A5067912538- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Antenna Design and Optimization
- Power System Reliability and Maintenance
- Galaxies: Formation, Evolution, Phenomena
- Optimal Power Flow Distribution
- Soil Moisture and Remote Sensing
- Superconducting and THz Device Technology
- Scientific Research and Discoveries
- Space Satellite Systems and Control
- Islanding Detection in Power Systems
- Radio Wave Propagation Studies
- Microgrid Control and Optimization
- Power Systems and Renewable Energy
- Plant Surface Properties and Treatments
- Spacecraft Dynamics and Control
- Electric Power System Optimization
- Advanced Measurement and Metrology Techniques
- Power Systems Fault Detection
- Islamic Finance and Banking Studies
- Inertial Sensor and Navigation
- Combustion and flame dynamics
- Electrical Fault Detection and Protection
- Fluid Dynamics and Heat Transfer
- Advancements in Battery Materials
University of Waterloo
2024
Semnan University
2020
Sharif University of Technology
2007-2019
Netherlands Institute for Radio Astronomy
2013-2016
Astronomy and Space
2013-2015
AstroTec Holding (Netherlands)
2015
University of Groningen
2011-2014
Aalto University
2012
The aim of the new generation radio synthesis arrays such as LOw Frequency ARray (LOFAR) and Square Kilometre Array (SKA) is to achieve much higher sensitivity, resolution frequency coverage than what available now, especially at low frequencies. To accomplish this goal, accuracy calibration techniques used considerable importance. Moreover, since these telescopes produce huge amounts data, speed convergence a major bottleneck. errors in are due system noise (sky instrumental) well...
The aim of the LOFAR Epoch Reionization (EoR) project is to detect spectral fluctuations redshifted HI 21cm signal. This signal weaker by several orders magnitude than astrophysical foreground signals and hence, in order achieve this, very long integrations, accurate calibration for stations ionosphere reliable removal are essential. One prospective observing windows EoR will be centered at North Celestial Pole (NCP). We present results from observations NCP window using highband antenna...
This study aims to characterize linear polarization structures in LOFAR observations of the interstellar medium (ISM) 3C196 field, one primary fields LOFAR-Epoch Reionization key science project. We have used high band antennas (HBA) image this region and Rotation Measure (RM) synthesis unravel distribution polarized Faraday depth. The brightness temperature detected Galactic emission is $5-15~{\rm K}$ intensity covers range from -3 +8 ${\rm rad~m^{-2}}$ most interesting morphological...
One of the most promising ways to study epoch reionization (EoR) is through radio observations redshifted 21-cm line emission from neutral hydrogen. These are complicated by fact that mapping redshifts line-of-sight positions distorted peculiar velocities gas. Such distortions can be a source error if they not properly understood, but also encode information about cosmology and astrophysics. We effects redshift space on power spectrum radiation EoR using large scale $N$-body radiative...
This study aims to characterise the polarized foreground emission in ELAIS-N1 field and address its possible implications for extraction of cosmological 21-cm signal from Low-Frequency Array - Epoch Reionization (LOFAR-EoR) data. We use high band antennas LOFAR image this region RM-synthesis unravel structures at Galactic latitudes. The brightness temperature detected is on average 4 K intensity covers range -10 +13rad m^-2 Faraday depth. total polarization angle show a wide morphological...
LOFAR is the LOw Frequency Radio interferometer ARray located at mid-latitude ($52^{\circ} 53'N$). Here, we present results on ionospheric structures derived from 29 nighttime observations during winters of 2012/2013 and 2013/2014. We show that able to determine differential TEC values with an accuracy better than 1 mTECU over distances ranging between 100 km. For all power law behavior phase structure function confirmed a long range baseline lengths, $1$ $80$ km, slope in general larger...
Aims. This paper discusses the spectral occupancy for performing radio astronomy with Low-Frequency Array (LOFAR), a focus on imaging observations.
The first generation of redshifted 21 cm detection experiments, carried out with arrays like LOFAR, MWA and GMRT, will have a very low signal-to-noise ratio per resolution element (\sim 0.2). In addition, whereas the variance cosmological signal decreases on scales larger than typical size ionization bubbles, formidable galactic foregrounds increases, making it hard to disentangle two such large scales. poor sensitivity small one hand, effect other make direct imaging Epoch Reionization...
A major stage of radio interferometric data processing is calibration or the estimation systematic errors in and correction for such errors. stochastic error (noise) model assumed, most cases, this underlying assumed to be Gaussian. However, outliers due interference sky would have adverse effects on based a Gaussian noise model. Most shortcomings as loss flux coherence, appearance spurious sources, could attributed deviations In paper, we propose improve robustness by using Student's t...
Automation can greatly enhance distribution-network reliability by speeding up service restoration and thus significantly reduce customer-outage time. The paper presents an approach to assess quantitatively the adequacy of a particular automated distribution scheme designated as 'low interruption system' (LIS). Owing use high-speed communication system line sensors, this drastically number interruptions, time also area affected fault. This provides simple cost-effective way automate systems...
