Sharif Digital Repository

Surface tension driven passive micro-pumping relies mainly on the surface tension properties. To have control over surface tension driven passive micro-pumps (STD-PMPs), it is essential to understand the physical background of the fluid flow in these pumps. Hence, the purpose of this work is to give an exploration of the flow physics of a STD-PMP. In this regard, computer simulation is used to give detailed information about the flow pattern and physical phenomena at different conditions. To this end, a droplet of water, with a specified diameter, is placed onto an entry port connected to another droplet at the exit port via a microchannel. The results indicate that the pumping process, in... 

The present study provides an accurate simulation of velocity and temperature distributions of inhalation thermal injury in a human upper airway, including vestibule, nasal cavity, paranasal sinuses, nasopharynx, oropharynx, larynx, and upper part of main bronchus. To this end, a series of CT scan images, taken from an adult woman, was used to construct a three dimensional model. The airway walls temperature was adjusted according to existing in vivo temperature measurements. Also, in order to cover all breathing activities, five different breathing flow rates (10, 15, 20, 30, and 40. l/min) and different ambient air temperatures (100, 200, 300, 400, and 500. °C) were studied. Different flow... 

Designing meta-materials and cellular solids with biomimetic structures has received increasing attention in the past few years partially due to advances in additive manufacturing techniques that have enabled the fabrication of advanced materials with arbitrarily complex microarchitectures and novel functionalities. To impact on this trend, it is essential to develop our understanding about the role of microstructure on mechanical responses of these structures. Although a large literature exists on the general subject, the role of microstructure on the post-yield instability is not yet adequately documented. This research introduces a numerical approach to study the post-yield instability in... 

Purpose: Hexagonal honeycombs with meso-metric cell size show excellent load bearing and energy absorption potential, which make them attractive in many applications. However, owing to their bend-dominated structure, honeycombs are susceptible to deformation localization. The purpose of this study is to provide insight about shear band propagation in struts of 3D-printed honeycombs and its relation to the achieved macroscopic mechanical behavior. Design/methodology/approach: Hexagonal honeycombs and unit cell models are 3D-printed by fused deposition modeling (FDM). The samples are exposed to compression loading and digital image correlation technique and finite element analyses are... 

The current research focuses on suggesting a new potential application of polymeric materials for capacitor applications by focusing on polystyrene (PS)/ethylene-α-octene copolymer (EOC) blends. Polymeric materials have high dielectric strength (≈ 200 for PS), good processability, and flexibility. However, their low dielectric constants make them not suitable for capacitor applications. Therefore, suggesting a method for enhancing their dielectric constant accompanied by low tan δ proposes an excellent substitute for commonly used ceramic dielectrics. The current article investigates the control of the dielectric properties of PS/EOC blends by manipulating the graphene nanoplatelets (GNPs)... 

A laboratory-scale multistage anaerobic biofilm reactor of three compartments with a working volume of 54-L was used for treating a synthetic medium-strength wastewater containing molasses as a carbon source at different influent conditions. The start-up period, stability and performance of this reactor were assessed at mesophilic temperature (35 °C). During the start-up period, pH fluctuations were observed because there was no microbial selection or zoning, but as the experiment progressed, results showed that phase separation had occurred inside the reactor. COD removal percentages of 91.6, 91.6, 90.0 and 88.3 were achieved at organic loading rates of 3.0, 4.5, 6.75 and 9.0 kg COD/m3 day,... 

This study presents an electrochemical procedure for synthesizing graphene oxide (GO) nanosheets in a diluted acidic medium (0.05 M), featuring 100% synthesis yield. Characterization results revealed that the synthesized GO in this approach exhibits a low XRD peak position (around 10°) and a C/O ratio of 2.9, offering higher surface functionality than conventional electrochemical methods reported in the literature. We also demonstrated the tunability of the GO's surface functionality by manipulating the synthesis parameters, such as electrolyte concentration and synthesis time, offering flexibility that surpasses the constraints often seen in chemical methods. Additionally, it was observed... 

Study of the plastic deformation in polymeric honeycombs can pave the way for understanding the deformation localization in more complex cellular structures, which have received progressive attention in the past few years. This study compares the strain localization in deforming honeycombs made by two cost-effective 3D-printing technologies. Hexagonal honeycombs and their unit cell models were 3D-printed by both PolyJet™, using a photo-crosslinkable polymer, and fused deposition modeling (FDM) using a thermoplastic material. The state of the art digital image correlation (DIC) technique was employed as the experimental route in order to calculate the strain field during the deformation of... 

A set of complementary experiments are used for the first time to elucidate the interrelation between the mechanical properties, the strain field, and the free volume evolution during non-homogenous compression of aglassy polymer. Two sets of quenched and annealed polystyrene samples, having different free volume histories, are notched and exposed to compression. The variation of both the strain field and the free volume are measured on a microscopic scale via digital image correlation in case of strain and Doppler broadening spectroscopy of positron annihilation line in case of free volume measurements. Eventually, the interplay between the local evolution of free-volume, the local strain... 

