Sharif Digital Repository

In this work, the preparation of a new grafted nanosilica-based sorbent was extensively investigated. An inexpensive modifier, cis-9-octadecenoic acid (oleic acid) was selected to be grafted on the surface of the nanosilica particles as the support. The grafting process was accurately confirmed by Fourier transform infra-red spectrometry (FT-IR). Applicability of the prepared sorbent was thoroughly examined by needle trap extraction (NTE) method. The grafted sorbent was dispersed in the appropriate solvent and carefully packed inside a steel needle. Feasibility of the method was completely examined using polycyclic aromatic hydrocarbons (PAHs), as model compounds. For extraction of analytes... 

Let T be a partial Latin square and L a Latin square such that T ⊆ L.Then T is called a Latin trade, if there exists a partial Latin square T * such that T* ∩ T = ∅ and (LT) ∪ T* is a Latin square.We call T* a disjoint mate of T and the pair (T,T*) is called a Latin itrade.A Latin bitrade where empty rows and columns are ignored, is called a Κ-homogeneous Latin bitrade, if in each row and each column it contains exactly κ elements, and each element appears exactly k times.The number of filled cells in a Latin trade is referred to as its volume.Following the earlier work on κ-homogeneous Latin bitrades by Cavenagh, Donovan, and Drápal (2003 and 2004) Bean, Bidkhori, Khosravi, and... 

A method based on immersed solid-phase microextraction (SPME) and gas chromatography mass spectrometry detection (GC-MS) for the determination of organophosphorous pesticides (OPPs) in aqueous samples was developed. A sol-gel based coating fiber was prepared using 3-(trimethoxysilylpropyl) amine as precursor. The synthesized fiber was prepared in a way to impart polar moiety into the coating network and would be more suitable for extracting polar and semi-polar organic pollutants. Important parameters influencing the extraction process were optimized and an extraction time of 40 min at 30 °C gave maximum peak area, when NaCl (20% w/v) was added to the aqueous sample. The linearity for... 

A headspace solid-phase dynamic extraction (HS-SPDE) technique was developed by the use of polypyrrole (PPy) sorbent, electropolymerized inside the surface of a needle, as a possible alternative to solid-phase microextraction (SPME). Thermal desorption was subsequently, employed to transfer the extracted analytes into the injection port of a gas chromatography-mass spectrometry (GC-MS). The PPy sorbent including polypyrrole-dodecyl sulfate (PPy-DS) was deposited on the interior surface of a stainless steel needle from the corresponding aqueous electrolyte by applying a constant deposition potential. The homogeneity and the porous surface structure of the coating were examined using the... 

In this article, the size-dependent behavior of micro-beams with the thermoelastic damping (TED) phenomenon is studied. The coupled thermoelasticity equations are derived on the basis of the modified couple stress theory (MCST) and dual-phase-lag (DPL) heat conduction model. By solving these coupled equations simultaneously, a closed-form expression for the TED parameter in micro-beams is presented which considers the small-scale effects incorporation. Then, the effect of various parameters on TED in micro-beams, such as micro-beam height, the type of material, boundary conditions, and aspect ratio is investigated. The results show that the influence of utilizing non-classical continuum and... 

In this research, the small-scale effects in the torsional vibration of the micro-rotors with eccentric micro-disks are investigated based on the modified couple stress theory. The torsional deformation of the micro-shaft described by function φ(x,t) is considered to be independent of the flexural deformation described by functions v(x,t) and w(x,t). Using Hamilton's principle, the system of coupled nonlinear governing partial differential equations of motion and the associated boundary conditions are derived. The system of equations includes one corresponding to the torsional deformation and two others corresponding to the flexural deformation. By employing the Galerkin method, the system... 

