Sharif Digital Repository

In many industrial processes there is an urgent need for flocculation of suspensions that can’t flocculate easily through the time so flocculants are wildly used in these industries. Polymeric flocculants because of less needed dose are economically used. Polymeric flocculants divided to three categories: nonionic, anionic and cationic those are almost from polyacrylamide group. Studying mechanisms of flocculation, one of the main factors that enhance flocculation is molecular weight of polymer. Hence one of the goals of this work is to improve molecular weights of synthesized polymers as much as possible that is followed by viscometery, NMR, DSC and FTIR studies and ended with jar test.... 

Josephson junctions are the basic elements of superconducting technology. They play the same role of p-n junctions in semiconductor technology. Here, we investigated on the optical responses of the fabricated Josephson junctions in order to gain high sensitive optical sensors. The emission has both thermal and non-thermal effect on the current-voltage characteristics of the junctions. While the bolometric effect is the result of slight changes in the bias temperature of device, the non-thermal effect is due to depairing of Cooper pairs and generation of quasi-particles, which is dominant in temperatures far below TC especially in the case the superconducting layer is optically thin. In this... 

In this research application of Ionic Polymer Metal Composite (IPMC) as actuator in a deformable ring capable of locomotion is studied. Such a deformable ring moves as a result of gravitational force acting on its body when its shape changes. A deformable robot made of IPMC can be used in exploration, search and rescue missions in future, where using conventional robots with rigid bodies and actuators is impossible. Large deformation induced by small stimulating voltage, low stiffness and the sensing characteristics that in future work can be used in feedback control make IPMC a good choice for such an application. In this work first a model for IPMC is introduce that can be used in... 

The discovery of Iron-based superconductors with maximum transition temperature of 56 Kelvin and High critical magnetic field of the order of 50T at temperature 20K has created evolution in different fields of superconductivity including practical issues. BaFe2As2 family is one of the most important compounds of Iron-based superconductors and with different doping elements for instanse elements of the first column like Potassium inters superconducting state with critical temperature of 36K.
The purpose of this thesis is to localize the technology of making this compound in Iran which no project has been done in this field in the country before. In this thesis manufacturing, Optimization... 

The main purpose of this theses is to synthesize graphene by chemical vapor deposition (CVD) of a hydrocarbon gas such as methane on the nickel foam substrate and then to characterize this kind of graphene. Graphene is a single layer of carbon atoms, discovered in 2004, which has led mankind to new eras in all fields by its extraordinary features such as extra high electron mobility, high thermal conductivity, excellent mechanical strength, optical transparence and extra high specific surface. The advantage of this method compared to other methods is that the graphene generated has a better structural quality. Graphene foam firstly, because of the continuity of the foam structure, has better... 

Due to the increasing use of data storage systems and volume of digital data, fast information access and retrieval has significant effect on performance of storage-bound systems. Operating systems utilize the spare space in the main memory as a cache to speed up access to the storage subsystem. Due to the large performance gap between hard disk and main memory, any improvement in this caching layer can greatly affect the performance of the entire system. Page replacement algorithms are one of the important mechanisms in the virtual memory management layer. Several algorithms have been proposed for the eviction of pages from the virtual memory cache and few of them have also been implemented... 

UF membranes are widely used in various industries now, a major type of these membranes are ceramic membranes which are resistant to high temperatures and corrosive fluids. In this thesis we developed an anisotropic UF ceramic membrane based on 20nm TiO2 nanoparticles on a prous sustrate. We had two major challenges, the first one was to find a suitable prous substrate and the second one was to find an appropriate coating method. Our main task was to optimise the process conditions to achive a crackless and uniform membrane layer with minimal ups and downs. Lots of coating methods and TiO2 inks have been tried, finally we used a coating method which we called it “Soft Blade Coating”, with... 

In this study, at first the V2O5 spent catalysts were characterized. The aim was to identifying whether these catalyst may be regenerated. Then, for feasibility study of them, three methods were applied: washing, diffusion and milling the spent catalysts for their subsequent reproduction. A variety of techniques such as XRD, XRF, AAS, TPR and TPO were applied in order to identify factors contributing in vanadium pentoxide catalysts deactivation. The results showed that approximately all of pollutants caused their performance deterioration, while they still have some active phases. Then, the polluted catalysts were washed (their yield increased from 43% to 72.2%). In the underside of the... 

