Sharif Digital Repository

In this brief, we use the alpha power law model for MOS devices to reach a more accurate modeling of CMOS buffers in very deep submicrometer technologies. We derive alpha model parameters of a CMOS buffer for 90-, 65-, and 45-nm technologies using HSPICE simulations. By analytical efforts we find the output resistance of a minimum-size buffer and compare it with those extracted from HSPICE simulations. We propose a new model for the output resistance of a given-size buffer in any technology, which demonstrates 3% error on average as opposed to the conventional model. Also a new buffer resistance is proposed analytically and numerically to calculate the crosstalk for interconnect analysis... 

The effect of bulging of domain wall (DW) on the magnetoresistance (MR) is investigated. With taking into account the auto-correlation between the points of the interface, one can formulate the mobility within the relaxation time approximation scheme. The results show that the bulging of DW, evaluated with the commonly accepted magnetic parameters for typical ferromagnetic materials of Co, Fe and Ni, has a countable role into the MR  

In this paper, acoustic energy harvesting using a tunable Helmholtz Resonator (HR) is investigated. The frequency of resonator can be changed by varying the radial force in a membrane which is used in one of its face. Applying acoustic pressure, vibrates the air inside HR neck and therefore changes pressure in HR chamber which results in membrane vibration. Attached magnet to the membrane will vibrate and its relative motion to a fixed coil generates voltage on the basis of Faraday's law of induction. Modeling approach is developed considering equivalent nonlinear membrane stiffness and coupling of electrical circuit and mechanical device. At the end, system behavior is studied numerically... 

A double-layer SnO2/ZnO gas sensor was produced by utilisation of SnOSUB align=right2 and ZnO thin films. Top layer consisted of SnOSUB align=right2 produced by a sol gel-controlled annealing technique. Bottom coating consisted of ZnO thin film precipitated by Two-Stage Chemical Deposition (TSCD) from an aqueous zinc-containing solution. Both top and bottom coatings were analysed by SEM, XRD, EDAX and AAS. Gas sensitivity of the SnO2/ZnO double layer was determined by electrical resistance measurements. Although sensitivity was slightly reduced by double-layer formation, selectivity and stability were considerably improved by combination of the two thin layers. The existence of an... 

Metal-oxide gas sensors are widely used for detection of detrimental H2S gas. Among them, SnO2-CuO system has been proved to be an excellent candidate. The previous theoretical 2D thin bilayer model was able to explain some aspects of H2S sensing performance of this promising system. However, experimental researches have indicated that response values for this system are very diverse and various SnO2-CuO multicomponent heterostructures such as rods, wires and particles have much higher response than their thin bilayer counterparts. Understanding the reason behind this differences would help fabrication of optimized sensor element. However, the previous model cannot address this issue mainly... 

Induction motor parameter estimation is generally needed for such purposes as fault detection and the achievement of high dynamic performance drives. This paper is an attempt to use variable structure control (VSC) methodology for the on-line estimation of several significant mechanical and electrical induction motor parameters. The estimated parameters are rotor resistance, magnetizing inductance, stator resistance and viscous damping coefficient In this combined control/estimation method, we propose to apply field-oriented control to the non-linear model of induction motor, and then transform the model by Input-state linearization into canonical form. Application of variable structure... 

The present paper discusses the possibility of adding recycled polymer fibres to high performance concrete (HPC). Fibres used in this study were recovered from discarded car timing belts. To investigate different characteristics of the concrete specimens several destructive and non-destructive tests, such as compressive strength, modulus of rupture, flexural toughness, ultrasonic velocity and electrical resistance tests were carried out. In addition, slump flow tests were conducted on the fresh concrete. Experimental results from the study showed that the use of low percentages (up to 0.5%) of waste fibres improved the modulus of rupture and flexural toughness. Based on ultrasonic and... 

Upset resistance dissimilar welding of aluminium and copper narrow rods was performed. Effect of the interface characteristics was studied on the joint mechanical and electrical properties. Upset resistance welding (URW) was successful for production of joints with high strength and electrical conductivity between aluminium and copper rods. Reaction layer at the joint interface was composed of the Al2Cu cellular phase and lamellar eutectic structure of α-Al and Al2Cu. Enhancement of the welding current and decrease in the upset force increased the reaction layer thickness and strength of the joint. URW had no significant detrimental effect on the electrical conductivity of the weld zone.... 

Recent uses of intelligent composites in biomedical appliances aggrandize the necessity of bonding-strength improvement in NiTi/silicone matrix interface. SEM micrographs and pull-out tests are employed to determine the strength of the NiTi/silicone bonds in a flexible composite piece. Greater adhesion strengths are obtained due to the presence of thin oxide layer, surface roughness and frictional forces between the embedded-wires and the contacting phase. Effect of curing treatment on phase transformation temperatures of the wires is determined by electrical resistivity (ER) measurements. Results show that the curing treatment shifts the transition points of the wires towards higher... 

During recent years, many investigations have been carried out to determine how to select different materials for the making of Micro Electro Mechanical Systems (MEMS) and bio-MEMS. The NiTi shape memory alloy thin film has been much regarded as a promising candidate for MEMS due. to its unique shape memory effect and high energy output. In this research, NiTi thin film was fabricated using a sputtering technique from separate elemental Ni and Ti targets. The characterizations of the deposited films were, investigated using different analysis techniques, such as Field Emission SEM, DSC, XR.D, electrical resistivity measurement and nanoindentation. © Sharif University of Technology, June 2009... 

Nowadays, thin films have many applications in every field. So, in order to improve the performance of thin film devices, it is necessary to characterize their mechanical as well as electrical properties. In this research work we focus on the development of a model for the analysis of the mechanical and electrical properties of silver nanoparticles deposited on silicon substrates. The model consists of inter-particle diffusion modeling and finite element analysis. In this study, through the simulation of the sintering process, it is shown that how the geometry, density, and electrical resistance of the thin film layer are changed with sintering conditions. The model is also used to... 

In common catamaran vessels, demihulls are parallel to each other. In this paper, the total resistance of a catamaran vessel with non-parallel demihulls is investigated experimentally and numerically. Experiments are carried out at different Separation Ratios (S.R.), that is the ratio of fore to aft separation of the catamaran demihullsand also in two ratios of length to separation in amidships (L/Sm). The FLUENT solver, based on the Finite Volume Method (FVM), was used for numerical solution. Applying the VOF model, the free surface around the catamaran vessel and total resistance are calculated and compared with experimental results. Finally, the frictional resistance of the catamaran from... 

In this paper, we propose a circuit model for two-dimensional arrays of metallic square holes located on a homogeneous substrate, in order to propose a new scheme containing this type of metamaterials to obtain transparent electrodes with simultaneous terahertz transparency and low electrical resistance. The results of the introduced circuit model, which is a fully analytical model with explicit expressions, are in almost complete agreement with the full-wave simulations. Thanks to this analytical model, we can employ standard binomial matching transformer in order to minimize the reflected power from the structure at a desired frequency. Furthermore, taking advantage of this model, we... 

Theoretical stability analysis of broadband cascode amplifiers at high frequencies is presented. The stability of the amplifier in the presence of parasitic inductive components is thoroughly investigated. It is shown that the stability can be improved by inserting a series resistance in the gate of common-gate device of the cascode amplifier. To ensure stability, the gate resistance should be selected within specific ranges that are derived analytically. Based on the insights provided by the analyses, several practical design guidelines are given to improve the stability of high-frequency broadband cascode amplifiers. Finally, the derived results are adopted in stabilisation of an X-band...