Qom University Of Technology
Recent publications
This paper proposes a tri-stage energy management framework to determine the best operation planning of an energy hub system (EHS) considering economic aspects, reliability, and thermal and electrical generation flexibility. The first stage of the suggested framework focuses on the economic operation planning of EHS. The operator of EHS handles the uncertainty of market prices and renewable resources to provide the primary scheduling from the economic point of view. In the second stage, the primary scheduling of EHS has been modified to enhance the thermal and electrical flexibility in order to cover the existing uncertainties. Increasing system flexibility is achieved by increasing system reservation, but maximizing flexibility should not lead to a lack of energy for consumers. Therefore, the third stage evaluates the operation scheduling of EHS from the electrical and thermal energy not supplied perspective. Also, the plug-in electric vehicle, electric storage, thermal storage, ice storage, electrical and thermal demand response programs are integrated into EHS to enhance the system flexibility. The proposed model is tested on a standard case stud and the simulation result shows that the proposed tri-stage framework improves the generation flexibility, and thermal load shedding by 46.74 and 58.85 %, respectively.
The aim of present work is to analyze a U-type of evacuated tube solar collector in which phase change material (PCM) is employed to store surplus solar energy in daytime and reuse it at nighttime when the solar irradiation vanishes. Both charging and discharging processes are considered and modeled. Two critical points should be considered in designing the proposed collector; the stable requirement outlet temperature of the domestic solar collector during daytime (about 40°C) and assurance of a complete melting/solidification process to reach the maximum energy storage and release. Since the absorbed energy from solar radiation by heat transfer fluid and PCM in both day and nighttime strongly depends on the U-type tube's diameter, three values of which (namely, 6, 8, and 10 mm) are selected to attain the best case. The results show that the case with 6 mm diameter yields a 25% and 13.5% improvement in the liquid fraction and fluid outlet temperature, respectively, at 3:00 PM in the charging process, compared to other cases. Also, this case has achieved a 20% delay in the thermal energy release process and has increased the fluid outlet temperature by 24%, compared to other cases, at 9:00 PM in the discharging process.
In the current paper, we try to engineer the refractive index profile in a one-dimensional photonic crystal as a powerful tool to manage the electromagnetic wave transmission properties. For this purpose, we have compared four sinusoidal, rectangular, triangular, and saw-tooth refractive index profile types. In this way, we have used a transfer matrix method accompanied by the discretization of the spatial domain. This method can readily be applied to any arbitrary continuous refractive index profile. Then, we have tried to address the effects of different geometrical and physical parameters, including the photonic crystal length L, dielectric permittivity εd\documentclass[12pt]{minimal} \usepackage{amsmath} \usepackage{wasysym} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{amsbsy} \usepackage{mathrsfs} \usepackage{upgreek} \setlength{\oddsidemargin}{-69pt} \begin{document}$$\varepsilon_{d}$$\end{document}, the number of layers and plasma density np, etc. on the light propagation through the mentioned photonic crystals. Furthermore, we have investigated the effect of the refractive index profile type on the transmission spectra and shown that there is no transmission in frequencies greater than 100 GHz for saw-tooth, sinusoidal, and triangular refractive index. But the behavior of the rectangular refractive index profile is different from that of the other assumed systems.
In this study, the energy charging mechanism is mathematically modeled to determine the impact of design modifications on the thermofluidic behavior of a phase change material (PCM) filled in a triplex tube containment geometry. The surface area of the middle tube, where the PCM is placed, is supported by single or multi-internal frustum tubes in vertical triplex tubes to increase the performance of the heating and cooling of the system. In addition to the ordinary straight triplex tubes, three more scenarios are considered: (1) changing the middle tube to the frustum tube, (2) changing the inner tube to the frustum tube, and (3) changing both the internal and central tubes to the frustum tubes. The impact of adopting the tube designs and gap width were studied. The outcomes reveal that the heat storage rates are increased for all frustum tube systems compared to the straight tube system. According to the results, the case of a gap width of 5 mm is the optimal one among the studied cases in terms of the melting time and the heat storage rate. Employing the frustum tube configuration with a 5-mm gap width would save the melting time by 25.6% and increase the rate of heat storage by 32.8% compared to the base case of straight tubes.