This laboratory research was carried out to evaluate the performance of a multistage anaerobic biofilm reactor, with six compartments and a working volume of 70 L, for the treatment of a strong synthetic nitrogenous and high-strength wastewater at an operational temperature of 26 ± 0.5 °C. Initially, the performance of the reactor was studied when subjected to an increase in the hydraulic retention time (HRT) at a constant influent COD concentration of 10,000 mg/L. Five different HRTs were studied: 0.25, 0.67, 1, 3 and 5 days, which were equivalent to 6, 16, 24, 72 and 120 h, respectively. By increasing the HRTs from 6 h to 1 day, COD and BOD removal efficiencies were increased from 63% to... 

Prediction of reaction yield as the most important characteristic process of a slurry polymerization industrial process of propylene has been carried out. Stacked neural network as an effective method for modeling of inherently complex and nonlinear systems-espe-cially a system with a limited number of experimental data points-was chosen for yield prediction. Also, effect of operational parameters on propylene polymerization yield was modeled by the use of this method. The catalyst system was Mg(OEt)2/DIBP/TiCl 4/PTES/AlEt3, where Mg(OEt)2, DIBP (diisobutyl phthalate), TiCl4, PTES (phenyl triethoxy silane), and triethyl aluminum (AlEt3) (TEAl) were employed as support, internal electron... 

Long term evolution (LTE)-advanced aims the peak data rates in excess of 3 Gbps for the next generation wireless communication systems. Turbo codes, the specified channel coding scheme in LTE, suffers from a low-decoding throughput due to its iterative decoding algorithm. One efficient approach to achieve a promising throughput is to use multiple Maximum a Posteriori (MAP) cores in parallel, resulting in a large area overhead, a big drawback. The scaled Max-log MAP algorithm is a common approach to implement the MAP algorithm due to its efficient architecture with its acceptable performance. Although many works have been reported to reduce the area of the MAP unit, an efficient VLSI... 

Long-term evolution (LTE) is aimed to achieve the peak data rates in excess of 300 Mb/s for the next-generation wireless communication systems. Turbo codes, the specified channel-coding scheme in LTE, suffer from a low-decoding throughput due to its iterative decoding algorithm. One efficient approach to achieve a promising throughput is to use multiple maximum a posteriori (MAP) cores in parallel, resulting in a large area overhead. The two computationally challenging units in an MAP core are α and β recursion units. Although several methods have been proposed to shorten the critical path of these recursion units, their area-efficient architecture with minimum silicon area is still missing.... 

5-th generation mobile networks aim the peak data rates in excess of few Gbs, which may appear to be challenging to achieve due to the existence of some blocks such as the turbo decoder. In fact, the interleaver is known to be a major challenging part of the turbo decoder due to its need to the parallel interleaved memory access. LTE uses Quadratic Permutation Polynomial (QPP) interleaver, which makes it suitable for the parallel decoding. In this paper, a new property of the QPP interleaver, called the correlated shifting property, is theoretically proved, leading to a fully scalable interleaver and a low-complexity address generator for an arbitrary order of parallelism. The proposed... 

Processor allocation in todays many core MPSoCs is a challenging task, especially since the order and requirements of incoming applications are unknown during design stage. To improve network performance, balance the workload across processing cores, or mitigate the effect of hot processing elements in thermal management methodologies, task migration is a method which has attracted much attention in recent years. Runtime task migration was first proposed in multicomputer with load balancing as the major objective. However, specific NoC properties such as limited amount of communication buffers, more sensitivity to implementation complexity, and tight latency and power consumption constraints... 

Processor allocation in todays many core MPSoCs is a challenging task, especially since the order and requirements of incoming applications are unknown during design stage. To improve network performance, balance the workload across processing cores, or mitigate the effect of hot processing elements in thermal management methodologies, task migration is a method which has attracted much attention in recent years. Runtime task migration was first proposed in multicomputer with load balancing as the major objective. However, specific NoC properties such as limited amount of communication buffers, more sensitivity to implementation complexity, and tight latency and power consumption constraints... 

A structure is suggested for spasing. The presented surface plasmon amplification by stimulated emission of Radiation (SPASER) is made up of a graphene nanosphere, which supports localized surface plasmon modes, and a quantum dot array, acting as a gain medium. The gain medium is pumped by an external light source. Since all the plasmons are carried on a graphene platform, the structure features coherent surface plasmons with high confinement and large life time. All the structures are analyzed theoretically using full quantum mechanical description. The main advantage of the proposed SPASER is its simple tuning capability of changing graphene's Fermi level, which is performed by either...