Sharif Digital Repository

Polyaniline nanofiltration membranes were synthesized to examine a potential candidate for application of solvent recovery from lube oil. An integrally skinned polyaniline membrane was cast on a woven polyester fabric and then was chemically crosslinked with glutaraldehyde in order to further increase the membranes resistant in a methyl ethyl ketone and toluene mixture. Subsequently, membrane performance was tested under different operational conditions. The operation pressure was fixed at 35 bar and was held constant for all of the tests. The membrane demonstrated a permeate flux of 10 l/(m 2  h) and oil rejection of 69%. Abbreviations: PANi: Polyaniline; PI: polyimide; MEK: methyl ethyl... 

Gold-catalyzed cyclization of 1,5-diynes with ketones as reagents and solvent provides diversely substituted vinyl ethers under mild conditions. The regioselectivity of such gold-catalyzed cyclizations is usually controlled by the scaffold of the diyne. Herein, we report the first solvent-controlled switching of regioselectivity from a 6-endo-dig- to 5-endo-dig-cyclization in these transformations, providing fulvene derivatives. With respect to the functional-group tolerance, aryl fluorides, chlorides, bromides, and ethers are tolerated. Furthermore, the mechanism and selectivity are put to scrutiny by experimental studies and a thermodynamic analysis of the product. Additionally,... 

Density functional theory method and B3LYP/6-311++G(d,p) level of theory were used to determine the acidity of α-carbon in the hydroxyl derivatives of beta diketones in the gas phase. An investigation of acidity strength in the gas phase indicates that α-carbon of hydroxyl derivatives of beta diketones become stronger acids than the α-carbon of beta diketone itself as their conjugate bases gain more stability via both enolate and hydrogen bond formation. Natural bond orbital and quantum theory of atoms in molecules analyses also confirm the role of hydrogen bond interactions on increasing the acidity of α-carbon of hydroxyl derivatives of beta diketones. © 2020 John Wiley & Sons, Ltd  

In the last three decades, nanoclay fillers have been increasingly used to improve the mechanical, thermal, barrier and biological properties of the polymers. Nevertheless, incorporation of clays into the hydrophobic polymer matrices leads to the formation of the microcomposites with the minimal improvement in properties. To overcome the intrinsic incompatibility between the clays and the hydrophobic polymers, clay particles are organophilized using organic modifiers. The organic modifier should be thermodynamically miscible with the polymer. In the case of the composites prepared at high temperatures, the organic modifier should also have a high thermal stability to withstand the processing... 

Recently, routing with disjoint paths has received much attention to provide more performance and fault tolerance. On the other hand, WK-recursive mesh network has been studied extensively due to its favorable properties such as high degree of stability and resilience. The connectivity of a network is an important measure of fault tolerance, while the diameter represents the worst-case transmission delay between two arbitrary nodes. In this paper, we propose one-to-one and one-to-many disjoint routings mechanisms for WK-recursive mesh networks to further exhibit the performance and fault tolerance of such networks. © 2008 IEEE  

In this paper, advantages of energy-efficient motors over standard-motors in terms of electrical energy saving and demand reduction in a tire-rubber factory are thoroughly evaluated. Energy-efficient motors reduce losses because of their better design, materials, and manufacturing. These motors are 2 to 8% more efficient than standard ones. Lengthening the core and using lower-electrical-loss steel, thinner stator laminations, and more copper in the windings reduce electrical losses. Because a motor consumes energy worth 4 to 10 times its own cost each year, energy-efficient motors often make economic sense in a wide variety of applications. At the end of this study, the amount of energy... 

After expanding the use of computer and its affect on different aspect of life, the copyright issue has gained many attractions. For this purpose watermarking methods are proposed. In these methods a code is embedded into digital material that can be used to approve ownership, it can be visible or invisible to the user. On the other hand with the rapid growth of mobile phones, mobile telecommunication companies starting to add additional features to their mobile phones such as MMS (Multimedia Messaging Service) in order to attract more customers. MMS is a technology that allows mobile phones sending messages that includes multimedia objects esp. images. For copyright protection of images... 

Gold nanoparticles are potentially very attractive components for therapeutic delivery since they can be synthesized with any diameter from 1 to 200 nm to carry a payload of therapeutic molecules into a cell without triggering an immune response. Gold nanoparticles must undergo surface transformations before coupling to therapeutic molecules to become eligible for this purpose. It is now more understood that amine groups can bind to gold nanoparticles strongly, which has enabled surface modification of gold nanoparticles with amino acid lysine through its amine group. These lysine capped gold nanoparticles can further be coupled to therapeutic molecules for delivery purposes. In this study... 

The second-order rate constants for cycloaddition reaction of cyclopentadiene with naphthoquinone were determined spectrophotometrically in various compositions of 1-(1-butyl)-3-methylimidazolium terafluoroborate ([bmim]BF4) with water and methanol at 25°C. Rate constants of the reaction in pure solvents are in the order of water > [bmim]BF 4 > methanol. Rate constants of the reaction decrease sharply with mole fraction of the ionic liquid in aqueous solutions and increase slightly to a maximum in alcoholic mixtures. Multi-parameter correlation of logk 2 versus solute-solvent interaction parameters demonstrated that solvophobicity parameter (Sp), hydrogen-bond donor acidity (α) and... 

