Sharif Digital Repository

The objective of the present work is development of joint approximate diagonalization of eigenmatrices (JADE) as a member of independent component analysis (ICA) family, for the analysis of gas chromatography-mass spectrometry (GC–MS) and comprehensive two-dimensional gas chromatography-mass spectrometry (GC × GC–MS) data to address incomplete separation problem occurred during the analysis of complex sample matrices. In this regard, simulated GC–MS and GC × GC–MS data sets with different number of components, different degree of overlap and noise were evaluated. In the case of simultaneous analysis of multiple samples, column-wise augmentation for GC–MS and column-wise super-augmentation... 

This study investigated the effects of combined utilization of wollastonite particles and recycled waste ceramic aggregate (RWCA) on high strength concrete (HSC) properties. Two groups of mixtures were manufactured: 1) concrete mixtures in which cement was partially replaced with wollastonite at values ranging from 10% to 50%, and 2) mixtures in which wollastonite was used at the aforementioned dosages and 50% of natural coarse aggregate was replaced with RWCA. In addition, 10% of cement weight micro-silica was added to all mixtures. The concrete behavior in terms of strength, durability, resistance against acidic environment, and performance under elevated temperatures ranging from 20 °C to... 

The separation of xylene isomers is an important application in separation processes that is based on their adsorption properties on different adsorbents. In this work, the Price and Danner method was employed with a neural network to investigate the adsorption behavior of binary systems of p-xylene/m-xylene, p-diethyl benzene/m-xylene, and p-diethyl benzene/p-xylene and the ternary system of p-diethyl benzene/m-xylene/p-xylene at 130 and 175°C. The Redlich-Kister, Wilson, and NRTL models were used to determine the activity coefficients in the adsorbed phase. Comparison with experimental data from the literature indicated that the proposed thermodynamic model would best determine surface... 

The effects of H2O/SiO2, TMAOH/SiO2, Na/(Na+K), and SiO2/Al2O3 ratios in the parent gels on the crystallization of nanoparticles of T-type zeolites were studied. A Taguchi orthogonal experimental design with the above-mentioned parameters (each at three levels) was used to optimize the experiment parameters by the analysis of variances (ANOVA). Applying the Taguchi method significantly reduced the time and cost required for optimization. The synthesized products were characterized by X-ray diffraction and scanning electron microscopy. As a result of the Taguchi analysis, H2O/SiO2 and TMAOH/SiO2 were the most influencing parameters for the synthesis of zeolite T. © 2009 WILEY-VCH Verlag GmbH... 

The use of a draft tube fluidized bed bioreactor (DTFBB) has been successfully demonstrated for the bioleaching of a chalcopyrite concentrate (Mousavi, et. al., 2005). In the present paper this technique was used for the bioleaching of zinc from a sphalerite bearing low-grade ore. A strain of the thermophilic bacterium, Sulfobacillus, has been isolated from the Kooshk lead and zinc mine near the city of Yazd (Iran) and is tested at temperatures 47 °C-72 °C. This is compared to leaching with a strain of the mesophile Acidithiobacillus ferrooxidans, which has been adapted to the high levels of zinc and the presence of the low-grade ore, and which was tested at temperatures 18 °C-42 °C. The... 

An acid treatment of the cordierite monolith followed by coating of the CNT onto it by means of catalytic decomposition of methane was performed. The resulting material utilized as the support for the CoMo catalyst. The characterization outcomes showed that the CNTs were distributed uniformly on the surface of the monolith leading to a high BET surface area and relatively good adhered mesoporous layer of CNTs. Moreover, the catalytic activity of the resulting catalysts determined in an HDS reaction of naphtha. It was concluded that the activity of the CoMo catalyst over the CNT coated monolithic support (FACNT) was higher than that of the CoMo deposited onto the acid-treated monolith and... 

The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over... 