A fiber coating from polyaniline (PANI) was electrochemically prepared and employed for solid phase microextraction (SPME) of some polycyclic aromatic hydrocarbons (PAHs) from water samples. The PANI film was directly electrodeposited on the platinum wire surface in sulfuric acid solution using cyclic voltammetry (CV) technique. The applicability of this coating was assessed employing a laboratory-made SPME device and gas chromatography with mass spectrometry (GC-MS) for the extraction of some PAHs from the headspace of aqueous samples. Application of wider potential range in CV led to a PANI with more stability against the temperature. The homogeneity and the porous surface structure of the... 

A novel amino-functionalized polymer was synthesized using 3-(trimethoxysilyl) propyl amine (TMSPA) as precursor and hydroxy-terminated polydimethylsiloxane (OH-PDMS) by sol-gel technology and coated on fused-silica fiber. The synthesis was designed in a way to impart polar moiety into the coating network. The scanning electron microscopy (SEM) images of this new coating showed the homogeneity and the porous surface structure of the film. The efficiency of new coating was investigated for headspace solid-phase microextraction (SPME) of some environmentally important chlorophenols from aqueous samples followed by gas chromatography-mass spectrometry (GC-MS) analysis. Effect of different... 

An aniline-based polymer was electrochemically prepared and applied as a new fiber coating for solid phase microextraction (SPME) of some priority phenols from water samples. The polyaniline (PANI) film was directly electrodeposited on the platinum wire surface in sulfuric acid solution using cyclic voltammetry (CV) technique. The efficiency of new coating was investigated using a laboratory-made SPME device and gas chromatography with flame ionization detection for the extraction of some phenols from the headspace of aqueous samples. The scanning electron microscopy (SEM) images showed the homogeneity and the porous surface structure of the film. The results obtained proved the ability of... 

The aim of this study is to introduce an extractive phase based on gradient concept by continuous changing in chemical functional groups for non–targeted analysis. For this purpose, three different two–component coatings containing (3–aminopropyl)trimethoxysilane (APTES) as polar and either phenyltriethoxysilane (PTES), octyl–trimethoxysilane (OTMS) or methyltrimethoxysilane (MTMS) as nonpolar precursors were formed on the modified stainless steel wires using controlled rate infusion (CRI) method. The presence of polar and/or non–polar functional groups on the surface of substrate was evaluated by Fourier–transform infrared spectroscopy (FTIR) together with contact angles determined... 

Liquid-liquid-liquid microextraction (LLLME) in combination with HPLC and UV detection has been used as a sensitive method for the determination of ephedrine in urine samples. Extraction process was performed in a homemade total glass vial without using a Teflon ring, usually employed. Ephedrine was first extracted from 3.5 mL of urine sample (pH 12) into a microfilm of toluene/benzene (50:50). The analyte was subsequently back extracted into an acidic microdrop solution (pH 2) suspended in the organic phase. The extract was then injected into the HPLC system directly. An enrichment factor of 137 along with a good sample clean-up was obtained under the optimized conditions. The calibration... 

Sport video shot classification is a basic step in the sport video processing. For many purposes such as event detection and summarization, shot classification is needed for content filtering. In this paper, we present a new method for soccer video shot classification. At first, in-field and out-of-field frames are separated. In in-field frames three features based on number of connected components and shirt color percent in vertical and horizontal strips are extracted. The features are all new and showed excellent discrimination in the feature space. These features are given to SVM for classifying long, medium and close-up shots. One of the advantages of our method is that, close-ups can be... 

A μ-way Latin trade of volume s is a collection of μ partial Latin squares T1, T2,⋯, Tμ, containing exactly the same s filled cells, such that, if cell (i,j) is filled, it contains a different entry in each of the μ partial Latin squares, and such that row i in each of the μ partial Latin squares contains, set-wise, the same symbols, and column j likewise. It is called a μ-wayk-homogeneous Latin trade if, in each row and each column, Tr, for 1≤r≤μ, contains exactly k elements, and each element appears in Tr exactly k times. It is also denoted as a (μ,k,m) Latin trade, where m is the size of the partial Latin squares. We introduce some general constructions for μ-way k-homogeneous Latin... 

