Sharif Digital Repository

Submicron sized polyacrylamide particles were prepared via modified precipitation polymerization method. Experimental design based on Taguchi approach was employed to study the influence of the polymerization composition including monomer (acrylamide), crosslinker (methylenebisacrylamide), initiator (azobisisobutyronitrile), and modifier (polyvinylpyrrolidone, K-30), on the size and morphology of the particles. Varying the polymerization composition, submicron-particles with sizes ranging between 100 and 600 nm were achieved. In all the cases, polydispersity index (PDI) of the particle size was found to be almost 1 indicating uniformity of the particle size. The concentration of crosslinker... 

Objective(s): Seizure detection during online recording of electrophysiological parameters is very important in epileptic patients. In the present study, online analysis of field potential recordings was used for detecting spontaneous seizures in epileptic animals. Materials and Methods: Epilepsy was induced in rats by pilocarpine injection. During the chronic period of the pilocarpine model, local field potential (LFP) recording was run for at least 24 hr. At the same time, video monitoring of the animals was done to determine the real time of seizure occurrence. Both power and sample entropy of LFP were used for online analysis. Results: Obtained results showed that changes in LFP power... 

Effect of organoclay (OC) on the performance of styrene-butadiene rubber (SBR)/phenolic resin (PH) blend prepared by two-roll mill was investigated. The influence of OC content ranging between 2.5 and 30 phr on the performance of SBR/PH was investigated using X-ray diffraction (XRD), scanning electron microscopy (SEM), interfacial energy analysis, tensile, dynamic mechanical, swelling, cure rheometry and thermogravimetric analysis (TGA). It was found that the OC is mainly localized in the SBR phase of SBR/PH blend through the kinetically favored mechanism relevant to rubber chains. The results also demonstrated the positive role of PH on the dispersion of OC. Both PH and OC showed... 

The present study deals with the structure-property relationship of organoclay (OC) filled nanocomposites based on rubber blend comprising of nitrile-butadiene rubber (NBR) and phenolic resin (PH). To obtain a better insight into the characteristics of the NBR/PH/OC hybrid system, a simple model system consisting of NBR/OC nanocomposites is also taken into consideration. A series of NBR/OC and NBR/PH/OC nanocomposites containing a wide range of OC concentrations (2.5-30 phr) are prepared by using traditional open two-roll mill. Structural analysis performed by X-ray diffraction (XRD), scanning electron microscope (SEM), and transmission electron microscope (TEM) exhibits mixed exfoliated and... 

Various compositions of maleated ethylene-propylene-rubber (EPR-g-MA) toughened polyamide 6 without and with short glass fiber, i.e. 5-20 wt.% rubber and 5-20 wt.% fiber, are prepared using an industrial twin-screw extruder at different levels of feed rate (100-250 kg/h), screw speed (200-450 rpm) and barrel temperature (230-260 °C). Trial runs designed based on the Taguchi's orthogonal arrays are subjected to tensile, impact, scanning electron microscopy (SEM) and optical microscopy tests; and the results are used to perform the analysis of variance (ANOVA). It is shown that the rubber particle size decreases significantly by increasing the rubber content for the unreinforced blend. The... 

Recently much attention has been paid to the use of low salinity water (LSW) as an enhanced oil recovery fluid. The change observed in recovery factor during LSW flooding is induced from changes in relative permeability and capillary pressure when different levels of salinity are used. However, a few researchers tried to evaluate how macroscopic flow functions depend on the salinity of the injected water. To this end, a series of oil displacement by water was performed on a sandstone rock aged with crude oil in the presence of connate water. The capillary pressure and relative permeability curves are evaluated from inverse modeling of the obtained pressure drop and oil production data. Then,... 

