Sharif Digital Repository

In this paper, we propose a new architecture for nanophotonic Networks on Chip (NoC), named 2D-HERT, which consists of optical data and control planes. The proposed data plane is built upon a new topology and all-optical switches that passively route optical data streams based on their wavelengths. Utilizing wavelength routing method, the proposed deterministic routing algorithm, and Wavelength Division Multiplexing (WDM) technique, the proposed data plane eliminates the need for optical resource reservation at the intermediate nodes. For resolving end-point contention, we propose an all-optical request-grant arbitration architecture which reduces optical losses compared to the alternative... 

We present a new method for modeling and design of photonic crystal nano-beam resonators (PCNBRs) based on cascaded transmission lines. The proposed model provides an accurate estimate of the PCNBRs properties such as resonance wavelength and quality factor (Q) with much smaller computation cost as compared to the brute-force numerical methods. Furthermore, we have developed a straightforward technique for the design of high-Q PCNBRs based on resonance modes with Gaussian electromagnetic field profiles. The results obtained by using the proposed transmission line model are compared against numerical and experimental results and the accuracy of the model is verified. The proposed model... 

The performance of an axisymmetric supersonic mixed-compression air intake has been investigated experimentally. The intake has been designed for free stream Mach number of 2.0. This study has two main goals, firstly to investigate the performance of the intake without boundary-layer bleed in design and off-design conditions and secondly to study the effects of a slot bleed on the intake performance. The intake has been tested at free stream Mach numbers of 1.8, 2.0, and 2.2 and zero degree angle of attack. Total pressure recovery (TPR), mass flow ratio (MFR) and flow distortion (FD) have been selected parameters to assess the intake performance. The bleed slot is located upstream of the... 

Objectives: The aim of this study was to investigate the effects of implant design on the apex area and on stress and stress patterns within surrounding bone. Methods: Three commercially available implants with the same diameter (3.5 mm), same length (10-11 mm), and same complement abutment were selected for modeling as follows: (1) flat apical design with light tapering degree, (2) dome-shaped apical design with light tapering, and (3) flat apical design with intense tapering in one-third of the apical area. According to human cone-beam computed tomography (CBCT), the bone was modeled using a cortical thickness of 2 mm and cancellous bone. Forces of 100 N and 300 N in the vertical and 15°... 

A methodology is developed for the design of optimum viscous fluid passive energy dissipation systems using pole assignment active control algorithm. In this method, the procedure to assign the new structural poles is slightly modified such that the resulting structural properties (i.e., the optimum locations of system poles) can be achieved merely by modification of structural stiffness and addition of a passive control system. A combination of stiffness reduction and increase of damping is utilized to reduce both acceleration and displacement response. It is shown that the control systems designed using this method provide structural performances slightly better than or close to those of... 

A method to design a tunable low noise amplifier (LNA) for multiband receivers is proposed. This paper also presents a single-ended to differential conversion (S2DC) topology which improves the LNA linearity without degrading its noise performance. Combining input tuning with S2DC in a single stage reduces power consumption of the LNA and decreases effects of supply noise. An LNA has been designed based on the proposed method for 2.3-4.8 GHz in a 0.18 μm CMOS technology. Simulations show an IIP3 of -3.2 dBm, a less than 3.7 dB noise figure (NF), a voltage gain of 24 dB in the whole frequency range. The LNA draws 13.1 mW from a 1.8 V supply. The results indicate that the proposed tuning... 

Matching diagram is a key part of the conceptual design process to determine the wing area and the required power. However, it requires drag polar estimation and the assumption of maximum lift coefficient. In case of conventional manned aircraft, early estimation techniques are based on statistical data that are not suitable for hand-launched aircraft. In this study, it has been attempted to present the performance calculations and a proper conceptual design model by acquiring sound values for the aerodynamic coefficients in low Reynolds number, using statistical wetted area as well as a raw design of fuselage, wing and tails. The process is applied to a sample scenario and the results are... 

The linear unfolding inverse finite element method (IFEM) has been modified and enhanced by implementing large deformation relations. The method is helpful to predict forming severity of the part that should be deep drawn as well as its blank shape and strain distribution in preliminary design stage. The approach deals with minimization of potential energy and large deformation relations with membrane elements. To reduce the computation time, the part is unfolded properly on the flat sheet and treated as 2D problem. Moreover, the nonlinear stress-strain relationship of plastic material properties has been considered to increase the accuracy of the results. An experiment set up has been... 

This paper deals with irrational transfer functions having monotonic nondecreasing step responses. Firstly, some results on the monotonicity of step responses in irrational transfer functions describing fractional- or distributed-order systems are presented. Then, some conditions guaranteeing the existence of monotonic nondecreasing step responses in more general forms of irrational transfer functions are found. Various examples are brought to show the usefulness of the obtained results in time response analysis of fractional/distributed-order systems. The achievements of the paper can be used in the design of control systems having monotonic step responses  

The integration of materials selection and design are essential to the success of new product development, especially when applied to biomedical devices. The knee prosthesis, like any other implant, is a product that still lacks satisfactory design solutions for solving the problem of aseptic loosening. Stress shielding is one of the main causes of aseptic loosening that is intimately related to the overall design of the knee prosthesis. The design of the location pegs in the femoral component of the knee prosthesis is seen to have a critical effect on the stress shielding. In this study, therefore, different combinations of location peg geometries and material designs were assessed using... 