The issue of unity and convergence is one the key objectives Islamic law, a mandate reason Sharia, significant concern for reformers prominent religious scholars throughout history. A cursory review Qur'anic verses narrations reveals that mission scholars—as agents propagators Islam—is universal, intended guidance all humanity without being constrained by geographical or political borders. purpose this study to examine question: How role in achieving assessed, what strategies have been...
Loop restoration scheme (LRS) is a special feeder automation (FA) scheme, which used by utilities to improve distribution system reliability. The LRS controlled and managed its automatic control (ACS). impacts on reliability indices of implementing mainly depend the type ACS. Two common types ACS are presented in this study. Successful operation dependent protection functions switching devices LRS. Different failure modes these can therefore affect procedure fault detecting, isolating...
The new generation of radio synthesis arrays, such as Low Frequency Array and Square Kilometre Array, have been designed to surpass existing arrays in terms sensitivity, angular resolution frequency coverage. This evolution has led the development advanced calibration techniques that ensure delivery accurate results at lowest possible computational cost. However, performance is still limited by compact, bright sources sky, used calibrators. It important a enough source well distinguished...
We discuss the feasibility of detection 21cm forest in diffuse IGM with radio telescope LOFAR. The optical depth to line has been derived using simulations reionization which include detailed radiative transfer ionizing photons. find that spectra from models similar total comoving hydrogen emissivity but different frequency distribution look remarkably similar. Thus, unless histories are very each other (e.g. a predominance UV vs. x-ray heating) we do not expect distinguish them by means...
Using a combination of N-body simulations, semi-analytic models and radiative transfer calculations, we have estimated the theoretical cross power spectrum between galaxies 21cm emission from neutral hydrogen during epoch reionization. In accordance with previous studies, find that is initially correlated halos on large scales (> 30 Mpc), anti-correlated intermediate (~ 5 uncorrelated small (< 3 Mpc) scales. This picture quickly changes as reionization proceeds two fields become The...
We present radio observations of the Moon between $35$ and $80$ MHz to demonstrate a novel technique interferometrically measuring large-scale diffuse emission extending far beyond primary beam (global signal) for first time. In particular, we show that (i) appears as negative-flux source at frequencies $35<\nu<80$ since it is `colder' than Galactic background occults, (ii) using (negative) flux lunar disc, can reconstruct spectrum with thermal reference, (iii) reflected RFI (radio-frequency...
The rapidly growing number of objects encircling our planet is an increasing concern. Collisions between these have already occurred and pose a potential threat in the future, resulting creation countless debris fragments. In particular, Low Earth Orbit (LEO) region densely populated highly contested. This underscores critical importance space surveillance this area. Moreover, utilization Medium (MEO) Geosynchronous (GEO) also on rise. To ensure safety functionality operational satellites,...
We investigate the feasibility of detecting 21cm absorption features in afterglow spectra high redshift long Gamma Ray Bursts (GRBs). This is done employing simulations cosmic reionization, together with instrumental characteristics LOw Frequency ARray (LOFAR). find that could be marginally (with a S/N larger than few) detected by LOFAR at z>7 if GRB originated from PopIII stars, while detection would easier noise were reduced one order magnitude, i.e. similar to what expected for first...
Recently, with the development of electric vehicles (EVs), in order to compensate for undesirable effects charging stations on grid characteristics, paying attention local generators based renewable energy has increased and caused develop peripheral systems. In this paper, a high step-up multistage structure consisting several integrated boost flyback converter (IBFC) been proposed. combination these stages, subconverters are interleaved charge battery bank series supply variable loads. The...
The business activities of the majority industrial and commercial customers are dependent on some critical equipments that susceptible to voltage sag events. This paper aims propose a novel approach estimate financial impacts events customer operations. proposed technique is based event tree method. Using this approach, it possible consider operational failure various sensitive equipments, involved in operations, losses expected from A quantitative case study conducted illustrate...
The main objective of this work is to accelerate the maximum likelihood (ML) estimation procedure in radio interferometric calibration. We introduce ordered-subsets–least-squares (OS–LS) and ordered-subsets–space alternating generalized expectation (OS–SAGE) calibration methods, as a combination OS method with LS SAGE maximization techniques, respectively. algorithm speeds up ML achieves nearly same level accuracy solutions one obtained by non-OS methods. apply OS–LS OS–SAGE methods...
Planning of distribution networks is usually accomplished using a cost-based conventional model that minimizes the total cost construction and reinforcement substations feeders. The resulted expansion plan designed by this not necessarily best choice for an electrical company (DISCO) in nowadays deregulated structure. This happening mainly due to fact utility seeks maximize its profit competitive environment. On other hand, does consider upcoming new challenges ahead systems, such as smart...
This paper introduces an amendment to radio interferometric calibration of sources below the noise level. The main idea is employ information stronger sources' measured signals as a plug-in criterion solve for weaker ones. For this purpose, we construct number source clusters, with centroids mainly near strongest sources, assuming that belonging single cluster are corrupted by almost same errors. Due characteristic each calibrated source, using all coherencies its simultaneously. obtained...