Sharif Digital Repository

In recent years, development of the superelements has significantly influenced the analysis of structural dynamics. One of the common implementation of this element has been in the analysis of plates and shells. In this paper, application of superelements in the vibration analysis of orthotropic rectangular plates with different boundary conditions is considered, in which bending and in-plane displacements are also included. Results of this study indicate that there is a good agreement between single superelement and 625 elements using conventional methods © 2002 Published by Elsevier Science B.V  

Scheduling and Operation of Virtual Power Plants: Technical Challenges and Electricity Markets provides a multidisciplinary perspective on recent advances in VPPs, ranging from required infrastructures and planning to operation and control. The work details the required components in a virtual power plant, including smartness of power system, instrument and information and communication technologies (ICTs), measurement units, and distributed energy sources. Contributors assess the proposed benefits of virtual power plant in solving problems of distributed energy sources in integrating the small, distributed and intermittent output of these units. In addition, they investigate the likely... 

Since the beginning of industrial age the atmospheric concentration of greenhouse gases has been increased significantly due to excessive use of fossil fuels. An effective way for decreasing emission of greenhouse gases is injection of CO2 in geological formations. Moreover, from the reservoir engineering point of view, CO2 injection has been considered as a method of enhancing oil and gas recovery. While using CO2 for enhanced oil recovery (EOR) has been the subject of several studies in the past decades, enhanced gas recovery (EGR) has not been fully studied in the gas reservoirs, mainly because of high recovery factor of gas reservoirs and mixing of the reservoir gas and CO2. In this... 

Introduction: The COVID-19 pandemic has considerably affected human beings most of whom are healthcare workers (HCWs) combating the disease in the front line. Methods: This cross-sectional study aims to explore the effects of stress and anxiety caused by COVID-19 on the quality of sleep and life in HCWs, including physicians, nurses, and other healthcare staff. In this global study, we asked 1,210 HCWs (620 and 590 volunteers from Iran and European countries, including Germany, the Netherlands, and Italy, respectively), who age 21–70, to participate in the test. Several measures of COVID-related stress, anxiety, sleep, and life quality, including the 12-item General Health Questionnaire... 

In this research, two shake table experiments were conducted to study the effects of non-liquefiable crust layer and superstructure mass on the responses of two sets of 2 × 2 pile groups to liquefaction-induced lateral spreading. In this regard, an inclined base layer overlain by a very loose liquefiable layer was constructed in both models; while only in one model, a non-liquefiable crust layer was built. A lumped mass, being representative of a superstructure, was attached to the cap of one pile group in both models. The models were fully instrumented with various sensors, including acceleration, displacement, and pore water pressure transducers. Also, the piles were instrumented with pair... 

Control strategies of a microgrid which includes both synchronous generators and converter-based distribution generation (DG) units must be designed such that effective operation of the microgrid is achieved. The main objective of this paper is to develop a high performance control strategy for an islanded medium voltage (MV) microgrid consisting of inverter and non-inverter interfaced DG units. A new control method for the synchronous generator in an islanded microgrid is proposed based on a virtual droop scheme. The proposed strategy can effectively manage the real and reactive powers of the microgrid among the inverter and non-inverter based DG units. The steady state and dynamic... 

Removal of Metronidazole (MNZ) and Oxytetracycline (OTC) from wastewater by the prepared (C, N codoped)-TiO2/g-C3N4 (Graphitic carbon nitride) was examined. L-Arginine (C, N codoped)-TiO2 and L-Arginine (C, N codoped)-TiO2/g-C3N4 photocatalysts were successfully synthesized through the sol-gel method, and optimal ratio of L-arginine:TiO2, as well as L-arginine/TiO2:g-C3N4, was determined by a kinetic study of photodegradation process. The maximum photocatalytic removal rate (0.062 min−1 for MNZ removal) was observed using 1% L-Arginine-TiO2/g-C3N4 (1:1) under visible light illumination, 2.2 and 12.4 times greater than those of 1% L-Arginine-TiO2 and pure TiO2, respectively. L-Arginine... 

In this article we prove the stationarity of the solution of the H-valued integral equation, where H is a real separable Hilbert space. In this equation, U(t) is a semigroup generated by a strictly negative definite, self-adjoint unbounded operator A, such that A-1 is compact and f is of monotone type and is bounded by a polynomial and V (t) is a cadlag adapted stationary process  

Spatially structured neural networks driven by jump diffusion noise with monotone coefficients, fully path dependent delay and with a disorder parameter are considered. Well-posedness for the associated McKean-Vlasov equation and a corresponding propagation of chaos result in the infinite population limit are proven. Our existence result for the McKean-Vlasov equation is based on the Euler approximation that is applied to this type of equation for the first time. © 2020 Institute of Mathematical Statistics  

Effective and efficient methods in computational mechanics have been of interest for the designers and engineers in the last decade. A 3D super elements is developed and implemented for the free vibration analysis of the composite plates. These new elements have been constructed by a 2D super elements in the plane direction and p-version finite element in the thickness direction. Results of 2D super elements are comparable to SHELL 63 and results of 3D super elements with cubic polynomial are comparable to SHELL 93. In the thin plates, 2D super element (or SHELL 63) and 3D super elements (or SHELL 93) have same results, but in the thick plates results change drastically. Natural frequencies... 