In this work, two-membrane distillation (MD) modes, direct contact MD, and sweeping gas MD were investigated for synthesized and real (Persian Gulf) seawater desalination. A commercial PTFE membrane with 0.22 μm pore size was characterized (using atomic force microscopy and scanning electron microscopy) and was used for experiments. A multipurpose plate and frame MD module was used for desalination experiments. The effects of various operating conditions and MD module design, as well as feed type on the permeation flux have been studied. The feed temperature was found to be the most effective operating parameter. The flow rate in both sides of the MD module was found to be effective;... 

In general, reliability is the ability of a system to perform and maintain its functions in routine, as well as hostile or unexpected, circumstances. The Redundancy Allocation Problem (RAP) is a combinatorial problem which maximizes system reliability by discrete simultaneous selection from available components. The main purpose of this study is to develop an effective approach to solve RAP, expeditiously. In this study, the basic assumption is considering Erlang distribution density for component failure rates. Another assumption is that each subsystem can have one of cold-standby or active redundancy strategies. The RAP is a NP-Hard problem which cannot be solved in reasonable time using... 

With current memory scalability challenges, Phase Change Memory (PCM) is viewed as an attractive replacement to DRAM. The preliminary concern for PCM applicability is its limited write endurance that is highly affected by pro-cess variation in nanometer regime. This increases the vari- ation in cell lifetime resulting in early and sudden reduc- tion in main memory capacity due to wear-out of few cells. When some memory pages reach their endurance limits, other pages may be far from their limits even when using a perfect wear-leveling. Recent studies have proposed redi- rection or correction schemes to alleviate this problem, but all suffer from poor throughput or latency. On contrary, we... 

Design and control of micro robots have been one of the interesting fields in robotics in recent years. One class of these micro robots is the legged robots. Various designs of legged robots have been proposed in the literature. All designs rely on friction for locomotion. In this paper dynamic model of a planar two-legged micro robot is presented using Luger friction model, and an adaptive neural controller used to control the robot to improve robustness and velocity of the robot. As mentioned earlier, friction plays an important role in locomotion of the legged robots. However, especially in legged micro robots, it is difficult to model the frictional force correctly since environmental... 

In transition from concept design to detail design, designers and engineers need to find specific materials to optimize performance of the systems. The large number of materials and the wide range of manufacturing processes cause engineers always to seek new materials selection methods. In this research work a new method so called QFD method, which employs materials indices, is introduced. The method enjoys a combination of Ashby's materials selection concepts with the Quality Function Deployment (QFD) tool. The QFD method, which is modified here to fit the materials selection field, provides the designer with the required weighting factors for the material indices. Incorporation of House of... 

In this paper, a comprehensive model is used to describe dynamic behavior of SDA and its components during stepwise motion. In this model, Hamilton’s principle and Newton's method are used to extract dynamic equations of the SDA plate and dynamic equation for the linear motion of SDA. Comparison between the modeling results and available experimental data shows that this model is very effective in predicting some design objectives such as step size and output force for this type of actuators  

A potential peculiarity of software systems is that a large number of soft-errors are inherently derated (masked) at the software level. The rate of error-deration may depend on the type of algorithms and data structures used in the software. This paper investigates the effects of the underlying algorithms of programs on the rate of error-deration. Eight different benchmark programs were used in the study; each of them was implemented by four different algorithms, i.e. divide-and-conquer, dynamic, backtracking and branch-and-bound. About 10,000 errors were injected into each program in order to quantify and analyze the error-derating capabilities of different algorithm-designing- techniques.... 

Due to flexibility, relatively small weight and low energy-dissipative characteristics of cables, they are vulnerable to external excitations such as wind, wind-rain, earthquake and traffic loadings. Among them, galloping phenomenon is one of the most important sources of electrical/mechanical failures in power transmission lines. In this paper, tuneable vibration absorbers (TVAs) are used to suppress galloping forced vibrations (as a semi-active control approach). Using mode summation technique, mathematical model of the hybrid problem including the transmission line and an arbitrary number of absorbers is presented. Developing a sophisticated multi-loops optimization algorithm, best values... 

A 37 dBm power amplifier (PA) is designed on a 0.25 μm optical T-gate pseudomorphic high electron mobility transistor (pHEMT) technology. The design of this two-stage PA along with a step-by-step design procedure is presented in this paper. This methodology can be used for design of PA in different technologies and frequencies. The PA delivers 5 W output power over the frequency band of 13-19 GHz. It shows average power-added efficiency of 37% and large signal gain of 15 dB in measurements which is consistent with simulation results. The output power and efficiency of the realised amplifier reach maximums of 37.6 dBm and 45%, respectively. Considering output power, bandwidth, chip area and... 

A glassy carbon electrode (GCE) is modified with platinum nanoparticle (PtNPs) decorated multiwalled carbon nanotube (MWCNT). The modified electrode is applied for the determination of ceftriaxone (CFX) in the presence of lidocaine. Different methods were used to characterize the surface morphology of the modified electrode. The electrochemical behavior of CFX was investigated at GCE, MWCNT/GCE and PtNPs/MWCNT/GCE. A factorial-based response-surface methodology was used to find out the optimum conditions with minimum number of experiments. Under the optimized conditions, oxidation peak currents increased linearly with CFX concentration in the range of 0.01-10.00 μM with a detection limit of...