Sharif Digital Repository

Security techniques have been designed to obtain certain objectives. One of the most important objectives all security mechanisms try to achieve is the availability, which insures that network services are available to various entities in the network when required. But there has not been any certain parameter to measure this objective in network. In this paper we consider availability as a security parameter in ad-hoc networks. However this parameter can be used in other networks as well. We also present the connectivity coefficient of nodes in a network which shows how important is a node in a network and how much damage is caused if a certain node is compromised  

Performance of routing is severely degraded when misbehaving nodes drop packets instead of properly forwarding them. In this paper, we propose a Game-Theoretic Adaptive Multipath Routing (GTAMR) protocol to detect and punish selfish or malicious nodes which try to drop information packets in routing phase and defend against collaborative attacks in which nodes try to disrupt communication or save their power. Our proposed algorithm outranks previous schemes because it is resilient against attacks in which more than one node coordinate their misbehavior and can be used in networks which wireless nodes use directional antennas. We then propose a game theoretic strategy, ERTFT, for nodes to... 

The impact of modified magnetite nanoparticles (MMNPs)on hydrodynamics and mass transfer in liquid–liquid extraction process was assessed using a ternary chemical system of toluene-acetic acid–water. The organic phase which contained toluene and acetic acid was dispersed through water, and the mass transfer of acetic acid between two phases was investigated. The hydrophobic modified magnetite nanoparticles (MMNPs)prepared through an optimized in-situ method were added to the dispersed phase at different concentrations (0.001−0.005 wt%). Two separate conditions were provided in the experiments, i.e. stagnant and stirred continuous phase. The latter case was provided by a rotor at two... 

The Burr XII distribution can closely approximate many other well-known probability density functions such as the normal, gamma, lognormal, exponential distributions as well as Pearson type I, II, V, VII, IX, X, XII families of distributions. Considering a wide range of shape and scale parameters of the Burr XII distribution, it can have an important role in reliability modeling, risk analysis and process capability estimation. However, estimating parameters of the Burr XII distribution can be a complicated task and the use of conventional methods such as maximum likelihood estimation (MLE) and moment method (MM) is not straightforward. Some tables to estimate Burr XII parameters have been... 

A convenient and efficient procedure was developed for preparing α,α′-icyanostilbenes through the oxidative coupling reaction of benzyl cyanide derivatives using N-benzyl DABCO tribromide as the oxidative bromination reagent in the presence of K2CO3 as a base. Copyright © Taylor & Francis Group, LLC  

4-Aminoperoxybenzoic acid supported on silica gel in presence of oxygen or air was found to be a convenient and selective oxidant for the oxidation of benzylic methylene compounds to the corresponding ketones  

Kieselguhr supported copper chloride catalyses the oxidation of thiols to disulfides in the presence of oxygen or air  

This paper reports on the recovery of zinc, cobalt and manganese by two-step leaching of zinc-plants purification residue with sulfuric acid. The residue, hot filter press cake (HFC), contains 14 % ZnO, 4.8 % Co 3O4 and 22.9 % MnO. Effects of different parameters are determined and used to optimize the process. With acid to hot filter press cake (HFC) stoichiometry of 0.85, acid concentration of 30 g/L and temperature of 25°C, it took two minutes to separate zinc from zinc plant residue. Hydrogen peroxide (H2O2) was used as an oxidation agent. The most suitable acid concentration for leaching of both cobalt and manganese was 50 g/L. Recovery of cobalt and manganese increased with peroxide... 

The non-symmetrical tetradentate Schiff-base H2L have been obtained using the half-unit N-(1-hydroxy-2-acetonaphthone)-1-amino-2- phenyleneimine (HL1) with 2-hydroxyl-1-naphthaldehyde. ML complexes(M = Ni(1), Cu(2), Co(3) and Zn(4)) were prepared and characterized by atomic absorption, IR, UV, 1H NMR spectroscopy, and a single crystal X-ray structure. Crystal data for (1) are triclinic space group P-1, a = 7.9784 (3) A, b = 10.2417 (4) A, c = 13.4090 (5) A, α = 103.8480 (10)°, β = 97.0540 (10)°, γ = 92.2400 (10)° and z = 2. Crystal data for (2): Triclinic space group P-1, a = 7.9991 (6) A, b = 10.0520 (7) A, c = 13.6974 (10) A, α = 103.6500 (10)°, β = 95.9650 (10)°, γ = 90.3160 (10)° and z =... 

The preparation and electrochemical performance of the carbon nanotube-paste electrode modified with salophen complexes of cobalt(III) perchlorate, with various substituents on the salophen ligand, as well as their electrocatalytic activity toward the oxidation of N-acetylcysteine (NAC) is investigated. Several Schiff base complexes containing various nucleophilic and electrophilic functional groups were prepared, and their electrochemical characteristics for the electro-oxidation of NAC were evaluated using cyclic and differential pulse voltammetry (CV and DPV). The results revealed, the modified electrodes show an efficient and selective electrocatalytic activity toward the anodic... 

