Sharif Digital Repository

The high dependence of the atmospheric carbon dioxide emissions on fossil fuels has led it to increment. Process design along with the economic aspects, improves the technology diffusion of the carbon capturing. In the pressure swing adsorption as a promising carbon capturing technology, increasing the pressure leads to more adsorbed amount of carbon dioxide and energy consumption of compressor, which is a source for carbon dioxide emission. Experimental data shows that for pressures between 3 to 5 bar, the avoided CO2 is in maximum rate. The economic analysis reveals that the pressure of 3 bar is appropriate. Also, the utilization of CO2 in the aerogel production, as a nano-based thermal... 

The high dependence of the atmospheric carbon dioxide emissions on fossil fuels has led it to increment. Process design along with the economic aspects, improves the technology diffusion of the carbon capturing. In the pressure swing adsorption as a promising carbon capturing technology, increasing the pressure leads to more adsorbed amount of carbon dioxide and energy consumption of compressor, which is a source for carbon dioxide emission. Experimental data shows that for pressures between 3 to 5bar, the avoided CO2 is in maximum rate. The economic analysis reveals that the pressure of 3bar is appropriate. Also, the utilization of CO2 in the aerogel production, as a nano-based thermal... 

We present a new approach for depth detection of hidden defects based on the analysis of the frequency spectrum of the output waveform in a nondestructive testing (NDT) system. In our eddy current Superconducting quantum interference device (SQUID) based NDT system, we apply multiple frequencies to its single excitation coil in a magnetically unshielded environment. The excitation coil is a planar D-shaped printed circuit board coil, and a high-Tc gradiometer YBCO rf-SQUID is used as the electromagnetic sensor in this system. An automated two-dimensional nonmagnetic scanning robot is used to test samples with intentional defects at different depths. In this approach, a diagram labeled 'FFT... 

We present a new approach for non-destructive evaluation (NDE) in homogeneous and isotropic metallic objects which contain defects at unknown depths based on single scan and multi frequency excitation. As known, there is an optimum frequency for each depth of defect. Finding the depth of an unknown defect requires us to find the optimal frequency. In conventional single frequency methods, the optimal frequency is obtained by applying a wide range of frequencies to the system separately and comparing the corresponding results in a time-consuming process. Conventional multi frequency inspections were introduced to obtain more information about test specimens. There are two ways to apply... 

Growing needs for energy and the essential role of fossil fuels in energy market require attempts such as carbon dioxide (CO2) sequestration in saline aquifers to stabilize and mitigate atmospheric carbon concentrations. The possibility of co-injection of impurities along with CO2 allows for the direct disposal of flue gas and hence a significant reduction in the cost of CO2 sequestration projects by eliminating the separation process. In this study, the results of series of novel experiments in a high-pressure visual porous cell are reported, which allow for visually and quantitatively examining the dynamics of convective dissolution in brine-saturated porous media in the presence of an... 

Small Permanent Magnet Synchronous Generators (PMSGs) are widely used in small rooftop wind turbines. In order to inject the electric power generated by the PMSG, into the grid, a back-to-back AC/DC/AC converter is required. In this paper, a low cost with high efficiency converter is proposed for the rectifier stage to obtain the maximum power per ampere of PMSG. This structure based on Discontinuous Conduction Mode Single-Ended Primary Inductor Converter (DCM SEPIC) with a single power electronic switch, proposes a converter which is cost-effective and suitable for the small wind turbine used in residential applications. Furthermore, other advantages of the proposed converter include... 

We present an ontology based indexing method for unstructured P2P networks. We maintain limited size indexes at each node to identify number of documents accessible on each concept without loosing any indexing information. Out method supports complex queries, combined of conjunction and disjunction phrases. We simulate our search algorithm on an unstructured P2P network and show that our method significantly reduces the network traffic. © 2008 Springer-Verlag  

Small Permanent Magnet Synchronous Generators (PMSGs) are widely used in small rooftop wind turbines. In order to inject the electric power generated by the PMSG, into the grid, a back-to-back AC/DC/AC converter is required. In this paper, a low cost with high efficiency converter is proposed for the rectifier stage to obtain the maximum power per ampere of PMSG. This structure based on Discontinuous Conduction Mode Single-Ended Primary Inductor Converter (DCM SEPIC) with a single power electronic switch, proposes a converter which is cost-effective and suitable for the small wind turbine used in residential applications. Furthermore, other advantages of the proposed converter include... 

Direct-drive permanent magnet synchronous generators enjoy numerous advantages including improved reliability, low maintenance, long life, and developed performance characteristics. In recent years, many researchers have worked on these generators to enhance their performance, especially for the wind turbine application. The focus of this paper is on the development of a step-by-step method for the design of a permanent magnet synchronous generator. Then, the winding function method is used to model the generator and calculate its output characteristics analytically. The analytical results of the designed generator are validated using Finite Element Analysis (FEA) and it is demonstrated that... 

In millimeter-wave (MMW) imaging, the objects of interest are oftentimes modeled as 2-D binary (black and white) shapes with white pixels representing the reflecting interior of the object. However, due to the propagation of the scattered waves, the continuous-domain binary images are convolved with a so-called point-spread function (PSF) before being digitized by means of sampling. As the 2-D PSF is both nonseparable and nonvanishing in the case of MMW imaging, exact recovery is quite complicated. In this communication, we propose a deep-learning approach for image reconstruction. We should highlight that the wave scatterings are suitably represented with complex-valued quantities, while... 

