Sharif Digital Repository

In the investigations presented here, the feasibility of producing magnetic-nonmagnetic bimetals made of 316L/17-4PH and 316L/Fe powders by micro-metal injection moulding process (μ-MIM) was studied. In order to achieve sound replication of small specimens with dimensions less than 1 mm, very fine powders with mean particle sizes in the range of 3-7 μm were used. A wax-polymer binder system specially designed for micro-moulding was used to make up the feedstock. The isothermal and non-isothermal sintering behaviour of the moulded components was evaluated under hydrogen atmosphere. The effect of powder-binder-ratio of the feedstock, master alloy addition, and sintering conditions on the... 

Here a special state variable feedback or state feedback for short is introduced with the main objective of providing a convenient method for decoupling a MIMO transfer matrix. Decoupling in general and decoupling via state feedback in particular offer obvious advantages in the design and synthesis of controllers for MIMO systems. The early parts of this paper deal with the eigenvalues, poles, and zeros as well as the controllability and observability properties of the proposed closed-loop system as compared with those of the open-loop system. The proposed method is tested on a model of a realistic physical system and results are illustrated. © 2008 IEEE  

A circuit model based on the transmission line theory is proposed to analyze the recently introduced metal-insulator-metal (MIM) complementary split-ring resonators (CSRRs). It is shown that integer and noninteger modes of CSRRs can be characterized by transmission line models with short- and open-circuited terminals. The proposed circuit model is then extended to incorporate side-coupling effects between the CSRRs and straight MIM waveguides. Thereby, simple closed-form expressions are provided for the coupling quality factor. It is shown that waveguide resonator structures based on CSRRs at specific resonance frequency and bandwidth can be smaller than waveguide resonator structures based... 

An approximate and accurate enough multi-conductor transmission line model is developed for analysis of side-coupled metal-insulator-metal (MIM) waveguides. MIM waveguides have been already modeled by single conductor transmission lines. Here, the side coupling effects that exist between neighboring plasmonic structures are taken into account by finding appropriate values for distributed mutual inductance and mutual capacitance between every two neighboring conductors in the conventional single-conductor transmission line models. In this manner, multi-conductor transmission line models are introduced. Closed-form expressions are given for the transmission and reflection of miscellaneous MIM... 

A transmission line model is developed for coupled plasmonic metal-insulator-metal (MIM) waveguides. In the proposed model coupling between electric fields of two plasmonic waveguides is modeled by distributed mutual capacitor while distributed mutual inductor accounts for magnetic field coupling. These mutual elements are determined using propagation constants of supermodes of coupled waveguides. The model is applied to analyze coupled line directional coupler and side-coupled rectangular resonators. The effectiveness of the model is assessed using fully numerical finite-difference time-domain (FDTD) technique. The results have excellent agreement with the numerical methods  

An efficient layout technique is proposed to eliminate the effect of the bottom-plate capacitors in a C-2C Digital to Analog Converter (DAC). Using this technique, the bottom-plate capacitors of 2C capacitors in the C-2C structure are placed in parallel with 1C capacitors. Then, the effect of the bottom plate capacitors is nulled by modifying the size of the main 1C capacitors. Hence, avoiding the complexity of calibration, this technique can preclude the effect of the bottom-plate to ground capacitance. Statistical simulations prove that the proposed technique is robust to non-ideal effects such as mismatch or parasitic capacitors. A 10-bit C-2C DAC is modeled in COMSOL Multiphysics using... 

Fuzzy sliding mode control (FSMC) as a robust and intelligent nonlinear control technique is proposed to control processes with severe nonlinearity and unknown models. The performance of the proposed method has been evaluated for both single input single output (SISO) and MIMO nonlinear systems through its application in three severely nonlinear processes that are frequently used as benchmarks of nonlinear process control strategies. The evaluation shows that, despite its lack of dependence on the process model, the proposed method performs almost the same as conventional sliding mode control alternatives that utilize all the information that exists in the mathematical model of the process.... 

Waveform design for Target identification and classification in MIMO radar systems has been studied in several recent works. While the previous works considered signal independent noise and found optimal signals for an e stimation algorithm, here we extend the results to the case where clutter is also present and then we will find the optimum waveform for several estimators differing in the assumptions on the given statistics. Several different approaches to the optimal waveform design are proposed, including minimizing the error of MMSE estimator, minimizing the maximum error of the covariance shaping least square (CSLS) estimator and minimizing the MSE error of scaled least square (SLS)... 

Waveform design for Target identification and classification in MIMO radar systems has been studied in several recent works. While the previous works considered signal independent noise and found optimal signals, here we extend the results to the case where clutter is also present and then we will find the optimum waveform for MMSE estimator. Choosing optimal waveform for MMSE estimator leads to the Semidefinite programming (SDP) problem, a convex optimization problem which can be efficiently solved through numerical methods. Explicit solution is developed for this SDP problem in two cases .In the first case, target and clutter covariance matrices are jointly diagonalizable and in the second... 

Scaling transistor size to the scale of the nanometer coupled with reduction of supply voltage has made SRAMs more vulnerable to soft errors than ever before. The vulnerability has been accentuated by increased variability in device parameters. In this paper, we present an analytical model for critical charge in order to assess the soft error vulnerability of 6T SRAM cell. The model takes into account the dynamic behavior of the cell and demonstrates a simple technique to decouple the nonlinearly coupled storage nodes. Decoupling of storage nodes enables solving associated current equations to determine the critical charge for an exponential noise current. The critical charge model thus... 

This work addresses the attitude control of a satellite by applying MIMO quantitative feedback approach. The objective is to design a set of proper controllers in presence of unknown disturbances and parametric uncertainties for a nonlinear MIMO system. The physical model of satellite utilizes three reaction wheels as actuators. The controller goal is to change the rotational speed of reaction wheels to adjust the satellite in desired course. First, the mathematical model of satellite and its actuators using angular kinematics and kinetic equations is developed. Quantitative feedback theory is then applied to synthesize a set of linear controllers that deals with both nonlinearities in the... 

This paper proposes a novel method to designing an H∞ PID controller with robust stability and disturbance attenuation. This method uses particle swarm optimization algorithm to minimize a cost function subject to-norm to design robust performance PID controller. We propose two cost functions to design of a multiple-input, multiple-output (MIMO) and single-input, single-output (SISO) robust performance PID controller. We apply this method to a SISO flexible-link manipulator and a MIMO super maneuverable F18/HARV fighter aircraft system as two challenging examples to illustrate the design procedure and to verify performance of the proposed PID controller design methodology. It is shown with...