In this research, a novel synthesis of CaO nanoparticles via a green, environmentally, and economical method is developed. Crataegus pontica C.Koch leaves extract was used as a green reducing and stabilizing agent to synthesize the calcium oxide nanoplates ranging from 40 to 65 nm. The synthesized CaO NPs are characterized by scanning electron microscopy (SEM), X-ray powder diffraction (XRD), transmission electron microscopy (TEM), and Fourier transform infrared (FT-IR) spectroscopy. The CaO NPs were evaluated successfully for photocatalytic degradation of methylene blue (MB) dye with 98.99% degradation efficiency under sunlight by a simple technique. The recoverability and reusability of the CaO photocatalyst were considered under the optimized reaction conditions, which are showed high chemical stability after at least five runs. Graphical abstract
Fault detection is one of the most important research topics till today in the field of VSC-HVDC grids protection. In this subject, fast and reliable identification of faults is the most demanding issue, which still requires further study. In this respect, this paper proposes an index for fault detection, which is based on correlation between the powers of DC-link capacitor and the protected line. It is proved by an analytical time-domain transient expression that there is a direct correlation between these two powers under fault conditions. To implement this scheme, the routing of the discharged power of DC-link capacitor into the protected line is the key technique. To do so, the Pearson correlation factor is used in this paper, which efficiently captures the level and direction of the correlation between these two powers. The proposed method benefits from different salient features of very fast fault detection, accurate discrimination of faulted line from healthy lines, covering high-resistance faults, noise immunity, robustness against severe power reversal conditions, robustness against low sampling frequencies, not requiring extra sensor and communication infrastructure, etc. To evaluate the performance of the proposed approach, a complete set of fault scenarios are simulated on a meshed multi-terminal MMC-based VSC-HVDC network.
Aortic aneurysm is one of the most common aortic diseases that can lead to unfortunate consequences. Numerical simulations have an important role in the prediction of the aftereffects of vascular diseases including aneurysm. In this research, numerical simulation of pulsatile blood flow is performed for a 3-dimensional patient-specific model of a thoracic aortic aneurysm (TAA). Since the choice of blood viscosity model may have a significant impact on the simulation results, the effects of four non-Newtonian models of blood viscosity namely Carreau, Casson, Herschel-Bulkley, power low, and the Newtonian model on the wall shear stress (WSS) distribution, shear rate, and oscillatory shear index (OSI) have been analyzed. Simulation results showed that all the non-Newtonian and Newtonian models generally, predict similar patterns for blood flow and shear rate. At high flow rates in the cardiac cycle, the WSS value for all the models are similar to each other except for the power-law model due to the shear thinning behavior. All models predict high values of OSI on the inner wall of the ascending aorta and broad areas of the inner wall of the aneurysm sac. However, the Newtonian model predicts the OSI less than the non-Newtonian models in some areas of the aneurysm sac. Results indicated that the Newtonian model generally can predict the hemodynamic parameters of the blood flow similar to the non-Newtonian but for more precise analysis and to predict the regions prone to rupture and atherosclerosis, choosing a proper non-Newtonian model is recommended.
In this article, a dual circular polarized antenna fed by double quadrature couplers is presented. The proposed structure consists of three parts: dual‐polarization antenna, quadrature couplers, and connection structure. This structure is not sensitive to orientation due to its circular polarization. The antenna gain can be easily increased by cascading orthogonal dipoles. Therefore, this array structure has a fan beam circular polarized radiation pattern. This structure is fabricated on the Rogers 4003C substrate. The simulation and measurement results show that this proposed antenna achieves return loss above 10 dB in the frequency range of 9.8–10.2 GHz.