Aim: The aim of this study is to look for the proper methods that would be a major step towards untreated CD diagnosis and seek the metabolic biomarkers causes of CD and compare them to control group. Background: Celiac disease (CD) is a common autoimmune disorder that is not easily diagnosed using the clinical tests. Patients and methods: Thirty cases and 30 controls were entered into this study. Metabolic profiling was obtained using proton nuclear magnetic resonance spectroscopy (1HNMR) to seek metabolites that are helpful for the detection of CD. Classification of CD and healthy subject was done using random forest (RF). Results: The obtained classification model showed an 89% correct... 

The electrocatalytic oxidation of methanol was studied over Ni, Co and Cu binary or ternary alloys on graphite electrodes in a NaOH solution (0.1 mol/L). The catalysts were prepared by cycling the graphite electrode in solutions containing Ni, Cu and Co ions at cathodic potentials. The synergistic effects and catalytic activity of the modified electrodes were investigated by cyclic voltammetry (CV), chronoamperometry (CA) and electrochemical impedance spectroscopy (EIS). It was found that, in the presence of methanol, the modified Ni-based ternary alloy electrode (G/NiCuCo) exhibited a significantly higher response for methanol oxidation compared to the other samples. The anodic peak... 

The aim of this study is to evaluate the sustainability of two actual wastewater treatment plants using the eco-efficiency index based on emergy and life cycle analysis. The life cycle analysis is used for environmental investigation to estimate the eco-efficiency index. Moreover, the emergy theory indicating the input and output flows of the ecosystem are applied to assess the sustainability considering ecosystem services. Two treatment plants are studied in the city of Mashhad in Iran. The potential for sustainability improvement of plants is analyzed in some scenarios including the production of agricultural compost from sludge, 10% reduction of energy consumption, and 10% reduction of... 

Penetration of distributed generation (DG) in distribution networks is rapidly increasing. DGs' application enhances system's reliability and power quality. However, along their benefits, there are some issues. One of the most important issues of DGs' application is the islanding. This paper presents a novel passive islanding detection scheme for synchronous DG based. In the proposed scheme, rate of change of exciter voltage over rate of change of reactive power at the DG-side (dE/dQDG) is taken into account. In reality, the voltage and reactive power of load depend on the exciter of the synchronous generator. Therefore, due to lack of inertia, response of these parameters to small changes... 

The aim of this study is to quantify the water-energy-emissions nexus in wastewater treatment plants (WWTPs). At first, energy auditing is done for two real WWTPs to find out the energy consumption of different plant stages and the energy-saving potentials. The power plant and carbon capture units are taken into account to assess the energy-emission nexus based on emergy flows. Then, the emergy analysis is applied to evaluate the environmental, economic and technical aspects. An emergy performance index (EmIGHG) is presented by the means of emergy flow diagram of the WWTP beside a power plant (considering the electricity production emergy cost) and carbon capture unit (considering the CO2... 

Recently, cloud computing infrastructure (CCI) models have received much attention for their exceptional scalability, dependability, Data Information Sharing (DIS), and low cost rate. There are many hardware and software elements that are accessed over the internet by cloud data centers. Modern data centers utilize Virtualization Techniques (VT) to offer a dispersed CI that employs Virtual Machines (VM) based on Physical Hosts (PH). With the increasing number of centers, optimizing energy consumption has become vital to saving costs due to DCC's high energy consumption. In our CPS algorithm, we combine the Cuckoo algorithm and the particle swarm optimization (PSO). It is determined which... 

This paper studies unamped oscillations of fractional-order Duffing system. Stability theorems for fractional order systems are used to determine the characteristic polynomial of the system in order to find the parametric ranges for undamped oscillations in this system. We also derive relations for estimating the frequency and the amplitude of the oscillations in this system using a describing function method. Finally numerical simulation results are provided to justify the analysis  

This paper deals with the existence and the characteristics of the limit cycles in the fractional-order Arneodo system. The analysis is done using the describing function method. Our focus is on a special case where two limit cycles exist. The parametric range for the case of interest is derived, and the frequency and the amplitude of the oscillation are predicted. Numerical simulation results are presented to further demonstrate the reliability of the analysis  

This paper studies undamped oscillations of fractional-order Duffing system. Stability theorems for fractional order systems are used to determine the characteristic polynomial of the system in order to find the parametric ranges for undamped oscillations in this system. We also derive relations for estimating the frequency and the amplitude of the oscillations in this system using a describing function method. Finally numerical simulation results are provided to justify the analysis  

As steel plate shear walls are typically used in the building central cores around the elevators and stairs, introduction of an opening as door seems to be inevitable in steel plate shear wall spans. Due to the weakening of the steel plate shear walls’ performance caused by this particular type of opening, the use of stiffeners around the opening is necessary. Nevertheless, introduction of stiffeners around all sides of the opening, which does continue to boundary elements, is very expensive and inefficient. Therefore, the study on the effect of different arrangements of stiffeners on the behavior of steel plate shear walls is significant. In this research, a number of steel plate shear...