Sharif Digital Repository

Considering electronic skin applications, a pressure sensor based on periodic structure of graphene oxide-reduced graphene oxide (GO-rGO) has been designed and fabricated based on a low cost direct laser writing technique by utilizing the laser diode of DVD drive's pickup head. The optimization of sensor structure has been performed using computational modelling through Finite Element Method (FEM) in the COMSOL environment. The optimized structure is fabricated based on the deposition of thin layer of GO on the surface of Kapton and the pattering is performed by laser irradiation. The fabricated sensor structure has been characterized structurally and functionally. The results show that the... 

Nonlinear behavior of jacket platforms is important in both design and rehabilitation issues that depends on the bracing arrangement. Both ductility and strength of the structures derived from pushover analysis are highly related to configuration of the braces. Considering a suitable criterion such as constant weight or constant stiffness and period of the structure in all arrangement cases, one can compare the capacity curves and find the best configuration. In this paper a simple logical method for investigating the strength and ductility of the jacket structure is presented, it is shown that global geometry and configuration of the braces are very important and effective in both strength... 

Microchannels are at the fore front of today's cooling technologies. They are widely being considered for cooling of electronic devices and in micro heat exchanger systems due to their ease of manufacture. One issue which arises in the use of microchannels is related to the small length scale of the channel or channel cross-section. In this work, the maximum heat transfer and the optimum geometry for a given pressure loss have been calculated for forced convective heat transfer in microchannels of various cross-section having finite volume for laminar flow conditions. Solutions are presented for 10 different channel cross sections, namely parallel plate channel, circular duct, rectangular... 

In this paper the problem of k out of n detection, between sequence of M random bits is addressed. The main application of the result is in a radar system, when we want to detect a target (with unknown time of arrival (TOA)), using binary integration. Another application is in ESM systems, when the system wants to detect the existence of a swept jammer or a gated noise jammer. But as any other mathematical problem, it may have some other applications. In this paper some simple equations for P fa and P d calculation of a detector which detects the existence of sequence of n ones between M random bits, is derived. These equations are then used to find the optimal detector structure in some... 

In this paper, the optimal trade-off between control structures and achievable closed-loop performance is addressed. Incorporation of sparsity promoting regularization terms to the primary objective function is a well-suited approach in feature selection and compressed sensing. By the evolving role of distributed and large-scale applications, modern optimal control problems have been equipped with regularization tools as well. However, the system dynamics and convex/nonconvex constraints in optimal control framework limits the effectiveness and applicability of regularization, enforce iterative or non-convex heuristics, and pose extensive exploration. In fact, available regularized feedback... 

This paper presents a new optimization-based approach to determine the class of stabilizing control structures with the necessary set of feedback links for interconnected systems. The proposed approach relies on a graph theoretic interpretation and its equivalence in terms of binary linear programs (BLP). To carry out the primary goal, first, the stabilizability of an LTI system under the decentralized control structure is presented in terms of a BLP. Next, two graph-based criteria are proposed to characterize stabilizing control structures with the required feedback links. Finally, all possible stabilizing control structures with the necessary feedback links are derived via solving a set of... 

A coding scheme for transmission of a bit maps a given bit to a sequence of channel inputs (called the codeword associated with the transmitted bit). In this paper, we study the problem of designing the best code for a discrete Poisson channel with memory (under peak-power and total-power constraints). The outputs of a discrete Poisson channel with memory are Poisson distributed random variables with a mean comprising of a fixed additive noise and a linear combination of past input symbols. Assuming a maximum-likelihood (ML) decoder, we search for a codebook that has the smallest possible error probability. This problem is challenging because error probability of a code does not have a... 

A coding scheme for transmission of a bit maps a given bit to a sequence of channel inputs (called the codeword associated to the transmitted bit). In this paper, we study the problem of designing the best code for a discrete Poisson channel with memory (under peak-power and total-power constraints). The outputs of a discrete Poisson channel with memory are Poisson distributed random variables with a mean comprising a fixed additive noise and a linear combination of past input symbols. Assuming a maximum-likelihood (ML) decoder, we find the best codebook design by minimizing the error probability of the decoder over all codebooks. For the case of having only a total-power constraint, the... 

A coding scheme for transmission of a bit maps a given bit to a sequence of channel inputs (called the codeword associated with the transmitted bit). In this paper, we study the problem of designing the best code for a discrete Poisson channel with memory (under peak-power and total-power constraints). The outputs of a discrete Poisson channel with memory are Poisson distributed random variables with a mean comprising of a fixed additive noise and a linear combination of past input symbols. Assuming a maximum-likelihood (ML) decoder, we search for a codebook that has the smallest possible error probability. This problem is challenging because error probability of a code does not have a... 