Fe2TiO5, pseudobrookite, with a high Seebeck coefficient and very low thermal conductivity, shows promising thermoelectric properties. However, due to its low electrical conductivity, the ZT value of Fe2TiO5 is still very low. In this article, we report the effect of the Nb substitute on the crystal structure, electronic, magnetic and thermoelectric properties of Fe2TiO5 by employing first-principle calculations. The calculated electronic structures in GGA + U show that introducing Nb improves the electrical conductivity of the Fe2TiO5 and with the increasing Nb atoms content, the size of the band gap decreases. Our spin-polarized calculations reveal that Fe2−xNbxTiO5 components with X = 0.125 and 0.375 have an absolute magnetization, while Fe2TiO5 shows anti-ferromagnetism behavior. As the amount of Nb in the Fe2TiO5 composition increases, the Seebeck coefficient increases. Also, in all samples, with increasing temperature, the Seebeck coefficient decreases. These results show that thermoelectric properties are improved by adding Nb to the compounds.
Fingerprint has been widely used in biometric applications. Numerous established researches on image enhancement techniques have been done to improve the quality of fingerprint images. However, the production of low-quality images due to the presence of scars remains a challenge in biometrics. The scars damage the fingerprint minutiae information due to broken ridges and they reduce the accuracy of identification. This research developed an image enhancement approach to improve the quality of scarred fingerprint images to generate accurate minutiae extraction. To achieve the aim, the scarred image was improved by removing noise using a new filter, Median Sigmoid (MS), and the corrected ridges were reconstructed using ridges structure enhancement algorithm. This was done to enhance the broken ridges structure. MS filter is a combination of median filter and modified sigmoid function that improves the image contrast and simultaneously removes noise in the fingerprint image. Following that, the filtered image was used in the ridges structure enhancement process. To identify true minutiae, the broken ridges structure in the filtered image needed to be accurately verified. In the ridges structure reconstruction process, an algorithm was enhanced to identify the best value of Sigma parameter (σ) used in the Gaussian Low-pass filter to generate a better orientation image. The image is important to reconstruct the corrupted fingerprint ridges structure. The evaluation for the proposed approach used the National Institute of Standards and Technology Special Database 14, and the results showed a 37% improvement of the quality index in comparison to approaches found in related research. The findings of the evaluation showed that the proposed enhancement approach produced a better minutiae extraction result and this is very significant in the field of fingerprint image enhancement.
Microbial fuel cells (MFCs) produce clean energy and treat wastewater simultaneously. In this study, real wastewater from municipal and dairy sources were used for power generation and wastewater treatment in MFC. The same media and anaerobic conditions were used for keeping them in the 100-ml beaker before being applied to the MFCs. Performance of the MFC is affected by operating conditions, so they must be optimized. Aeration (60–200 ml/min) and yeast extract (2–10 g/l) are important operating parameters used to achieve the best response for power density and COD removal. These parameters are optimized using central composite design (CCD) coupled with response surface methodology (RSM). Based on experimental results, power density and COD removal models are well supported by experimental data. For both wastewater types, the optimal amount of aeration and yeast extract is about 125 ml/min and 2 g/l, respectively. The optimal operating conditions resulted in a power density of 481 mW/m² for municipal wastewater microorganisms in 1180 mV, and 410 mW/m² for dairy wastewater in 1070 mV.The MFC which works with municipal wastewater microorganisms has a lower internal resistance compared to dairy wastewater. MFC reduced COD in municipal and dairy wastewater by 84% and 70%, respectively, and their coulombic efficiencies (CE) were 37% and 17%, respectively. The scanning electron microscopy (SEM) results showed that microorganism attachment to the electrode in municipal wastewater was significantly higher than in dairy wastewater. Further, the CE found that more organic matter could be degraded into electricity in municipal wastewater than in dairy wastewater. According to this study, MFC works better with higher and more complex wastewater due to the various bacteria embedded on the electrodes and a higher wastewater content.