A micro-SPE technique was developed by fabricating a rather small package including a polypropylene membrane shield containing the appropriate sorbent. The package was used for the extraction of some triazine herbicides from aqueous samples. Solvent desorption was subsequently performed in a microvial and an aliquot of extractant was injected into GC-MS. Various sorbents including aniline-ortho-phenylene diamine copolymer, newly synthesized, polypyrrole, multiwall carbon nanotube, C18 and charcoal were examined as extracting media. Among them, conductive polymers exhibited better performance. Influential parameters including extraction and desorption time, desorption solvent and the ionic... 

A feasible and low cost approach to implement a nonplanar dual-polarized log-periodic dipole array antenna using printed circuit board (PCB) technology is proposed. The proposed antenna utilizes a very short transition from a coaxial cable to a balanced twin-lead transmission line to realize an ultrawide bandwidth balun, and has two distinct scaling factor values for high and low frequency elements. A prototype of the antenna operating over the frequency range of 1-13 GHz was designed, fabricated, and tested. An average gain of 7 dBi is obtained. Measured VSWR, cross-polarization and front-to-back ratio are better than 2.6, -16 dB, and 22 dB, respectively  

A novel high-throughput device based on 96-micro-solid phase extraction (96-μ-SPE) system was constructed for multiresidue determination of nine pesticides in aquatic samples. The extraction procedure was performed on a commercially available 96-well plate system. The extraction module consisted of 96 pieces of 1cm×3cm of cylindrically shaped stainless steel meshes. The prepared meshes were fixed in a home-made polytetrafluoroethylene-based constructed ninety-six holes block for possible simultaneous immersion of meshes into the center of individual wells. Dodecyl methacrylate and ethylene glycol dimethacrylate was copolymerized as a monolithic polymer and placed in the cylindrically shaped... 

Despite the great promise of hybrid solar-wind-biomass energy systems to power future sustainable cities, complexities associated with their optimal planning and design limit their wide-scale implementation. This study provides a novel systematic framework to identify optimal hybrid renewable solutions for urban areas at neighborhood scales. In particular, we examine the role of economies of scale in the techno-economic feasibility and environmental performance of hybrid renewable systems. For demonstration, we assess the impact of the economics of scale (at the neighborhood scales of 1/500, 1/250, and 1/100 of the city's electrical load) on the life-cycle costs of optimal hybrid renewable... 

An improved method of friction stir processing (FSP) was introduced for the processing of AZ91 magnesium alloy specimens. This novel process was called “friction stir vibration processing (FSVP)”. FSP and FSVP were utilized to develop surface composites on the studied alloy while SiC nanoparticles were applied as second-phase particles. The effect of reinforcing SiC particles with different sizes (30 and 300 nm) on different characteristics of the composite surface was studied. The results indicated that the microstructure was refined and mechanical properties such as hardness, ductility, and strength were enhanced as FSVP was applied. Furthermore, it was concluded that the effect of... 

Kernel learning is one of the most important and recent approaches to constrained clustering. Until now many kernel learning methods have been introduced for clustering when side information in the form of pairwise constraints is available. However, almost all of the existing methods either learn a whole kernel matrix or learn a limited number of parameters. Although the non-parametric methods that learn whole kernel matrix can provide capability of finding clusters of arbitrary structures, they are very computationally expensive and these methods are feasible only on small data sets. In this paper, we propose a kernel learning method that shows flexibility in the number of variables between... 

The great surge in the research of community discovery in complex network is going on due to its challenging aspects. Dynamicity and overlapping nature are among the common characteristics of these networks which are the main focus of this paper. In this research, we attempt to approximate the granular human-inspired viewpoints of the networks. This is especially helpful when making decisions with partial knowledge. In line with the principle of granular computing, in which precision is avoided, we define the micro- and macrogranules in two levels of nodes and communities, respectively. The proposed algorithm takes microgranules as input and outputs meaningful communities in rough...