One of the basic challenges during drilling horizontal wellbores is the damage induced by invasion of mud filtrate into the formation. Addition of nanoparticles to drilling fluids has been recognized as a measure of control and reduction of filtrate invasion, which is the primary mechanism of the aforementioned formation damage. Despite notable advances in composing Nano-enhanced drilling fluids, the role of nanoparticle hydrophobicity on performance of the fluids has not been well studied. This study is based on a combined experimental-numerical methodology. In the experimental section, a procedure to find the optimum composition of Nano-enhanced water-based samples, containing... 

Cerium nitrate loaded polyaniline (PANI) nanofibers were synthesized in this work via a chemical route. PANI nanofibers act as a host structure for the corrosion inhibitor, forming a Ce(III)-PANI complex. This complex is pH sensitive, and a change of pH can cause breaking of the complex and releasing of Ce(III). The Ce(III) loaded PANI nanofibers were embedded into epoxy ester coating and the self-healing corrosion protection ability was investigated by Scanning Vibrating Electrode Technique (SVET) and Electrochemical Impedance Spectroscopy (EIS). The results showed that by embedding of Ce(III) loaded PANI nanofibers into the coatings a superior corrosion protection and self-healing... 

Nanostructured hollow polyaniline (PANI) capsules are good candidates for encapsulation of corrosion inhibitors and pH-responsive release when incorporated into organic coatings. In previous studies, the corrosion protection performance of PANI capsules, containing organic inhibitor 2-Mercaptobenzothiazole (MBT), was demonstrated. The present work studies the influence of capsule concentrations (i.e., 0.3, 1, and 2 wt%) on the corrosion protection properties of the coating system. Anti-corrosion properties of different coatings were compared by means of Electrochemical Impedance Spectroscopy (EIS) and Scanning Vibrating Electrode Technique (SVET). MBT loaded PANI capsules in epoxy ester... 

Removing of arsenic and antimony from electrolyte of copper electrorefining plant by cooling treatment is the subject of current study. In this regards, the temperature of various electrolyte samples reduce to 5, 10, 15 and 20 °C and hold at different times without any turbulency. Experimental results reveal that decreasing the temperature of the electrolyte, facilitate the deposition of As and Sb in the form of AsO5Sb, AsO4Sb and As2O3 as the white precipitate at a critical time. Also, in the case of the electrolyte retention times exceed than the critical time, the copper content of electrolyte precipitate as blue phase. Typically, it is possible to remove 27 wt.% of Sb and 6 wt.% of As by... 

The kinematics information from imaging, if combined with optimization-based biomechanical models, may provide a unique platform for personalized assessment of trunk muscle forces (TMFs). Such a method, however, is feasible only if differences in lumbar spine kinematics due to differences in TMFs can be captured by the current imaging techniques. A finite element model of the spine within an optimization procedure was used to estimate segmental kinematics of lumbar spine associated with five different sets of TMFs. Each set of TMFs was associated with a hypothetical trunk neuromuscular strategy that optimized one aspect of lower back biomechanics. For each set of TMFs, the segmental... 

Properties of melt processed polyamide 66 (PA66)/multiwalled carbon nanotube composite were first characterized experimentally. The experimental results exhibited the formation of crystalline layer around the nanotubes and a considerable enhancement in mechanical properties by incorporation of multiwalled carbon nanotube up to 1 wt%. Mechanical properties were analyzed in terms of structural parameters using micromechanical models proposed in this study. It was suggested that the mechanical properties were greatly dominated by crystalline layer and nanotube length. It was also deduced that the melt mixing process caused a significant nanotube breakage restricting further enhancement of... 

The present study was an attempt to examine the effects of carbon and cellulose fibers on the tribological characteristics of rubber-based friction materials (RBFMs). A fiber free RBFM as a reference material and a series of fiber included RBFMs at different volume fractions were prepared by two-roll mill. The friction tests were per-formed at different sliding velocities and various drum temperatures. The mechanical properties and surface microstructure of friction specimens were also examined. It was revealed that the carbon fiber infiuences slightly the coefficient of friction (COF) of RBFM but it improves the wear resistance and the fade behavior considerably. It reduces the drum... 