This paper considers the output tracking problem of non‐minimum phase non‐linear systems using the inverse dynamics control which is impossible in conventional methods due to unstable zero dynamics. The proposed method is based on the output redefinition approach defined as a parametric function. The tracking error is decomposed into two terms. The first one named redefined output tracking error is the difference between the redefined output and the reference signal, and the second one is the distance between the redefined output and the system output. For the first term, due to minimum phase property of the system with the redefined output, an inverse dynamics control is used to guarantee the convergence of the redefined output tracking error to zero. To minimize the second term, the parameters of the redefined output are set by solving an optimization problem whose constraints include minimum phase conditions. To solve the optimization problem which satisfies all constraints, the barrier function method as an interior point method is adopted. The optimization parameters are set using steepest descent algorithm. Due to on‐line updating the redefined output parameters, the related zero dynamics is time varying. Therefore, sufficient conditions for exponential stability of the resulting time‐varying zero dynamics are obtained.
To be competitive, organizations must also be innovative, making organizational creativity a crucial capability. Accordingly, the past decade has seen an increasing attention among scholars to fields such as innovation, organizational performance, and creativity. Nevertheless, studies in organizational creativity, i.e., the management of creativity at an organizational level, are still fragmented and have not converged into a single comprehensive conceptual model. The purpose of this paper is to scrutinize the literature on organizational creativity in order to map the different perspectives on the subject and provide direction for future research. The paper thoroughly explores the literature through bibliographic research on papers published between 1980 and 2020. The literature is mapped, categorized, and analyzed to identify the different models of organizational creativity, i.e., concepts, definitions, and theories. The paper identifies seven models and shows that field could converge by connecting two tracks of the literature: the track of the dynamic componential model with the track of the personal and contextual factors. Furthermore, the paper uses this insight to propose practical guidelines for managing creativity by mapping contextual factors at the individual, team, and organizational levels that can be used with the dynamic componential model.
In this work, we present the new photodetector based on snowflake quantum rings (QRs) structure utilizing a two-dimensional tight-binding model. Optical absorption has calculated and compared with different usual geometries of rectangular, triangular and circular QRs. There are narrow dominant peaks in the absorption spectrum with a low FHWM of 15 meV in the range of 50 meV in the far-infrared (FIR) regime to 300 meV in the mid-infrared (FIR) regime. The two-dimensional confining potential for Koch shaped quantum ring had been described in previous work was inserted in the tight-binding method and probability density of nine lowest electron energy states and absorption have calculated for the first time. Using these results, some properties of QRs were predicted and their validity was examined and displayed further. For a Koch shape quantum ring, there is fine displacement about 3 meV in absorption peak in long-wavelength infrared regime with changing iteration number that can be used for fine-tuning of the absorption spectrum. Also, a circular ring with minimal energy states has absorption peaks with an average full width at half maximum of 12.5 meV that can be tuned with the resolution of 13 meV in the FIR regime. These results are more applicable for an experimentalist to design a new photodetector with a narrower sharp peak for applications like night-vision, a thermal detector, and total IR absorbers.
This paper proposes an adversary-resilient communication-efficient distributed estimation algorithm for time-varying networks. It is a generalization of the doubly compressed diffusion least mean square algorithm that is not adversary-resilient. The major drawback in existing adversary detectors in the literature is that they suggested the detection criterion heuristically. In this paper, an adversary detector is suggested theoretically based on a Bayesian hypothesis test (BHT). It is proved that the test statistics of the detectors is a distance metric compared to a threshold similarly to related papers in the literature. Hence, we prove the validity of the detection criterion based on BHT. The other difficulty encountered in existing works is the determination of thresholds. In this paper, the optimum thresholds are derived in closed form. Since the optimum thresholds need the values of unknown parameters, it is not feasible to derive them. Hence, suboptimal procedures for determining the thresholds are provided. Moreover, the convergence of the mean of the algorithm is investigated analytically. In addition, the Cramer–Rao bound of the problem of distributed estimation based on all node observations in the presence of adversaries is calculated. The simulation results show the effectiveness of the proposed algorithms and demonstrate that the proposed algorithms reach the performance of the algorithm when the adversaries are ideally known in advance, with some delay.
