Sharif Digital Repository

A continuum theory is employed to numerically study the equilibrium orientation and defect structures of a circular cylindrical particle with flat ends under a homeotropic anchoring condition in a uniform nematic medium. Different aspect ratios of this colloidal geometry from thin discotic to long rodlike shapes and several colloidal length scales ranging from mesoscale to nanoscale are investigated. We show that the equilibrium state of this colloidal geometry is sensitive to the two geometrical parameters: aspect ratio and length scale of the particle. For a large enough mesoscopic particle, there is a specific asymptotic equilibrium angle associated to each aspect ratio. Upon reducing the... 

In recent years, the technological advancement of supercapacitors has been increasing exponentially due to the high demand in electronic consumer products. As so, researchers have found a way to meet that demand by fabricating graphene. As developments are made toward the future, two big advancements to be made are large-scale fabrication of graphene and fabricating graphene as a flexible electrode. This would allow for use in larger products and for manipulation of the unique properties of graphene to accommodate superior design alternatives. While large scale production is still mentioned, this review is specifically focusing on different methods used to fabricate graphene as a flexible... 

Graphene nanoplatelets with lateral dimensions of ∼50-200 nm and thicknesses <2 nm were utilized for the extraction of nucleic acids (NAs) from eukaryotic and prokaryotic cells. The graphene nanoplatelets (both chemically exfoliated graphene oxide nanoplatelets and hydrazine-reduced graphene oxide nanoplatelets) successfully extracted plasmid DNA (pDNA) from Escherichia coli bacteria, comparable to a conventional phenol-chloroform (PC) method. Furthermore, it was found that the yield of graphene nanoplatelets in genomic DNA (gDNA) and RNA extractions from embryonic stem cells (ESCs) was also comparable to the yield of the conventional methods. The effects of the graphene nanoplatelets on... 

In this study, the effect of through-thickness shear (TTS) stress has been examined on the prediction of forming limit diagrams (FLDs). Determination of the FLD is based on the Marciniak–Kuczynski (M–K) model with some modifications on the stress states for consideration of the TTS stress effects. For solving the equations, the Newton–Raphson method has been used. Furthermore, the Nakazima test has been simulated to investigate the stress state which occurs in the sheet during the test. Results showed that the formability of sheet metal could be better as the through-thickness stress increased. Also, implementation of TTS stress in the present model, the corresponding FLD has better... 

In this study, the effect of through-thickness shear (TTS) stress has been examined on the prediction of forming limit diagrams (FLDs). Determination of the FLD is based on the Marciniak–Kuczynski (M–K) model with some modifications on the stress states for consideration of the TTS stress effects. For solving the equations, the Newton–Raphson method has been used. Furthermore, the Nakazima test has been simulated to investigate the stress state which occurs in the sheet during the test. Results showed that the formability of sheet metal could be better as the through-thickness stress increased. Also, implementation of TTS stress in the present model, the corresponding FLD has better... 

In this study, the effect of through-thickness shear (TTS) stress has been examined on the prediction of forming limit diagrams (FLDs). Determination of the FLD is based on the Marciniak–Kuczynski (M–K) model with some modifications on the stress states for consideration of the TTS stress effects. For solving the equations, the Newton–Raphson method has been used. Furthermore, the Nakazima test has been simulated to investigate the stress state which occurs in the sheet during the test. Results showed that the formability of sheet metal could be better as the through-thickness stress increased. Also, implementation of TTS stress in the present model, the corresponding FLD has better... 

In this paper, sliding friction and wear behaviors of gray cast iron A35 and white cast iron manufactured by quenching from the same cast iron in water were studied and compared by employing pin-on-disk wear tests. Microstructure of the worn surfaces before and after the wear tests were investigated by optical microscope observations. These images show that flakes separated from the surface in gray cast iron due to delamination process, while in white cast iron, the separation of materials from its surface is in the form of powder. In addition, the gray cast iron had higher graphite volume fraction with Type-A graphite flake morphology. The results show that white cast iron has less rate of... 

Topological defects are interesting phenomena which can be observed in ordered phases such as oriented active fluids or nematic liquid crystals. Topological defects are determined by the overall structure of the director field in an active fluid in nematic phase and by exerting force to the units of the active particles they can interact or cause motion in the environment. Studying them as particles with dynamical equations, instead of studying the director field of the nematic environment, would provide us the power to study the characteristics of their motion. The equations of motion for multi-defect systems have been previously studied and in this work we focus on the chaotic properties... 

IP core reuse is popular for designing and implementing complex systems, because reuse of already provided blocks decreases design time and so diminishes productivity gap. Moreover, as system-level design methodologies and tools emerge for embedded system design, it is useful to have a shift from Register Transfer Level to system-level models for IP cores employed for implementation of hardware parts of the system. In this paper, we propose a C++ model for hardware IP cores that can be adopted as a standard for delivering IPs at a high level of abstraction, suitable for object-oriented system-level design methodologies. Next, we extend our system-level synthesizer in order to integrate IP... 

