Sharif Digital Repository

In this study, deactivation of Midrex reforming catalysts is evaluated kinetically by 3.5-year data of Mobarakeh Steel Company direct reduction site. The variation of Midrex catalyst’s structure is characterized by XRD and BET test. Two deactivation mechanism are characterized, methane cracking carbone deposition and sintering. The project results demonstrate that victorious mechanism is carbon deposition. The methane cracking carbone cause layer by layer deactivation of catalyst during 5.5 months. Although, XRD and BET showed pore volume and radius reduction and Ni crystal increasing, approximated constant activity of catalyst were approved by kinetic evaluation  

Outer membrane proteins play the role of molecular machines in the outer membrane of bacteria to regulate their basic functions. These macromolecules have nano-scale dimensions and they are involved in the classifications of nano-machines and nano-pores. Protein structure is constructed of chain of amino acids. Coarse grained elastic network model of the protein introduces a network of selected point masses, which is located on α-carbon of each amino acid, linked together with harmonic springs that represent the interactions between residues, both the chemical (protein backbone) and physical bonds. Using the harmonic network potential and theory of mechanical vibration, normal modes of... 

Polymers not just because of their increasing applications in industry but according to their fundamental role in biological mechanisms, has been a topic of interest among different scientific groups. Chemical structure, acroscopic properties and dynamical behavior of these macromolecules are studied in different ways. An important sub-group of polymers are those which according to their chemical properties, after dissolving, release some ions in water and become charged and called polyelectrolytes. A polyelectrolyte with vital importance in our life is DNA which encodes the genetic instructions used in the development and functioning of all known living organisms. One of the main goals in... 

Nowadays catalytic reforming of naphtha is one of the most important parts of the refining process. The catalyst of this process is mostly Pt-Re on the γ-alumina support. The major cause of deactivation is coke deposition and blockage of the pores as a result. Meanwhile, modeling of the process and the deactivation of catalyst would help refining industries to achieve higher yields. In this study industrial data of the catalytic reforming unit #2 in Isfahan Refinery Plant were used to model the process, optimized parameters have been calculated and the best contribution of the catalyst among the four reactors was presented. Then with using a deactivation function the whole coking... 

Polymer translocation through the nanopores is one of the fundamental macromolecular processes in life. Some examples are , mRNA translocation through nuclear pores, injection of DNA from a virus head into a host cell, protein translocation across biological membranes through membrane channels. Also some applications are suggested for the process, e.g. DNA sequencing by probing the signals during the translocation, drug delivery and/or gene therapy. During the translocation the polymer should pass entropic barrier of the pore and it can be facilitated by changing the chemical potential, application of eclectic field, flow field, or chemical concentrations. In electrically driven... 

Electrophoresis of colloidal and bio-particles, which is the motion of a charged particle under an electric field, is a powerful method for the characterization and separation of particles. Electrophoresis of particles could be in electrolyte and gel mediums. Additional drag force is exerted on the particle in a gel medium due to the 3D polymeric structure. Experimental research and molecular dynamics simulations have shown that the no-slip boundary condition is not valuable for many particles in micro and nano-devices. The Navier slip condition, which represents the amount of slip, must replace the no-boundary condition. Characterization of hydrophobicity for optimal design in microfluidic... 

The advent of nanopore-based sensors based on resitive pulse sensing gave rise to a remarkable breakthrough in the detection and characterization of nanoscale species. The sensors can detect the species’concentration, size, and charge using the resistive pulse characteristics. Some strong correlations have been reported between the resitive pulse characteristics and the particle’s geometrical and physical properties. These correlations are commonly used to obtain information about the particles in commercial devices and research setups. The correlations, however, do not consider the simultaneous effect of influential factors such as particle shape, charge, and off-axis translocation, which... 

Resistive pulse sensing (RPS) has proved to be a viable method for detection and characterization of micro and nano particles. This method works based on ionic current variation inside nanopores. Modern fabrication methods have introduced different nanopore geometries for resistive pulse sensors therefore studing the effects of geometry on sensing performance of nanaopores is important. Numerical simulation has been used to study a wide variation of nanopore’s geometry configurations and study the physics behind this phenomena. Based on the results, numerical simulation could be used as a fast and easy tool for size determination for nanopore. To compare the sensing performance of different...