A coding scheme for transmission of a bit maps a given bit to a sequence of channel inputs (called the codeword associated to the transmitted bit). In this paper, we study the problem of designing the best code for a discrete Poisson channel with memory (under peak-power and total-power constraints). The outputs of a discrete Poisson channel with memory are Poisson distributed random variables with a mean comprising a fixed additive noise and a linear combination of past input symbols. Assuming a maximum-likelihood (ML) decoder, we find the best codebook design by minimizing the error probability of the decoder over all codebooks. For the case of having only a total-power constraint, the... 

This paper develops a novel insight and procedure that includes a variety of algorithms for finding the best solution in a structured multi-agent system with internal communications and a global purpose. In other words, it finds the optimal communication structure among agents and the optimal policy in this structure. First, a unique reinforcement learning algorithm is proposed to find the optimal policy of each agent in a fixed structure with non-linear function approximators like artificial neural networks (ANN) and with eligibility traces. Secondly, a mechanism is presented to perform self-organization based on the information of the learned policy. Finally, an algorithm that can discover... 

This article presents a new optimization-based approach to determine the class of stabilizing control structures with the necessary set of feedback links for interconnected systems. The proposed approach relies on a graph-theoretic interpretation and its equivalence in terms of binary linear programs (BLPs). To carry out the primary goal, first, the stabilizability of a linear time-invariant (LTI) system under the decentralized control structure is presented in terms of a BLP. Next, two graph-based criteria are proposed to characterize stabilizing control structures with the required feedback links. Finally, all possible stabilizing control structures with the necessary feedback links are... 

The optimum design of reinforced concrete cantilever retaining walls subjected to seismic loads is an extremely important challenge in structural and geotechnical engineering, especially in seismic zones. This study proposes an adaptive sperm swarm optimization algorithm (ASSO) for economic design of retaining structure under static and seismic loading. The proposed ASSO algorithm utilizes a time-varying velocity damping factor to provide a fine balance between the explorative and exploitative behavior of the original method. In addition, the new method considers a reasonable velocity limitation to avoid the divergence of the sperm movement. The proposed algorithm is benchmarked with a set... 

In this research, the electromagnetic stirring (EMS) process was used to produce semi-solid slurry with globular structure from cast A356 aluminum alloy. Then the slurry was forged in a die, which named rheoforging process. Utilizing multidirectional forging (MDF), the effect of severe plastic deformation on microstructure and mechanical properties of this alloy in dendritic and globular states was investigated. Shear punch, micro- and macro-hardness tests were used to study the mechanical properties of these samples. For metallographic examinations, the optical microscope equipped with the Clemex ® image analyzer software was used. Optimum globular structure of rheoforged specimens was... 

A new di-manganese complex with "back-to-back" 1,4-bis(2,2′:6,2′′-terpyridin-4′-yl) benzene ligation has been synthesized and characterised by a variety of techniques. The back-to-back ligation presents a novel new mononuclear manganese catalytic centre that functions as a heterogeneous catalysis for the evolution of oxygen in the presence of an exogenous oxidant. We discuss the synthesis and spectroscopic characterizations of this complex and propose a mechanism for oxygen evolution activity of the compound in the presence of oxone. The di-manganese complex also shows efficient and selective catalytic oxidation of sulfides in the presence of H2O2. Density functional theory calculations were... 

The aeroelastic design of composite wings modeled as thin-walled beams is investigated through the use of curvilinear fiber. The structural model considers non-classical effects such as transverse shear, warping restraint, rotary inertia, nonuniform torsional model and also aerodynamic loads based on Wagner's function. In this paper, a linear spanwise variation of the fiber orientation resulting in a variable-stiffness structure is used to optimize the wing for maximum aeroelastic instability speed purpose, while manufacturing constraints are incorporated. Numerical results indicate improvements of aeroelastic stability of variable-stiffness wings over conventional, constant-stiffness ones  

The objective of this work is making comparison between thermodynamic models and data-driven techniques accuracy in prediction of hydrate formation pressure as a function of temperature and composition of gas mixtures. The Peng-Robinson (PR) and Patel-Teja (PT) equations of state are used for thermodynamic modeling and Artificial Neural Networks (ANNs) and Adaptive Neuro-Fuzzy Inference System (ANFIS) are used as data-driven models. The capability of each method is evaluated by comparison with the experimental data collected from literature. It is shown that there is a good agreement between thermodynamic modeling and the experimental data in most of the cases; however, the prediction...