We analyze the set ANQ of mixed unitary channels represented in the Weyl basis and accessible by a Lindblad semigroup acting on an N-level quantum system. General necessary and sufficient conditions for a mixed Weyl quantum channel of an arbitrary dimension to be accessible by a semigroup are established. The set ANQ is shown to be log-convex and star-shaped with respect to the completely depolarizing channel. A decoherence supermap acting in the space of Lindblad operators transforms them into the space of Kolmogorov generators of classical semigroups. We show that for mixed Weyl channels, the super-decoherence commutes with the dynamics so that decohering a quantum accessible channel, we... 

Three ternary copper(II) complexes [Cu(5-bromo-salTyr)(bipy)]·1/ 2CH3OH (1), [Cu(5-bromo-salLue)(bipy)]·CH3OH (2) and [Cu(5-bromo-salTrp)(bipy)]·3CH3OH (3) (where 5-bromo-salTyr, 5-bromo-salLue and 5-bromo-salTrp are tridentate Schiff base ligands derived from the condensation of 5-bromosalicylaldehyde with tyrosine, leucine and tryptophan, respectively, and bipy is 2,2′-bipyridine) have been prepared and characterized by elemental analysis, electronic, IR spectroscopies, magnetic measurement and cyclic voltammetry. The complexes, 1 and 3 have been also structurally characterized by X-ray diffraction technique. Crystal structures of 1 and 3 complexes displayed a distorted square-pyramidal... 

The preparation of two new bis(N-heterocyclic carbene) platinum(ii) complexes, in which NHC rings are joined by a CH2 linker group, is described. While, the chelate complex [PtMe2(bis-NHC1)], 1, was formed with large tert-butyl wingtips, the iso-propyl N-substituent analogue favors formation of the cluster complex [Pt2Me4(μ- SMe2)(μ-bis-NHC2)]2(μ-Ag2Br2), 2, in which two binuclear platinum(ii) complexes are linked together by an Ag2Br2 unit. The chelating platinum complex 1 undergoes aerial CO2 fixation and forms platinum(ii) carbonate complex [Pt(CO3)(bis-NHC1)], 3  

Conditions for an efficient ligand-free Heck C-C coupling reaction of aryl iodides and bromides with terminal olefins under aerobic conditions have been developed. Critical to the success of this new protocol is the use of palladium acetate as an extremely active catalyst for the Heck reaction in water and aqueous media. Both the base and the solvent were found to have a fundamental influence on the efficiency of the reaction, with K2CO3 and a mixture of (2:1) H2O/DMSO being the optimal base and solvent, respectively  

Alluring optical and electronic properties have made organometallic halide perovskites attractive candidates for optoelectronics. Among all perovskite materials, inorganic CsPbX3 (X is halide) in black cubic phase has triggered enormous attention recently owing to its comparable photovoltaic performance and high stability as compared to organic and hybrid perovskites. However, cubic phase stabilization at room temperature for CsPbI3 still survives as a challenge. Herein we report all inorganic three-dimensional vertical CsPbI3 perovskite nanowires (NWs) synthesized inside anodic alumina membrane (AAM) by chemical vapor deposition (CVD) method. It was discovered that the as-grown NWs have... 

N-Benzyl-DABCO-ammonium tribromide was found to be an efficient and recyclable reagent for the deprotection of dithioacetals in dichloromethane/ methanol at room temperature. The reaction can be performed cleanly, in short time, and in high yield. Copyright © Taylor & Francis Group, LLC  

The asymmetric synthesis of ,-disubstituted -bisalkoxycarbonyl sulfonates is reported. The synthesis is based on the Michael addition of a lithiated enantiopure sulfonate bearing a cheap chiral sugar auxiliary to Knoevenagel acceptors. The reaction proceeds with high asymmetric inductions (ds=69-96%) and good yields (62-79%). The absolute configuration was determined by X-ray crystal-structure analysis  

Three-dimensional macroporous fluorine-doped tin oxide (p-FTO) films were successfully deposited using commercial ink of FTO powder and SnCl2 salt via Dr. Blade method. Various features of p-FTO thin films were studied as a function of the ink composition and sintering temperature. The morphological studies corroborated formation of porous, uniform, and crack-free FTO films after annealing at 300 °C for 10 min in air. X-ray diffraction pattern demonstrated development of highly crystalline FTO films. The lowest sheet resistance of 47 Ω/□ was obtained for the p-FTO film with a thickness of 21 μm. The capacitance of thin p-FTO films was investigated using a three-electrode system and the... 

Lake Urmia in northwestern Iran is the largest lake in Iran and the second largest saltwater lake in the world. The water level in Lake Urmia has decreased dramatically in recent years, due to drought, climate change, and the overuse of water resources for irrigation. This shrinking of the lake may affect local climate conditions, assuming that the lake itself affects the local climate. In this study, we quantified the lake's impact on the local climate by analyzing hourly time series of data on climate variables (temperature, vapor pressure, relative humidity, evaporation, and dewpoint temperature for all seasons, and local lake/land breezes in summer) for the period 1961-2016. For this, we...