Sharif Digital Repository

Pulse Repetition Interval (PRI) Modulation Detection is an important subsystem of a typical electronic warfare support system. In this paper, a robust, fast, and well designed structure for detection of simple and complex PRI modulations based on statistical and sequential analysis of Pulse Repetition Interval (PRI) is proposed. Accuracy and robustness of the technique against electromagnetic noise are demonstrated via simulations  

In this paper, the compatibility of various combinations of numerical schemes for the solution of flow and transport equations in porous media is studied and the possible loss of accuracy and global mass conservation are investigated. Here, the flow equations are solved using three popular finite element methods including the Standard Galerkin (SG), Discontinuous Galerkin (DG) and Mixed Finite Element (MFE) methods among which only the DG method possesses the local conservation property. Besides, the transport of a scalar variable which is governed by a convection-diffusion equation is studied in conjunction with the flow equations. The transport equation is solved using both the Streamline... 

Particle transport and deposition in a channel flow with elliptic obstruction is studied. Numerical simulation of fluid flow is performed using two-dimensional lattice Boltzmann method, while one-way coupling Lagrangian method for particle tracking is used. Standard particles are injected in the inlet of the channel. Gravity, Drag force, Brownian forces, and the Saffman lift are considered in equation of particle motion. The influence of geometrical parameter, ellipse aspect ratio, is studied on dispersion and deposition of particles as well as the flow parameters, such as Reynolds number. In addition, the effect of particles size -particles of 0.01-10μm in diameter- on dispersion and... 

In aerospace applications structures weight is considered as a major performance parameter. One of the most effective manufacturing methods for weight reduction is superplastic forming. By this technique, not only the weight, but also the stress concentration, the cost, and the manufacturing time are noticeably reduced. Additionally, the components with complicated shapes could be formed in a single manufacturing step. Due to the wide demand for whiskers reinforced metal matrix composites (MMCs) in aerospace industries, many research works have been designed to extend the borders of superplastic forming to MMCs materials. In the present study, a 3-D symmetric micromechanical finite element... 

A pH-responsive drug delivery system based on core shell structure of mesoporous silica nanoparticle (MSN) and chitosan-PEG copolymer was prepared and characterized by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscope (SEM), and high-resolution transmission microscope (HR-TEM) techniques. In order to improve compatibility MSN and drug, mesoporous nanosilica was modified by 3-aminopropyl triethoxysilane. The release of erythromycin (a macrolide antibiotic) as a model drug was investigated in two pHs, 7.4 and 5.5  

Gas-phase acidities of nucleosides, combined with the knowledge of deprotonation sites, could improve our understanding of chemical reactions to biological systems. In this paper, we mainly focus our attention on the influence of cation coordination on acidities of multiple sites in cytosine nucleosides. The acidities of multiple sites in M +-L (where L represents cytosine nucleosides and M + is an alkali metal ion, including Li +, Na + and K +) complexes have been investigated theoretically, employing B3LY P6-311++G(d,p) basis sets. The geometrical characters, gas-phase acidities, sugar puckering and electronic properties of non-deprotonated and/or deprotonated complexes have been... 

Inverted pendulum (IP) has been broadly used to model locomotor systems. In this paper, we demonstrate that an IP-like model could simulate stable periodic handspring maneuvers with passive flight phases. The model is a 2-D symmetric rigid body which is merely controlled during the contact phase. To benefit from an open-loop sensorless strategy, the control policy is implemented only by an unvaried torque input. The system's dynamics is an example of nonlinear impulsive systems studied and analyzed by the Poincaré section method. The numerical results reveal that the stable periodic solutions are sufficiently robust for a broad range of the parameter space. © 2020 Elsevier Ltd  

In recent years, there has been increasing interest in damaged DNA and RNA nucleobases. These damaged nucleobases can cause DNA mutation, resulting in various diseases such as cancer. Alkylating agents are mutagenic and carcinogenic in a variety of prokaryotic and eukaryotic organisms. The present study employs density functional theory (DFT/B3LYP) with the 6-311++G(d,p) basis set to investigate the effect of chemical damage in O-alkyl pyrimidines such as O4-methylthymine, O2-methylcytosine and O 2-methylthymine. We compared the intrinsic properties, such as proton affinities, gas phase acidities, equilibrium tautomerization and nucleobase pair's hydrogen bonding properties, of these... 

Glutathione tripeptide (γ-glutamyl-cysteinyl-glycine) is a flexible molecule and its conformational energy landscape is strongly influenced by forming intramolecular hydrogen bond, its charge and the environment. This study employs DFT-B3LYP method with the 6-31+G (d,p) basis set to carry out conformational analysis of neutral, zwitterionic, cationic, and anionic forms of glutathione. In analyzing the structural characteristics of these structures, intramolecular hydrogen bonds were identified and characterized in details by topological parameters such as electron density ρ(r) and Laplacian of electron density Δ2 ρ(r) from Bader's atom in molecules theory. Charge transfer energies based on... 

