Surface-Modified Graphene for Mid-Infrared Detection

In this chapter, morphology variation and electronic structure in a surface-modified graphene are demonstrated by both calculation and experimental results. The results indicate that the band structure and morphology of modified graphene sheets are altered because of changing in the type of hybridization of carbon atoms in the graphene sheet. Accordingly, the band gap of graphene can be tuned by surface modification using organic molecules. Then, modified graphene is used for fabrication of infrared detectors. The properties of unmodified graphene photodetectors were also measured so as to compare with modified graphene photodetectors. The results demonstrate that modification of graphene using organic ligands improved the detection parameters such as fast response time, electrical stability and low dark current. Moreover, the sensitivity of photodetectors based on modified graphene was significantly improved

All-optical Semiconductor Optical Amplifiers Using Quantum Dots (Optical Pumping)

In the first portion of this chapter, a short review on all-optical processing is presented. Following the ideas of all-optical processing, a basic unit cell is introduced for the realization of these systems. To this end, an all-optical semiconductor optical amplifier based on quantum dots (QD-SOA) is presented and used as the basic unit cell. Then, a novel scheme for a high-speed all-optical half-adder based on quantum dot semiconductor optical amplifiers has been theoretically and extensively analyzed. We accelerate the gain recovery process in QD-SOA with a control pulse (CP) using the cross-gain modulation (XGM) effect in QD-SOA (based on a novel work reported by Rostami et al published in IEEE J. Quantum Electron in 2010). In this proposed scheme, a pair of input data streams simultaneously drives the switch to produce sum and carry. The proposed scheme is driven by the pair of input data streasms for one switch between which the Boolean XOR function is to be executed to produce a sum-bit. Then, one of the input data is utilized to drive the second switch and another is used as input data for it to produce a carry-bit. In the proposed structure, we need to use an optical attenuator to reduce the power level of the optical signal. Thee, data pulse is at least an order of magnitude stronger than the incoming pulse; thereforehowever, only the input pulse can alter QD-SOA’s optical properties. Also, an all-optical cross-phase modulation (XPM) wavelength converter has been utilized to obtain an all-optical AND gate, which is logic CARRY. Logic SUM and CARRY are simultaneously realized in the proposed structure. The operation of the system is evaluated and demonstrated with a Tb/s bit rate. The proposed structure is mathematically modeled by writing rate equations and then is numerically simulated with success. High-speed operation capabilities of the proposed all-optical half-adder structure are evaluated by numerical simulation

Robust Topology Optimization under Load and Geometry Uncertainties by Using New Sparse Grid Collocation Method

In this paper, a robust topology optimization method presents that insensitive to the uncertainty in geometry and applied load. Geometric uncertainty can be introduced in the manufacturing variability. Applied load uncertainty is occurring in magnitude and angle of force. These uncertainties can be modeled as a random field. A memory-less transformation of random fields used to random variation modeling. The Adaptive Sparse Grid Collocation (ASGC) method combined with the uncertainty models provides robust designs by utilizing already developed deterministic solvers. The proposed algorithm provides a computationally cheap alternative to previously introduced stochastic optimization methods based on Monte Carlo sampling by using the adaptive sparse grid method. Numerical examples, such as a 2D simply supported beam and cantilever beam as benchmark problems, are used to show the effectiveness and superiority of the ASGC method

Implementation of Strategic Plans in Municipalities (Case Study: Tabriz Municipality)

Strategic plan divides the internal affairs of the organization to financial perspectives, customer perspective, internal processes and learning and growth perspective and determines their governing relations in a certain context. The purpose of this study is to implement the strategic plan in the Municipality of Tabriz, District 1. The used methodology is practical descriptive analysis. The results of the research findings show that implementation of strategic plans in Tabriz Municipality improves the performance of that institution