in a typical fiber-optic-based spectrally phase-encoded optical code division multiple-access (SPE-OCDMA) system. We analyze, mathematically, the effects of the aforementioned jammers on the performance of an SPE-OCDMA system for two scenarios, namely, ideal noiseless channel with an ideal optimum receiver and an ultrahigh-speed nonlinear receiver based on two-photon-absorption (TPA) in a noisy channel. Also, for each of the above cases, two types of modulation, namely, on-off keying (OOK) and two-code keying (2CK) are investigated and their system performances are compared. It is... 

In this study, the authors perform a complete survey on S-parameter method applications to compensate the coupling effect in circular arrays. The authors illustrate that, despite the simplicity and ease of measurements, the S-parameter algorithm has an adequate performance in comparison with the external calibration techniques in real environments. Based on the simulation and experimental results, for unmatched arrays and low-frequency applications [e.g. high-frequency (HF) radars], the S-parameter method performance is demonstrated to be comparable in accuracy to the external calibration techniques. Despite multipath effect and structural scattering, the direction of arrival can be... 

For direction of arrival (DOA) estimation in compact arrays, a new approach based on time delay and amplitude estimation is presented for a known signal. The DOA can be accurately estimated without any calibration sources since the mutual coupling and multipath effects can be eliminated by the inherent mechanism of the proposed algorithm. The algorithm has significantly lower error and much less computational burden compared with the previous methods in high signal-to-noise ratio (SNR) conditions  

In this paper, we study three types of jammers, namely, pulse-jammer, partial-band jammer, and follower-jammer, in a typical fiber-optic-based spectrally phase-encoded optical code division multiple-access (SPE-OCDMA) system. We analyze, mathematically, the effects of the aforementioned jammers on the performance of an SPE-OCDMA system for two scenarios, namely, ideal noiseless channel with an ideal optimum receiver and an ultrahigh-speed nonlinear receiver based on two-photon-absorption (TPA) in a noisy channel. Also, for each of the above cases, two types of modulation, namely, ON-OFF keying (OOK) and two-code keying (2CK) are investigated and their system performances are compared. It is... 

Landslide events are among natural hazards with many fatalities and financial losses. Studies demonstrate that natural factors such as rainfall and human activities such as deforestation are important causes of triggering a landslide. In this study, an integrated two-dimensional slope stability model, SSHV-2D, is developed that considers various aspects of hydrological effects and vegetation impacts on the stability of slopes. The rainfall infiltration and water uptake of roots change the water content of the unsaturated zone. The temporal and spatial distribution of water content is estimated in the hydrological unit of the developed model. The vegetation unit of the model considers... 

Although, enhanced security is often mentioned as a noticeable benefit of Spectrally Phase Encoded Optical CDMA (SPE-OCDMA) systems, the quantity and degree of security enhancement is not considered deeply in the literature. One of the facts in determining the degree of security is to assess the resistance capability of the system against various jammers attacks. In this paper, we introduce and model three types of jammers, namely (Pulse Jammer, Partialband Jammer, and Follower Jammer). We mathematically analyze the effects of the above jammers on the performance of the SPE-OCDMA systems that use On-Off keying (OOK) modulation scheme. It is demonstrated that under certain conditions, the... 

In this paper, a new software is introduced that is developed to give the most appropriate solution for the component selection and design of a hybrid electric bus. There are several simulation programs that can simulate behavior of a hybrid electric bus, but most of them are not able to suggest the best design and the best choice of the components. Customer requirements are dissimilar and there are several different parameters that they may need. Cost, pollution, driving cycle, battery type, DC link voltage, weight, volume, fuel consumption, and acceleration are some parameters that vary from one customer to the other. The stated software that is developed and presented by this paper will... 

In this paper, sliding-mode control (SMC) is applied to a z-source converter to control output dc voltage of impedance network. The converter is assumed working in continuous conduction mode (CCM). First a comprehensive review of the literature for z-source inverter (ZSI) and use of sliding mode control in switched converters are performed. The procedure of SMC design used in ZSI is presented. The simulations for the application of SMC in z-source inverter are made and the results are illustrated. The results verify the effectiveness and robustness of the controller. © 2008 IEEE  

Lightweight aggregate is commonly used to reduce the self-weight of concrete elements which can efficiently mitigate the environmental impact. This study investigates the mechanical performance of normal weight aggregate concrete (NWAC) and Lightweight aggregate concrete (LWAC) exposed to high temperature, focusing on developing a predictive model for the stress-strain relationship of the LWAC based on the property of cement, silica fume, light weight aggregate and water/cement ratio. Mechanical properties of 30 different mixtures, including uniaxial compressive stress–strain relationship, compressive strength, modulus of elasticity, and failure strain are determined before and after high...