It is possible to define multiresolution by reversing the process of subdivision. One approach to reverse a subdivision scheme appropriates pure numerical algebraic relations for subdivision using the interaction of diagrams (Bartels and Samavati, 2011; Samavati and Bartels, 2006). However, certain assumptions carried through the available work, two of which we wish to challenge: (1) the construction of multiresolutions for irregular meshes are reconsidered in the presence of any extraordinary vertex rather than being prepared beforehand as simple available relations and (2) the connectivity graph of the coarse mesh would have to be a subgraph of the connectivity graph of the fine mesh. 3... 

Density functional theory (DFT) calculations were performed at the B3LYP level with a 6-311++G(d,p) basis set to systematically explore the geometrical multiplicity and binding strength for complexes formed by Li+, Na+, and K+ with cytidine and 2′-deoxycytidine. All computational studies indicate that the metal ion affinity (MIA) decreases from Li+ to Na+ and K+ for cytosine nucleosides. For example, for cytidine the affinity for the above metal ions are 79.5, 55.2, and 41.8 and for 2′-deoxycytidine, 82.8, 57.4, and 42.2 kcal/mol, respectively. It is also interesting to mention that linear correlations between calculated MIA values and the atomic numbers (Z) of the above metal ions were... 

In this paper, we present a novel idea on actuation system in micropumps. The prominent goal of this paper is to propose and prove a mechanical actuation system which works in high frequency and has good ability in producing flow and pressure in micro actuation system. As like as other common micropumps, the proposed scheme is consisted of two check valves and an actuation space. The actuation space includes a volume of liquid in a chamber and a cylindrical membrane as the actuator. The main aspect of this idea is employment of buckling as a consequence of incensement of its internal pressure caused by temperature rising in the membrane. Rise of temperature is done by passing a controllable... 

Background: Angiogenesis inhibition research is a cutting edge area in angiogenesis-dependent disease therapy, especially in cancer therapy. Recently, studies on anti-angiogenic peptides have provided promising results in the field of cancer treatment. Methods: A non-redundant dataset of 135 anti-angiogenic peptides (positive instances) and 135 non anti-angiogenic peptides (negative instances) was used in this study. Also, 20% of each class were selected to construct an independent test dataset (see Additional files 1, 2). We proposed an effective machine learning based R package (AntAngioCOOL) to predict anti-angiogenic peptides. We have examined more than 200 different classifiers to build... 

The aim of this study was to evaluate the influence of bonding temperature and holding time on the metallurgical and mechanical properties for weld joints of 5 mm aluminum to copper using Sn interlayer. The bonding temperature varied from 500 to 600 °C whilst the holding time varied from 30 to 120 min under 8 MPa uniaxial load in 1 × 10−4 torr vacuum. The microstructure analysis, phase analysis and distribution of elements in the interface were performed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, and element map analysis. It was found that diffusion welding parameters had a significant effect on shear strength. The attained data of tensile strength tests showed... 

We present the zero temperature phase diagram of the bond alternating Ising chain in the presence of Dzyaloshinskii-Moriya interaction. An abrupt change in ground state fidelity is a signature of quantum phase transition. We obtain the renormalization of fidelity in terms of quantum renormalization group without the need to know the ground state. We calculate the fidelity susceptibility and its scaling behavior close to quantum critical point (QCP) to find the critical exponent which governs the divergence of correlation length. The model consists of a long range antiferromagnetic order with nonzero staggered magnetization which is separated from a helical ordered phase at QCP. Our results... 

Bromophenols are known as antioxidant radical scavengers for some biomolecules such as those in marine red alga. Full understanding of the role played by bromophenols requires detailed knowledge of the radical scavenging activities in probable pathways, a focus of ongoing research. To gain detailed insight into two suggested pathways, H-atom transfer and electron transfer, theoretical studies employing first principle quantum mechanical calculations have been carried out on selected bromophenols. Detailed investigation of the aforementioned routes revealed that upon H-atom abstraction or the electron transfer process, bromophenols cause an increase in radical species in which the unpaired... 

In this study synthesis of a drug delivery system (DDS) is described which has several merits over its counterparts. In order to synthesize this nano-carrier, graphene oxide nano-sheets are used to accommodate MCM-41 nanoparticles. Furthermore Fe3O4 nanoparticles are introduced to this nano-material to produce a traceable nanoparticle. Since cancerous tissues have lower pH than healthy tissues, pH-sensitive oligomers are attached to this nano-material. Finally the nano-carrier is wrapped by a biocompatible shell (PEGylated sodium alginate); this polymeric shell makes the DDS capable of a more controllable drug release. By measuring in vitro situation, ‘loading content%’... 

With the introduction of restructuring concepts to traditional power systems, a great deal of attention is given to the utilization of distributed generation. Since the integration of DG units has been known as an alternative for main grid as a resource for energy supply, the determination of optimal sizing and sitting is an important issue in the planning procedure of DG. This work presents a comprehensive multi-objective model for integration of distributed generations into a distribution network, regarding various technical, economical and environmental issues such as reduction of carbon dioxide emissions and investment & running costs while the bus voltages shall be kept within...