Hantzsch 1, 4-dihydropyridines (1,4-DHPs) can be oxidized to the corresponding pyridine derivatives by thallium triacetate in high yields  

Alterations in the structure of a magnetron, e.g., the A6 relativistic magnetron, are proposed, which considerably increase the device's build-up speed. We cover the magnetron vane surfaces with semiconductor layers of nonzero electric conductivity, with an exact geometrical design. Semiconductor layers with considerable mechanical strength also provide excellent shielding for the vanes against the high-energy relativistic electrons' bombardment. The novel structure introduces several new free parameters to the magnetron design procedure and considerably increases the design flexibility. A multistage exact optimization procedure, performed by extensive computer simulations, shows that... 

In this paper, by using first-principle density functional theory (DFT) combined with non-equilibrium Green's function (NEGF), thermally induced spin current in zigzag and armchair Antimonene Nanoribbon (SbNR) is investigated. Also, we obtain higher spin current in Armchair nanoribbon (ANR) than zigzag nanoribbon (ZNR), because the start energy of transmission for ANR is closer to the Fermi level than ZNR. The results show that the device has a perfect spin Seebeck effect under temperature difference without gate voltage or bias voltage. For the ANR configuration, the competition between spin up holes and spin down electrons leads to negative differential behavior of charge current, which is... 

In this paper, thermally induced spin current in graphene-antimonene heterostructure is investigated using first-principle density functional theory (DFT) combined with the non-equilibrium Green’s function (NEGF) method. We obtain a higher spin current in the graphene-antimonene heterostructure (Gr-Sb) than in the graphene zigzag nanoribbon (GrZNR). The current versus source temperature shows negative differential behavior. Also, the results show that graphene-antimonene heterostructure's figure of merit coefficient could be ZT = 37 ×10 - 3 in the energy range – 0.5 eV < E < 0.5 eV, while its value for monolayer graphene is about 4000 times less. These results show that the figure of merit... 

The preparation of microcapsules containing perphenazine by solvent evaporation using ethyl cellulose is described. The microparticles are formed after solvent evaporation and polymer precipitation. The drug was dissolved in a polymer solution and emulsified into an aqueous phase to form microcapsules. To study the effects on particle size, encapsulation efficiency and morphology, three different molecular weights of ethyl cellulose (Mw=47000, 71000 and 99000) were used. Covalent bonding of drugs to polymers via hydrolytically or enzymatically cleavable covalent bond was achieved for sustained drug delivery. The release rate of perphenazine from these systems was investigated  

Considering the lipid concentration and side effects regarding the stents used by surgeons, a new heart stent model is proposed. In the new stent, a few piezo plates are designed and attached to the stents by which release of the lipids can take place due to the applied alternative voltages. Due to the vibrations of small-scale piezoelectric plates, the deposition of low-density-lipoproteins (LDL) floating in the blood flow in the coronary arteries is prevented. Small-scale effects are considered using nonlocal elasticity theory, and the interaction between fluid and solid is modeled using the Navier-Stokes equation. The effect of fluid parameters as well as applied voltage and geometry... 

Business intelligence (BI) is a managerial concept helping managers and organizations to manage information and make factual decisions. Some have introduced Business Intelligence as a process of turning data into information and then into knowledge. This concept has become a popular trend for businesses interested in adding value to their decision making processes. Measurement of maturity in implementing Business Intelligence process in organizations is considered a critical issue. Business intelligence like software development is a process, which expressed in terms of components such as artifacts and workflows. Capability Maturity Model Integrated (CMMI) is developed to define different... 

Given a social network modeled as a weighted graph GG, the influence maximization problem seeks kk vertices to become initially influenced, to maximize the expected number of influenced nodes under a particular diffusion model. The influence maximization problem has been proven to be NP-hard, and most proposed solutions to the problem are approximate greedy algorithms, which can guarantee a tunable approximation ratio for their results with respect to the optimal solution. The state-of-the-art algorithms are based on Reverse Influence Sampling (RIS) technique, which can offer both computational efficiency and non-trivial (1-1/e-ϵ)-approximation ratio guarantee for any epsilon >0ϵ>0.... 

We study the problem of experiment design to learn causal structures from interventional data. We consider an active learning setting in which the experimenter decides to intervene on one of the variables in the system in each step and uses the results of the intervention to recover further causal relationships among the variables. The goal is to fully identify the causal structures with minimum number of interventions. We present the first deep reinforcement learning based solution for the problem of experiment design. In the proposed method, we embed input graphs to vectors using a graph neural network and feed them to another neural network which outputs a variable for performing... 

One of the key objectives in many fields in machine learning is to discover causal relationships among a set of variables from observational data. In linear non-Gaussian acyclic models (LiNGAM), it can be shown that the true underlying causal structure can be identified uniquely from merely observational data. The DirectLiNGAM algorithm is a well-known solution to learn the true causal structure in a high dimensional setting. DirectLiNGAM algorithm executes in a sequence of iterations and it performs a set of comparisons between pairs of variables in each iteration. Unfortunately, the runtime of this algorithm grows significantly as the number of variables increases. In this paper, we... 

The depth of anaesthesia estimation has been of a great interest in recent decades. In this paper we present a new methodology to quantify the depth of anaesthesia by quantifying the power-law correlations of the EEG signal. Extraction of useful information about the nonlinear dynamics of the brain during anaesthesia has been proposed with the optimum fractal scaling exponent. This optimum solution is based on the best domain of box sizes in the detrended fluctuation analysis (DFA) algorithm which have meaningful changes at different depth of anaesthesia. The experimental results confirm that our new algorithm on the raw EEG data can clearly discriminate between aware to moderate and deep...