L-Proline (2%)-TiO2/BiOBr (30%) nanocomposite was synthesized to obtain high photocatalytic performance in the visible light region and infrared radiation(IR) for methylene blue (MB) and congo red (CR) removal from the contaminated wastewater. L-Proline (2%)-TiO2/BiOBr (30%) photocatalyst with strong absorption near IR wavelength and high charge separation ability was fabricated for the first time. X-ray diffraction (XRD), Fourier transform infrared (FTIR), field-emission scanning electron microscope (FESEM)/Energy Dispersive X-ray (EDX), UV–Vis diffuse reflectance spectrum (DRS), photoluminescence (PL) and Brunauer-Emmett-Teller (BET) characterization techniques show that the visible driven... 

Background. Temporary artery clipping facilitates safe cerebral aneurysm management, besides a risk for cerebral ischemia. We developed an artificial neural network (ANN) to predict the safe clipping time of temporary artery occlusion (TAO) during intracranial aneurysm surgery. Method. We devised a three-layer model to predict the safe clipping time for TAO. We considered age, the diameter of the right and left middle cerebral arteries (MCAs), the diameter of the right and left A1 segment of anterior cerebral arteries (ACAs), the diameter of the anterior communicating artery, mean velocity of flow at the right and left MCAs, and the mean velocity of flow at the right and left ACAs, as well... 

ZnS nanoparticles were synthesized through a one-step precipitation process. Effect of time and temperature on the formation reaction was investigated. The synthesized samples were characterized by X-ray diffraction (XRD), ultraviolet (UV) visible absorption and photoluminescence (PL) spectrophotometry. Based on XRD and UV-Vis data, the particles produced at 70 °C had a mean particle size of about 5 nm. Increasing time and temperature of the synthesis reaction resulted in photoluminescence intensification. PL spectroscopy helped understanding the adsorption kinetics of oxygen on ZnS nanoparticles during the precipitation synthesis process. Fabrication of ZnS structures with appropriate... 

We propose a hybrid graphene molybdenum disulphide-based photoconductive antenna to overcome the restrictions of metallic photoconductive antennas and graphene-based photoconductive antennas, simultaneously. The structure is composed of a hybrid graphene-MoS2 strip as the antenna deposited on a low-temperature gallium arsenide substrate. A full-wave electromagnetic solver, namely, high frequency structural simulator (HFSS) is used to analyze the whole structure. It is shown that the proposed photoconductive antenna provides us with not only high input impedance and reconfigurability but also high values of matching efficiency and radiation efficiency. The impact of increasing MoS2 layers on... 

In this paper, we report on a novel resonant THz sensor for label-free analysis. The structure consists of a silicon nitride dielectric ring resonator vertically coupled to a thin layer of graphene strip ring resonator on top. The cladding is assumed to be porous alumina on the top of the graphene strip, which enhances the interaction of the surface plasmon wave and the target molecules. Finite difference time domain analysis is used to systematically design the structure and to investigate the performance of the sensor. Our simulations show that the proposed structure has larger refractive index sensitivity and lower intrinsic quality factor with respect to the similar optical structure. It... 

Here, the existence and measurability of solutions for stochastic differential equations driven by fractional Brownian noise with Hurst parameter greater than 1 2 is proved. Our method is based on approximating the main equation by delayed equations as in Peano's method in ODEs. This method makes the proofs easier and needs weaker assumptions for the existence part, compared with the previous works as in [25]. In addition the constructive nature of the proofs helps to develop some numerical methods for solving such SDEs. © 2009 Iranian Mathematical Society  

In this contribution a new approach to perform spatial integration is presented using a dielectric slab. Our approach is indeed based on the fact that the transmission coefficient of a simple dielectric slab at its mode excitation angle matches the Fourier-Green's function of first-order integration. Inspired by the mentioned dielectric-based integrator, we further demonstrate its graphene-based counterpart. The latter is not only reconfigurable but also highly miniaturized in contrast to the previously reported designs [Opt. Commun. 338, 457 (2015)]. Such integrators have the potential to be used in ultrafast analog computation and signal processing. © 2017 Optical Society of America