To prepare a fully organic polylactic acid (PLA)‐based bio‐nanocomposite, cellulose nanocrystals (CNCs) were grafted by PLA through ring‐opening polymerization (ROP) of L‐lactide monomers onto CNCs. The grafting process was evaluated by 1HNMR and FTIR spectroscopic methods. The effect of surface‐modified CNCs (M‐CNCs) was investigated on thermal, mechanical, rheological, and dynamic mechanical thermal properties of PLA. The M‐CNCs were successfully dispersed in the PLA matrix. Isothermal and non‐isothermal DSC studies revealed that M‐CNCs caused an intensive increase in crystallization kinetics and therefore nucleation density and crystallization extent. DSC, XRD, and DMTA analyses indicated the formation of different crystal structures [α, α', β] in PLA after addition of M‐CNCs. Rheological analysis was carried out for microstructural investigation of the nanocomposites. Interestingly, after the addition of M‐CNCs not only the tensile strength and modulus of the samples increased but also the toughness of PLA was considerably improved. Isothermal and non‐isothermal DSC studies revealed that modified cellulose nanocrystals (M‐CNCs) caused an intensive increase in crystallization kinetics and therefore nucleation density and crystallization extent of PLA. Interestingly, after the addition of M‐CNCs not only did the tensile strength and modulus of the samples increase but also the toughness of PLA was considerably improved.
Introduction: The present study aimed to investigate the change of air pollutants in 2020 in Qom compared to the same period in 2019 in five scenarios. Materials and Methods: The hourly air quality data was obtained from air quality monitoring stations of Qom Environmental Protection Organization (EPO). The meteorological parameters were obtained from Iranian Meteorological Organization website. The data were analyzed using Excel, SPSS, and WRPLOT view. Results: In the first month of the COVID-19 crisis, NO2, SO2, and CO decreased by 26.4, 39, and 0.2 µg/m3 compared to same period in 2019, respectively; however, PM2.5 and O3 increased by 7.1 and 2.3 µg/m3, respectively. In Iranian Nowruz holidays, an increase of 2.9 µg/m3 in O3 mean concentration and a decrease of 8.1, 23.8, 22.8, and 0.2 µg/m3 in mean concentration of PM10, NO2, SO2, and CO were experienced. The prevailing wind direction during the 2020 in each scenario was from the west of Qom city. Conclusion: Gaseous pollutants decreased during the crisis, but particulate pollutants increased slightly compared to the same period in 2019. The lockdown may have had the most impact in decreasing pollutants. A slight increase in wind speed from the west could be a factor in increasing particles. This crisis provided an opportunity to assess the role of policies, such as traffic reduction plans or discarding worn-out cars or urban management to improve air quality.
Seismic stability of geotechnical structures is an essential issue in earthquake geotechnical engineering. The pseudostatic method is the most common method for seismic stability analysis of geotechnical structures. The pseudodynamic method was developed, considering the phase differences and time effects; however, it does not satisfy the zero stress boundary conditions at the surface. A modified pseudodynamic method was proposed according to the zero stress boundary conditions for harmonic base motion. In the formulation of the modified pseudodynamic method, the ground motion of an earthquake with its frequency content is not considered. Also, the imaginary part of the response related to the damping effect is removed, making it more difficult to develop than expected. The pseudostatic and pseudodynamic methods are overestimated because the failure wedge is determined similar to the static method. This study aims to propose a new pseudodynamic method for seismic analysis of geotechnical structures considering the earthquake ground motion and both the real and the imaginary parts of the response. New transfer functions are introduced to obtain inertial forces and seismic active pressure based on the input motion. Furthermore, according to the experimental observations and momentum theory, a new method is proposed to determine the critical failure surface accurately. A comparison with a few experimental and analytical results in the literature is also presented. The results of the proposed method are in good agreement with the experimental and analytical results. Finally, an example is provided to illustrate the application of the proposed method. The effects of shear wave velocity and wall height on the seismic active pressure during an earthquake are investigated.
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173 members
Majid Mohammadi
  • Energy Engineering
Seyed Mohammad Dehghan
  • Faculty of Electrical and Computer Engineering
S. M. A. Aleomraninejad
  • Department of Mathematics
Roozbeh Rajabi
  • Electrical and Computer Engineering Department
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Jalal Rezaeenour
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