Sharif Digital Repository

Hereby a simple, low-cost and scalable route is being presented for preparation of binder-free electrodes of reduced graphene oxide (RGO) on Ni foam (Ni/Gr). In this regard, the Ni foams are dipped in graphene oxide (GO) slurry. Next, the GO loaded Ni foams are kept in a freeze dryer for 24 h and heated up to 800 °C in an inert atmosphere. In this approach, the amount of active materials can be easily optimized for capacitive deionization (CDI). The characterization of Ni/Gr electrodes revealed a 3D porous assembly of RGO on Ni substrate which is helpful for the fast ion diffusion and rapid electron transport. The electrochemical performance of the prepared electrodes is investigated in both... 

In this study, a thorough analysis of image reconstruction in an active millimetre-wave (MMW) cylindrical imaging system is performed. To improve the system's performance in terms of the total cost as well as the coupling effect, sparse multistatic arrays are desired. Nevertheless, the existing reconstruction methods fail to operate in sparse multi-static antenna-array systems. Therefore, to address these shortcomings, in this study, at first, the existing MMW mono-static cylindrical image reconstruction methods are modified in both single-frequency and wideband reconstruction platforms. Moreover, in order to further improve the image quality and the system cost, a sparse multi-static... 

Asynchronous data fusion is inevitable in track-to-track fusion for tracking high-speed targets. For low-speed targets, e.g., the movement of clouds, synchronization is insignificant and, depending on the application, may be disregarded. Real-time asynchronous fusion is a demanding task in sensor networks when the sensors are not synchronous in sampling-rate or in sampling-phase. In the method proposed in this paper, an estimator in the fusion center estimates the actual time of the sample with respect to the time-reference of the fusion center upon receiving the data from a sensor. Then, the computer of the fusion center uses predictions to transfer all the received data to the data... 

By the advancement in technology on one side, and governmental as well as social demands for lowest rate of driving accidents and reliable communication among vehicles on the other side, particularly in highways, vehicular ad-hoc networks (VANETs) are of special interest as a reliable approach to this aim. VANET is typically defined as the communication network for wireless communicating between vehicles in a region. One of the most important challenges in such networks is reliable routing of data packages among the vehicle users. Several VANET routing topologies are published in the literature; however, there is still a lack of reliable scheme. This is due to the nature of users behaviour... 

This paper addresses the problem of optimal power allocation in multiuser OFDM ad-hoc networks. Our objective is to maximize the weighted rate-sum of users under total transmit power constraint. Maximizing a weighted rate-sum is more amenable whereas appropriate weight assignment to different users, guarantees fairness among users. We propose a distributed algorithm for optimal power allocation based on reaching a consensus among users for power allocation. The proposed algorithm is tractable in the sense of computational complexity and requires only local information at each node. Simulation results and the analysis of the algorithm are presented to support the proposed idea. © 2006 IEEE  

The authors regret We have found, there is a problem with the image orders in the last version of the article that is being published online. In the accessible version, the caption of the images are exactly in the true orders, but the images are shifted up and they are not shown in their exact positions. This Corrigendumm is being released for revision of the image orders, like what they were in the accepted version of the manuscript. The materials are shown in the following pages. The authors would like to apologise for any inconvenience caused. [Formula presented] Scheme 1. Binder-free fabrications of the PPOGrCNT on nickel foam (Ni/PPOGrCNT electrode). [Formula presented] Fig. 1. (a)... 

In this paper, by applying a new permutation to the full-diversity block circular delay diversity (BCDD) space-frequency codes (SFCs), we show that their performance could be enhanced. Furthermore, we propose a new method for performing the permutation in the absence of partial channel state information at the transmitter. This new permutation, which is done based on artificial delay and power profiles (ADPPs), could improve the performance of the BCDD SFCs more than 3 dB as simulation results demonstrate  

A joint theoretical and experimental study of the kinetic and mechanism of the rearrangement of allyl p-tolyl ether was performed in order to study the kinetic and mechanism of the reaction. Experimental studies were performed in gas phase over a temperature range of 493.15-533.15 K. The experimental Arrhenius parameters of this reaction were measured to be Ea = 36.08 kcal mol-1, ΔS# = -7.88 cal mol-1 K-1, and Log A = 11.74, experimentally. Using GC for the mixture of the reaction with and without cyclohexene demonstrated that the reaction is clean without any radical intermediates. The experimental results show that the studied reaction is unimolecular and proceeds through a concerted... 

Polyphosphate reduced graphene oxide on Ni foam (PPO-RGO/NF) is synthesized by varying weight ratios of Na5P3O10 (PO): graphene oxide (GO) with a simple, scalable and low cost method through freeze-drying of the PO-GO/NF followed by thermal treatment of the prepared electrodes. The resulting samples are characterized using scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), transmission electron microscopy (TEM), fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), Brunauer-Emmett-Teller (BET), and raman spectroscopy methods. The results show that the weight ratio of PO:GO, considerably affect the... 