Centrifugal microfluidics or the Lab on a CD (LOCD) has developed vast applications in biomedical researches and analyses. Fluid mixing is an application of the LOCD. In this paper, multiple centrifugal micromixers were simulated. Various parameters were originally presumed to have an effect on mixing performance. These parameters include inlet angle, angular velocity, cross-sectional profile, perpendicular length ratio and the number of channels in series. They were each analyzed through simulations. It was gathered that the inlet angle does not significantly affect the mixing quality. Increasing angular velocity steadily increases mixing quality for all geometries. The vertical triangular... 

The Lab On a CD (LOCD), also known as Centrifugal Microfluidics, has evolved into a sophisticated platform for performing biomedical assays due to its marvelous miniaturization and accurate simulation of biological reactions. Among the numerous applications of the LOCD is fluid mixing. In this paper a centrifugal, serpentine micromixer is simulated and reformed toward better mixing performance. The micromixer was chosen to be curved as a curved design was found to be thrice as functional and compact as a rectilinear design, mixing-wise. The two angular velocity and opening radius parameters were originally hypothesized to affect mixing performance. Effect of angular velocity was studied over... 

Inertial particle focusing as a powerful passive method is widely used in diagnostic test devices. It is common to use a curved channel in this approach to achieve particle focusing through balancing of the secondary flow drag force and the inertial lift force. Here, we present a focusing device on a disk based on the interaction of secondary flow drag force, inertial lift force, and centrifugal forces to focus particles. By choosing a channel whose cross section has a low aspect ratio, the mixing effect of the secondary flow becomes negligible. To calculate inertial lift force, which is exerted on the particle from the fluid, the interaction between the fluid and particle is investigated... 

Petroleum monoaromatics including benzene, toluene, ethylbenzene, and xylenes (BTEX) are among the notorious volatile organic compounds that contaminate water and soil. In this study, a surfactant- modified natural zeolite and its relevant granulated nanozeolites were evaluated as potential adsorbents for removal of petroleum monoaromatics from aqueous solutions. All experiments performed in batch mode at constant temperature of 20°C and pH of 6.8 for 48 h. The results revealed that the amount of BTEX uptake on granulated zeolites nanoparticles were remarkably higher than the parent micron size natural zeolite (in the order of four times). The isotherms data were analyzed using five models... 

Microfluidic-based concentration gradient generators (CGGs) have a number of applications in chemical, biological and pharmaceutical studies. Thus, precise design of the microfluidic system is crucial to maintaining the desired concentration gradient in microchannels. One of the design considerations is the length of microchannels in the structure of a CGG. A CGG with a short length fails to provide the complete diffusive mixing, while the size of the microchip would unfavorably increase by incorporating a long CGG. Considering a CGG as a tree-like structure consisting of T-shaped micromixers, the mixing process of the species at a straight microchannel has been solved analytically. Herein,... 

Depending on the type of dopant metal, many kinds of zircon based pigments are produced and blue vanadium pigment is the most important one of them. In this study, blue zircon ceramic pigments were synthesized from intermediate product, resulting from decomposition of zircon sand with NaOH. In this regard, various amounts of sulfuric acid, water, NH4VO3 as colorant, NaF as mineralizer and extra quartz were added to the prepared Na 2ZrSiO5. Role of quartz was to omit the repercussions of presence of free zirconia in the composition. The main objective of this work is to assess various reactions at different temperatures during blue pigment synthesis. Phase analysis was done by X ray... 

Polyethylene/clay nanocomposites (PECNC) were synthesized via in situ Ziegler-Natta catalyst polymerization. Activated catalyst for polymerization of ethylene monomer has been prepared at first by supporting of the cocatalyst on the montmorillonite (MMT) smectite type clay and then active complex for polymerization formed by reaction of TiCl4 and aluminum oxide compound on the clay. Acid wash treatment has been used for increasing hydroxyl group and porosity of the clay and subsequently activity of the catalyst. The nano- structure of composites was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Obtained results show that silica layers of the mineral clay... 