People usually use trust and reputation to cope with uncertainty which exists in the nature and routines. The existing approaches for inferring trust rely on homogeneous relations. In other words, trust is just inferred by a homogeneous relation. In this paper, we present a new model for inferring trust using heterogeneous social networks; we use relation extraction to make a trust relation from the other relation such as friendship and the college relation and then introduced an algorithm to infer trust using extracted relation. In order to get higher performance, we extend relation extraction problem by proposing a genetic algorithm. This algorithm is more scalable, interpretable and... 

Bistatic passive radars have many advantages over the monostatic ones because they are undetectable and silent. In passive coherent location, the original source of energy is derived from a waveform of opportunity in the environment and the re-radiated energy from the target is processed to decide about the existence of the target. More over bistatic radars receive forward scatters from target in place of the backscatters in monostatics systems. As a result of the larger forward scattered RCS, the stealth targets can be detected easier. Passive radar does not need any frequency allocation so are very attractive for surveillance. Multipath effects and direct path interference are two problems... 

We study the effect of quantum motion in a Mach-Zehnder interferometer where ultracold, two-level atoms cross a π2-π-π2 configuration of separated, laser illuminated regions. Explicit and exact expressions are obtained for transmission amplitudes of monochromatic, incident atomic waves using recurrence relations which take into account all possible paths: the direct ones usually considered in the simple semiclassical treatment, but including quantum motion corrections, and the paths in which the atoms are repeatedly reflected at the fields. © 2008 The American Physical Society  

With the increasing number and complexity of network attacks, the demand for automatic vulnerability analysis tools has increased. The prerequisite of making these tools is to have a formal and precise model of network configurations and vulnerabilities. Utilizing this model, network administrators can analyze the effects of vulnerabilities on the network and complex attack scenarios can be detected before happening. In this paper, we present a general logic-based framework for modeling network configurations and topologies. Then, a number of important and wide-spread network vulnerabilities are modeled as general inference rules based on the framework definitions. We implemented the... 

A convenient one-pot multi-component reaction of aromatic aldehydes, enolizable ketones or β-keto esters and acetonitrile in the presence of acetyl chloride and 10 mol% ZnO nanoparticles for the synthesis of β-acetamido ketones/esters at room temperature is described. © 2007 Elsevier B.V. All rights reserved  

4-Aminoperoxybenzoic acid supported on silica gel was found to be a versatile and efficient oxidant for the oxidation of ketones to esters. Copyright © Taylor & Francis Group, LLC  

Under solvent free conditions between 40-50 °C, BF3.SiO 2, a mild solid acid catalyst, is applied to regio-chemo and stereoselective Claisen-Schmidt condensation. The procedure is very simple and the products are isolated with an easy workup in good to excellent yields  

An indirect colorimetric method is presented for detection of trace amounts of hydroquinone (1), catechol (2) and pyrogallol (3). The reduction of AuCl4- to Gold nanoparticles (Au-NPs) by these phenolic compounds in the presence of cetyltrimethylammonium chloride (CTAC) produced very intense surface plasmon resonance peak of Au-NPs. The plasmon absorbance of Au-NPs allows the quantitative colorimetric detection of the phenolic compounds. The calibration curves derived from the changes in absorbance at λ = 568 nm were linear with concentration of hydroquinone, catechol and pyrogallol in the range of 7.0 × 10-7 to 1.0 × 10-4M, 6.0 × 10-6 to 2.0 × 10-4 M and 6.0 × 10-7 to 1.0 × 10-4 M,... 

In this paper, we propose a new concept of relaying named parallel relaying to obtain a new achievable rate for relay networks. The proposed encoding scheme is based on partial decoding, where the relay decodes only part of the transmitted message. The superiority of our proposed method to the previous ones is that, it can be applied to the relay networks with general structure, not necessarily with feed-forward structure. The proposed achievable rate is also used to establish the capacity of a class of semi-deterministic relay network which is a generalization of Aref network. © 2008 IEEE  

Purpose - The purpose of this paper is to present research into reducing the aircraft design cycle period, by reducing the necessary number of design cycle iterations. The design cycle period is one of the main characteristics of the design process and design cycle iterations play a major role in the design cycle period. Design/methodology/approach - Toachieve the above-mentioned goal, the paper presents a mathematical model of iterations for the aircraft design process. This model describes the design coupled tasks as a discrete-linear time invariant dynamic system. This model also helps identify tasks which are the most important for generating iterations. This new method basically helps... 

A new high-performance architecture for decoding the irregular Low-Density Parity-Check (LDPC) codes with respect to the iterative message-passing decoding algorithm is explored. The proposed method is based on reducing the logic delays in the iterative processing of the bit nodes and check nodes leading to the increment of maximum possible frequency. The simulations show the efficiency of the proposed method in low/high-complexity graph matrices, though it is more effective in high-complexity ones. About 28% reduction of the combinational delay in the bit/check processors is explored without much impacting the area consumption. ©2007 IEEE