Inverse method and artificial neural network were employed in modeling the rheological behavior of the AZ61 Mg alloy. The hot deformation behavior of these alloys was investigated by compression tests in the temperature range 250-350 °C and strain rate range 0.0005-0.1 s-1. Investigation of stress-strain curves and microstructure of the compression specimen illustrate occurrence of dynamic recrystallization. To determining parameters of two suggested constitutive equations global optimization technique, genetic algorithm, was used. The predicted results by inverse method and ANN depicted a good agreement with the experimental data even if the ANN results has shown the best predicted... 

We show that in the family of degree d⩾ 2 rational maps of the Riemann sphere, the closure of strictly postcritically finite maps contains a (relatively) Baire generic subset of maps displaying maximal non-statistical behavior: for a map f in this generic subset, the set of accumulation points of the sequence of empirical measures of almost every point in the phase space, is equal to the largest possible one, that is the set of all f-invariant measures. We also introduce an abstract setting to study non-statistical dynamics and sufficient conditions for their existence in a general family of maps. These sufficient conditions are related to the notions of “statistical instability” and... 

An efficient and commercially available method is introduced for preparation of a binder-free electrode for capacitive deionization (CDI) application. An interconnected porous composite consisting of polyphosphate (PPO), graphene (Gr) and multi-walled carbon nanotube (CNT) is fabricated and assembled on a Ni foam substrate to prepare a binder-free electrode (Ni/PPOGrCNT). The resulting electrodes were characterized using various instrumental techniques such as TEM, SEM, EDS, XRD, FT-IR, Raman, XPS and XRF. Characterization results indicated that a mesoporous PPO structure is formed on a 3D assembly of carbon backbone. Accordingly, the 3-D porous structure facilitates the ion diffusion into... 

In this study, the authors show that the coding advantage (CA) of quasi-orthogonal space-frequency block codes (QOSFBCs) could be decomposed into two parts, namely intrinsic CA (ICA) and extrinsic CA (ECA). Then, by using the ICA, the authors demonstrate that the optimum precoder of the QOSFBCs could be analytically derived without any requirement of the exhaustive search. Then, by improving the ECA, the authors enhance performances of the QOSFBCs efficiently - up to 4dB. Finally, the authors show that a very fast optimisation process for the QOSFBCs is viable over any arbitrary frequency-selective channel  

In this paper we consider the issue of energy efficiency in random access networks and show that optimizing transmission probabilities of nodes can enhance network performance in terms of energy consumption and fairness. First, we propose a heuristic power control method that improves throughput, and then we model the Utility Constrained Energy Minimization (UCEM) problem in which the utility constraint takes into account single and multi node performance. UCEM is modeled as a convex optimization problem and Sequential Quadratic Programming (SQP) is used to find optimal transmission probabilities. Numerical results show that our method can achieve fairness, reduce energy consumption and... 

This paper introduces adaptive consensus, a spatio-temporal adaptive method to improve convergence behavior of the current consensus fusion schemes. This is achieved by introducing a time adaptive weighting method for updating each sensor data in each iteration. Adaptive consensus method will improve node convergence rate, average convergence rate and the variance of error over the network. A mathematical formulation of the method according to the adaptive filter theory as well as derivation of the time adaptive weights and convergence conditions are presented. The analytical results are verified by simulation as well. ©2006 IEEE  

In this letter, both the number of participating nodes and spatial dispersion are incorporated to establish a bi-objective optimization problem for maximizing the quality of aggregation under interference and delay constraints in tree-based wireless sensor networks (WSNs). The formulated problem is proved to be NP-hard with respect to Weighted-sum scalarization and a distributed heuristic aggregation scheduling algorithm, named SDMAX, is proposed. Simulation results show that SDMAX not only gives a close approximation of the Pareto-optimal solution, but also outperforms the best, to our knowledge, existing alternative proposed so far in the literature  

A joint theoretical and experimental study of the kinetic and mechanism of the rearrangement of allyl p-tolyl ether was performed in order to study the kinetic and mechanism of the reaction. Experimental studies were performed in gas phase over a temperature range of 493.15–533.15 K. The experimental Arrhenius parameters of this reaction were measured to be Ea = 36.08 kcal mol−1, ΔS# = −7.88 cal mol−1 K−1, and Log A = 11.74, experimentally. Using GC for the mixture of the reaction with and without cyclohexene demonstrated that the reaction is clean without any radical intermediates. The experimental results show that the studied reaction is unimolecular and proceeds through a concerted...