Sharif Digital Repository

Synthesis of dithiocarbamates by the one-pot three-component Markovnikov addition reaction of an amine, carbon disulfide and an alkyl vinyl ether or N-vinylpyrrolidone is reported in polyethylene glycol (PEG) under a mild and green procedure with high yields and completely regiospecific. Also, the products were used as efficient starting materials for amidoalkylation of electron-rich arenes such as naphthols and indoles  

Scheduling sports leagues has drawn significant attention to itself in recent years, as it involves considerable revenue as well as challenging combinatorial optimization problems. A particular class of these problems is the Traveling Tournament Problem (TTP) which focuses on minimizing the total traveling distance for teams. In this paper, an efficient simulated annealing approach is presented for TTP which applies two simultaneous and disparate models for the problem in order to search the solutions space more effectively. Also, a computationally efficient modified greedy scheme is proposed for constructing a favorable initial solution for the simulated annealing algorithm. Our... 

Time-frequency and time-scale transforms are one of the powerful mathematical methods for feature extraction of non-stationary signals such as partial discharge (PD) signals. Modified Fourier-based transforms and Wavelet transforms are well known among them. PD signals can be analyzed by these influential methods but normally with some serious limitations and inadequacies. This paper proposes a new approach based on Wavelet-Hilbert transform for the analysis of electrical PD signals. The mathematical model of a Wavelet-Hilbert transform is described. Contemplating of natural behavior of PD, that is, stochastic and non-stationary an artificial multi-source of PD is simulated in a Detail model... 

Deep eutectic solvents (DESs), surmised as "the organic reaction medium of the century", have reverberated a new symphony throughout the present green millennium. A brief historical account of the DES systems and their physicochemical properties as task-specific and designer solvents for cross-coupling reactions are appraised including the hole theory that explains the underlying mechanistic pathway for this emerging neoteric medium. The insights into cross-coupling reactions and their applications are included, highlighting the significant achievements pertaining to the dual role of DESs as a solvent and catalyst. In addition, popular "name-reactions"for the carbon-carbon and... 

Gene therapy has emerged as a promising tool for treating different intractable diseases, particularly cancer or even viral diseases such as COVID-19 (coronavirus disease 2019). In this context, various non-viral gene carriers are being explored to transfer DNA or RNA sequences into target cells. Here, we review the applications of the naturally occurring amino acid histidine in the delivery of nucleic acids into cells. The biocompatibility of histidine-enhanced gene delivery systems has encouraged their wider use in gene therapy. Histidine-based gene carriers can involve the modification of peptides, dendrimers, lipids or nanocomposites. Several linear polymers, such as polyethylenimine,... 

Purpose: The nanofluid flow and heat transfer within a heat exchanger, with different thermal arrangements of internal active bodies, are investigated. Design/methodology/approach: For the numerical simulations, the lattice Boltzmann method is utilized. The KKL model is used to predict the dynamic viscosity of CuO-water nanofluid. Furthermore, the Brownian method is taken account using this model. The influence of shapes of nanoparticles on the heat transfer performance is considered. Findings: The results show that the platelet nanoparticles render higher average Nusselt number showing better heat transfer performance. In order to perform comprehensive analysis, the heatline visualization,... 

The numerical modeling of natural convection fluid flow and heat transfer in a quarter of gearwheel-shaped heat exchanger is carried out. The heat exchanger is included with internal active square bodies. These bodies have hot and cold temperatures with different thermal arrangements. Three different thermal arrangements are considered and showed with Case A, Case B and Case C. The CuO-water nanofluid is selected as operating fluid. The Koo-Kleinstreuer-Li (KKL) correlation is utilized to estimate the dynamic viscosity and thermal conductivity. In addition, the shapes of nanoparticles are taken account in the analysis. The Rayleigh number, nanoparticle concentration and thermal arrangements... 

In this study, the authors introduce an efficient secure channel coding (joint cryptography-channel coding) scheme based on Latin square low-density lattice codes (Latin square LDLCs) over unconstrained power additive white Gaussian noise channel. They benefit the properties of Latin square LDLCs to dramatically reduce the key size of the proposed scheme while having an acceptable level of security compared with previous similar schemes. To reduce the key size, they consider two approaches: (i) saving the generating sequence of parity-check matrix of used Latin square LDLC as the part of secret key set; (ii) employing the Hermite normal form of the generator matrix of used Latin square LDLC... 

In this study, the secret polar encoding and secret successive cancellation decoding algorithms are introduced; with these algorithms, secure and efficient communication can be enhanced between the honest parties. Also, the key size of the proposed polar code-based secure channel coding system is reduced significantly compared to the existing systems. To decrease the key size, the authors employ the three following methods: (i) a new approach is proposed to save some bit-channel indices instead of saving the generator matrix of the used polar code; (ii) the permutation and scrambling matrices are not used in this scheme; and (iii) by the help of the properties of polar codes, it does not... 

This letter presents an efficient polar code-based physical layer encryption (PLE) scheme with a short key length in comparison to the conventional symmetric key cryptosystems. By using the properties of polar codes, we consider several efficient techniques to reduce the key length and the computational overhead of the presented PLE scheme. Moreover, the results of the security analyses show that the proposed scheme has a high level of security against conventional attacks on the PLE schemes. In fact, reducing the key length and the computational overhead of the presented PLE scheme has no effect on its security level, which makes it suitable for secure mobile communication devices with...