Emerging Solid State Drives (SSDs) have performance advantages over traditional Hard Disk Drives (HDDs). Higher price per capacity and limited lifetime, however, prevents enterprise data centers to entirely replace HDD-based storage subsystems with SSDs. Thus,SSD-based caching has been widely employed in data centers to benefit from higher performance of SSDs while minimizing overall cost. Input/Output (I/O) workloads exhibit unpredictable and highly random behavior which makes conventional algorithms such as Least Recently Used (LRU) not able to provide high hit ratio as they employ linear localities.In addition to poor performance, such algorithms also shorten SSD lifetime with unnecessary... 

Cancer is the second leading cause of death among humans as one of the major human concerns. More than 500,000 people die of cancer each year in the United States alone. Cancer mortality is mainly due to cancer metastasis. Metastasis is the escape of cancer cells from a primary tumor, the circulation of cells in the circulatory system (CTSs), the penetration of/from vessel wall, and the formation of a secondary tumor. It is still not clear how the cells survive in the circulatory system, along with the mechanical pressures and stresses that exist in the body's capillary channals. In this study, a microcirculation model for circulating cells with barriers was designed and constructed by the... 

Isolation and characterization of circulating tumor cells (CTCs) found in blood samples of cancer patients have been considered as a reliable source for cancer prognosis and diagnosis. A new continuous microfluidic platform has been designed in this investigation for simultaneous capture and characterization of CTCs based on their deformability. The deformability-based chip (D-Chip) consists of two sections of separation and characterization where slanted weirs with a gap of 7 μm were considered. Although sometimes CTCs and leukocytes have the same size, the deformability differs in such a way that can be exploited for enrichment purposes. MCF7 and MDA-MB-231 cell lines were used for the... 

In this study, a new bioink was introduced for the production of tubular tissue structures for cardiac tissue engineering by bioprinter using the FRESH (Freeform Reversible Embedding of Suspended Hydrogels) method. The novel bioink that we used was a combination of cardiac extracellular matrix (cECM) and oxidized alginate. The cardiac extracellular matrix was used to increase the biomimetic of the printed structures to the actual tissue of the body, and also to create sites for cell adhesion, and to improve cell growth and survival. We used alginate oxide (oxidation degree: 5%) to increase the mechanical properties of the tissue. Alginate oxidation has been due to extracellular matrix (ECM)... 

This study presents a comprehensive investigation into the characterization of three distinct homogeneous multilayer self-standing thin films, composed of stacked reduced graphene oxide (rGO) planes, which were synthesized using a modified Hummer’s method. In order to investigate their structural, electrical, and optical properties, the samples were characterized by field emission scanning electron microscopy (FESEM), Raman spectroscopy, four-point probe measurements, Impedance measurements, Fourier-transform infrared spectroscopy (FTIR), and Time domain Terahertz Spectroscopy (TDS). The FESEM images obtained from the samples reveal a smooth sheet-like surface with few wrinkles.... 

Nowadays, design and development of high performance storage subsystems have been a crucial step in data-intensive computer systems. One of the solutions for improving the overall performance of data storage systems is to use emerging flash-based memories as an I/O cache. OpenCAS, EnhanceIO, and DM-cache are well-known I/O cache modules with different architectures. None of the previous works studied the performance of these I/O cache modules in detail. This research evaluates the performance of I/O cache modules under the real and synthetic workloads and tries to analyze the observed behavior based on their high-level architecture. In addition, we propose some insights about how to improve... 

The lifespan of hard disks greatly affects their performance and reliability. Ensuring the freshness of disks during the procurement process for hardware manufacturing companies is crucial for maintaining efficient production systems. Predicting the approximate lifespan of hard disks involves analyzing their characteristics and operational history. Relying solely on SMART reports for estimating disk lifespan is not reliable due to the potential firmware tampering. Previous studies have primarily focused on SATA disks, investigating the relationship between failures and SMART parameter values, while neglecting SAS disks. However, in this research, we collected SMART reports from approximately... 

plasma characterization has become an essential tool for characterization of etching process in fabrication of nano-electronic devices. The existing methods, such as Langmuir probe and interferometry, have shown drawbacks including disturbing the plasma and sensitivity to mechanical and thermal stability of the measuring systems. In recent years, due to the scale down of microelectronic devices and increase of their sensitivity to disturbance in the plasma etching process, a demand for measuring methods offering less disturbance has arisen. Plasmonic structures, owing to their unprecedented field enhancement and confinement, have been extensively studied. Their sub-wavelength dimensions,...