In this paper, preparation of polyethylene/clay nanocomposites (PECNC) by in situ Ziegler-Natta catalyst polymerization was investigated. A Ziegler-Natta catalyst was first supported on montmorillonite (MMT) type clay and subsequently used for polymerizing ethylene. Clay and clay supported catalyst were characterized by Fourier transmission infrared and ICP method. X-ray diffraction (XRD) and transmission electron microscopy results show that silicate layers of the mineral clay in prepared nanocomposites were intercalated and exfoliated in the polymeric matrix. Differential scanning calorimetry results show that the prepared nanocomposites have higher crystallization temperature than pure... 

In this article, preparation of polypropylene/clay nanocomposites (PPCNC) via in situ polymerization is investigated. MgCl2/montmorillonite bisupported Ziegler-Natta catalyst was used to prepare PPCNC samples. Montmorillonite (MMT) was used as an inert support and reinforcement agent. The nanostructure of the composites was characterized by X-ray diffraction, scanning electron microscopy, and transmission electron microscopy techniques. Obtained results showed that silica layers of the MMT in these PPCNC were intercalated, partially exfoliated, and uniformly dispersed in the polypropylene matrix. Thermogravimetric analysis showed good thermal stability for the prepared PPCNC. Differential... 

In this paper, the effects of two methods of iridium impregnation into HZSM-5 on catalyst stability, selectivity for propylene and byproducts in the conversion of methanol to propylene (MTP) were investigated in a continuous flow isotherm fixed-bed reactor. XRD, BET surface area, NH 3-TPD and ICP-AES analytical techniques were applied to define the physical and chemical characteristics of zeolites. The reaction was conducted at 480°C and 1 bar with WHSV = 1 h -1, and with an equal weight percent of methanol and water in the feed. The results revealed that iridium impregnation into HZSM-5 powder led to enhanced propylene selectivity (8%) and catalyst stability while iridium impregnation into... 

Medium-pore (diameter - 6A) zeolites such as ZSM-5 and silicalite impregnated with Group VIII metals provide selective catalytic pathways for the conversion of synthesis gas to gasoline or olefins. Mössbauer and magnetic studies on these catalysts containing iron or iron plus cobalt are reported. The zeolites were impregnated with metal nitrate solutions, reduced, and carbided to yield showed Fe3+ type spectra. The ZSM-5 (14.7 % Fe) and Silicalite (13.6 % Fe) samples exposed to H2 (450 C) showed an approximate 85% reduction to the metallic state. The carbided ZSM-5 (14.7 % Fe) revealed a spectrum of Hagg carbide (Fe5C2), an active component of the catalyst. The used catalysts showed mixtures... 

A near fully dense mullite-TiB2-CNTs hybrid composite was prepared successfully trough spark plasma sintering. 1 wt%CNT and 10 wt%TiB2 were mixed with nano-sized mullite powders using a high energy mixer mill. Spark plasma sintering was carried out at 1350 °C under the primary and final pressure of 10 MPa and 30 MPa, respectively. XRD results showed mullite and TiB2 as dominant crystalline phases accompanied by tiny peaks of alumina. The microstructure of prepared composites demonstrated uniform distribution of TiB2 reinforcements in mullite matrix without any pores and porosities as a result of near fully densified spark plasma sintered composite. The fracture surface of composite revealed... 

The objective of this study was to evaluate the effects of P 2O5 particle size distribution on the crystalline phases and microstructure of lithium disilicate glass-ceramics derived from the TiO2-ZrO2-Li2O-CaO-Al2O 3-SiO2 system for dentistry applications. The samples were made via fusion and casting procedure. Crystallisation as well as the morphology and microstructure of the samples were investigated using X-ray diffraction, differential scanning calorimetric and scanning electron microscopy. The results showed that the crystallisation of the samples occurred in the range of 500-650°C. The main crystalline phase was lithium disilicate (Li2Si2O5) along with Lithium metasilicate (Li2SiO3),...