This study deals with the thermal conductivity of rubber-based composite friction materials used in railroad vehicles. Based on a commercially available railroad friction material, called here base material (BM), various friction materials containing different thermally conductive fillers (Cu, brass, Al, Al2O3 and talc) are fabricated and then their thermal conductivities are measured at various contents of the fillers. Addition of the thermally conductive fillers causes an increase in thermal conductivity of the friction material from 0.48 up to 5.8 W/m K, depending on the type and content of the filler. In addition, the experimental results reveal that the thermal conductivity of the... 

Despite extensive studies on electrorefining to remove impurities from copper production units, bleeding electrolytes is the most popular method for controlling impurities due to low operating costs. A controlled cooled-reheat cycle was used to remove impurities in industrial electrolytes of Khatoon Abad copper company. Phase identification and physical study were done by the XRD, SEM, TEM, and FTIR techniques. The results confirmed the possibility of the removal of 23 wt% Ni, 26 wt% Sb, 2.4 wt% As and convention of 6 wt% of As5+ to As3+ at cooled-reheat cycle. © 2022 The Author(s)  

Nanosilica in different grades are used for producing rubber nanocomposites based on natural rubber (NR) and styrene-butadiene-rubber (SBR) blends benefiting from appropriate mechanical properties. This study aimed to introduce recycled nanosilica (RNSiO2) extracted from lead-acid battery separator wastes as a new nanosilica filler to prepare rubber nanocomposites with appropriate mechanical and aging properties in a sustainable manner. Using RNSiO2, vulcanized nanocomposites were prepared based on NR/SBR blends (RT20 and RA20 samples) in the presence of Irganox 1010 as a hindered phenolic antioxidant. An increasing trend was observed in modulus, tensile strength, tear strength, and hardness... 

Various models have been applied composed of the Peng-Robinson equation of state (PR-EoS) and the Soave-Redlich-Kwong equation of state (SRK-EoS) associated with three mixing rules including the following: Wong-Sandler (WS), van der Waals one (vdW1), and van der Waals two (vdW2) for phase behavior modeling of mixtures of supercritical CO2+different ionic liquids in vapor-liquid equilibrium (VLE) region. It has been found that the PR EoS implying the WS mixing rule can be used as a reliable thermodynamic model to perform a thermodynamic consistency test on the experimental data of phase behaviors of the supercritical CO2+ionic liquid systems (19 commonly-used ionic liquids have been studied).... 

The kinematics information from imaging, if combined with optimization-based biomechanical models, may provide a unique platform for personalized assessment of trunk muscle forces (TMFs). Such a method, however, is feasible only if differences in lumbar spine kinematics due to differences in TMFs can be captured by the current imaging techniques. A finite element model of the spine within an optimization procedure was used to estimate segmental kinematics of lumbar spine associated with five different sets of TMFs. Each set of TMFs was associated with a hypothetical trunk neuromuscular strategy that optimized one aspect of lower back biomechanics. For each set of TMFs, the segmental... 

Leaving an imprint: Hierarchical protein imprinting starting from wide-pore silica modified with a submonolayer of adsorbed protein (IgG or HSA) leads to an inverse polymeric replica of the silica template that features highly accessible protein-complementary binding sites (see picture). The resulting poly(acrylamide) beads (PIgG or PHSA) feature high binding capacities and can be used to selectively capture the proteins HSA and IgG from blood serum  

A single-chip Integrated circuit of 3.3 V/1 W class-D high fidelity and high efficiency audio power amplifier is presented in this paper. The design has been done using a 3.3 V/0.25 /spl mu/m CMOS process. The maximum output power is 1 W before the amplifier saturates. The THD+N at 0.5 W output power is below 0.03% and efficiency is better than 90% thanks to the careful design of the output stage. The dynamic range is more than 100 dB suitable for high fidelity audio applications. A single-loop single-bit third order sigma-delta modulator is used to generate the PWM signal from input audio signal. The PWM signal is then filtered at the output with a second order low pass filter external to...