Sharif Digital Repository

Given the rapid growth of the population and the increasing demand for drinking water, along with the depletion of freshwater resources, the presence of heavy metals such as arsenic, cadmium, mercury, lead, and chromium in water sources is considered a serious threat to public health due to their bioaccumulation properties and potential carcinogenicity. In this study, the process of nanofiltration has been employed to remove these heavy metals. Nanofiltration is recognized as an effective method for water treatment due to its low energy consumption and high efficiency. The primary objective of this research is to enhance the physical and chemical properties of nanofiltration membranes... 

In this research, the numerical simulation of liquid jet ejecting for a series of elliptical orifices into gaseous phase with different aspect ratios, at Rayleigh flow regime and in a range of Weber numbers has been performed.
For simulations, the OpenFoam software was utilized, which its multiphase flow simulation solvers are based on volume of fluid (VOF) method. In order to achieve the most accurate results for axis-switching phenomenon and jet breakup length, the dynamic mesh refinement was used for all the examined cases. The results, which were validated with recent experimental and numerical works, indicate that jet breakup length raises by increasing Weber number from 20 to 300.... 

Direct metal deposition (DMD) process is an additive manufacturing technology that is rapidly gaining laser importance due to its various capabilities in applications such as coating, repairing high-value damaged parts, rapid prototyping and even production in small quantities. Among the equipment needed for this process, nozzle is perhaps the most important component because its performance affect the efficiency of powders trapped in the molten pool, and is crucial to the quality of the deposited layer. The existing nozzle designs can be categorized in two groups; lateral and coaxial nozzles; and the coaxial ones are divided into continuous and discontinuous types. Coaxial nozzles have... 

Optical Coherence Tomography (OCT) has a great potential to elicit clinically useful information from tissues due to its high axial and transversal resolution. In practice, an OCT setup cannot reach to its theoretical resolution due to imperfections of its components, which make its images blurry. The blurriness is different alongside regions of image, thus they cannot be modeled by a unique point spread function (PSF). In this paper, we investigate the use of solid phantoms to estimate the PSF of each sub-region of imaging system. We then utilize Lucy-Richardson, steepest descent (SD) and total variation (TV) based iterative deconvolution methods for mitigating occurred spatially variant... 

The hulls of various ships are exposed to the problem of biofoulings on the hull after a period of time due to use in the salt water environment of the sea and the existence of suitable conditions for the growth of marine plants, so that the ship after about one month of stopping in the port, in order to start the activity again, it is necessary to clean the hull from these biofoulings. The ship will be transported to the dry dock for cleaning only when it is heavily involved in biofoulings on the hull, and in the meantime, it must be periodically cleaned in water by other systems, including the diver and robotic systems.Using a robotic system to perform this operation has various... 

In this thesis, we have tried to study one of the most well known collective behavior phenomena known as the Wisdom of the crowd, from the perspective of statistical physics. In recent decades with the appearance of Social Networks and mass media, collective social phenomena have become a critical topic in the life of every human being. In the Wisdom of crowd phenomenon, the overall process is to ask the crowd’s opinion regarding a special topic and after aggregating the predicted values, the aggregated quantity is declared as the wisdom of the crowd. It has been observed that in some polls and elections, the result of the wisdom of crowd outperforms every individual of the group and in some... 

The current gold standard for clinical diagnosis of melanoma is excisional biopsy and histopathologic analysis. Approximately 15–30 benign lesions are biopsied to diagnose each melanoma. In addition, biopsies are invasive and result in pain, anxiety, scarring, and disfigurement of patients, which can add additional burden to the health care system. Among several imaging techniques developed to enhance melanoma diagnosis, optical coherence tomography (OCT), with its highresolution and intermediate penetration depth, can potentially provide required diagnostic information noninvasively.
an image analysis algorithm, "optical radiomic melanoma detection (ORMD)" has been presented which... 

This study examines how agricultural profitability affects rural-to-urban migration in Iran. Since this relationship may suffer from endogeneity problems such as reverse causality, the main strategy is to use an instrumental variable approach (two-stage least squares regression). The results show that higher agricultural profitability leads to more migration from rural areas to cities. Specifically, an increase of one million tomans in annual agricultural profit increases the rural-to-urban migration rate by about 0.03 percentage points, which is statistically significant at the 1% level. This suggests that many rural residents want to move to cities, but they need higher agricultural... 

Present work focuses on the influence of Heteroatom(s) on the bacisity of specific group of amines through the intramolecular hydrogen bonding. This group includes Aza-Crown Ethers specifically. We used Spartan and Gaussian packages to gain optimized structures for all compounds in order to explore the influence of the intramolecular hydrogen bonding on the bacisity of amines. All the gas phase optimizations and energy calculations were performed at the DFT/B3LYP/6-311++G(d,p) level of theory. The Hf/6-31+G(d,p) level was used for all single point calculations in the solution phase. As commonly used solvents in organic and biological reactions, the solution phase calculations were carried... 

Today, the importance of growth and its relation with the survival of the organization is well-known by all managers. However, path selection in this area seems extremely vague and difficult. The present theoretical research, conducted to help further clarify growth dimension characteristics, aims at considering possible growth paths for firms as well as examining required capabilities for each path. In this research, firm growth was studied from three different angles: value chain, product system complexity and the market. A relatively comprehensive categorization was made of organizational capabilities namely technological, managerial and networking and it was examined within dynamic and... 

Time delay generates exponential transcendental terms in characteristic equations. Subsequently, the applied methods are narrow to assess the stability map of delayed fractional-order systems with vanishing fractions. In this case, it is convenient to approximate these equations with its integer-order counterparts to design controllers or investigating features of the systems. But, delay can cause enormous differences between characteristic of these two equations. This study offers a method to survey analytically the stability of fractional-order time delayed linear time invariant systems with infinitesimal fractions. In this method, equations are transferred to an explicit expression which... 

In this project, conceptual and detailed designs of a knee prosthesis constraint testing machine were performed based on ASTM F1223-20 standard. Conceptual and detailed mechanical and electrical design of machine and parts were performed based on common engineering practice and standards. Parts were carefully manufactured and controlled for quality assurance. The machine was then assembled and checked for proof of performance. A plc program was written as machine software. A comprehensive user interface was coded on computer for performing various tests, which can command the machine and view the required data in a graphical environment. Finally, simple experiments were designed and... 

High-quality online services demand reliable and fast packet delivery at the network layer. However, clear evidence documents the existence of compromised routers in the ISP and enterprise networks, threatening network availability and reliability. A compromised router can stealthily drop, modify, inject, or delay packets in the forwarding path to launch Denial-of-Service, surveillance, man-in-the-middle attacks, etc. So researches tried to create intrusion detection methods to identify adversarial routers and switches. To this end, data-plane fault localization (FL) aims to identify faulty links and is an effective means of achieving high network availability. FL protocols use... 

Confining nematic liquid crystal between two curved boundary conditions while the nematic molecules have a degenerate planar anchoring leads to complex and beautiful textures of molecular disparagement(defect) in the bulk and on the surfaces. Such the liquid crystal shells are made with double-emulsion techniques in microfluidic devices have provided applications for micro-scale colloidal linkers.In this work, we have numerically minimized the elastic energy in one-constant approximation in present of Fournier’s degenerate surface potential with finite element method. The nematic shell is confined between two spherical surfaces that we have studied the final energies and their related...