A5026096668- Radio Astronomy Observations and Technology
- Astrophysics and Cosmic Phenomena
- Galaxies: Formation, Evolution, Phenomena
- Antenna Design and Optimization
- Astronomy and Astrophysical Research
- Astronomical Observations and Instrumentation
- Soil Moisture and Remote Sensing
- Stellar, planetary, and galactic studies
- Geophysics and Gravity Measurements
- Scientific Research and Discoveries
- Radiomics and Machine Learning in Medical Imaging
- Microwave Engineering and Waveguides
- COVID-19 diagnosis using AI
- AI in cancer detection
- Radio Wave Propagation Studies
- Digital Imaging for Blood Diseases
- ECG Monitoring and Analysis
- Advanced Data Compression Techniques
- Brain Tumor Detection and Classification
- Semantic Web and Ontologies
- Cell Image Analysis Techniques
- Gamma-ray bursts and supernovae
- Handwritten Text Recognition Techniques
- Medical Image Segmentation Techniques
- Electromagnetic Simulation and Numerical Methods
BGC Trust University Bangladesh
2024
Rangamati Science and Technology University
2024
McGill University
2022-2024
Innovative Research (United States)
2024
PRG S&Tech (South Korea)
2024
Chandigarh University
2021-2023
Indian Institute of Technology Indore
2019-2022
Indian Institute of Technology Kharagpur
1989-2010
Abstract We report the detection of 21 cm emission at an average redshift <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" overflow="scroll"> <mml:mover accent="true"> <mml:mrow> <mml:mi>z</mml:mi> </mml:mrow> <mml:mo>¯</mml:mo> </mml:mover> <mml:mo>=</mml:mo> <mml:mn>2.3</mml:mn> </mml:math> in cross-correlation data from Canadian Hydrogen Intensity Mapping Experiment (CHIME) with measurements Ly α forest eBOSS. Data collected by CHIME over 88 days 400–500 MHz frequency band (1.8...
Large language models (LLMs) have shown impressive capabilities in natural processing tasks, including dialogue generation. This research aims to conduct a novel comparative analysis of two prominent techniques, fine-tuning with LoRA (Low-Rank Adaptation) and the Retrieval-Augmented Generation (RAG) framework, context doctor-patient chat conversations multiple datasets mixed medical domains. The involves three state-of-the-art models: Llama-2, GPT, LSTM model. Employing real-world dialogues,...
Understanding the low-frequency radio sky in depth is necessary to subtract foregrounds order detect redshifted 21 cm signal of neutral hydrogen from Cosmic Dawn, Epoch Reionization (EoR) and post-reionization era. In this second paper series, we present upgraded Giant Metrewave Radio Telescope (uGMRT) observation ELAIS N1 field made at 300-500 MHz. The image covers an area $\sim 1.8$ $\mathrm{deg}^{2}$ has a central background rms noise $\sim$ 15 $\mu \mathrm{Jy}$ $\mathrm{beam}^{-1}$. We...
As part of the GLOSTAR survey we have used VLA in its B-configuration to observe Galactic plane between longitudes 28d and 36d latitudes from -1d +1d at C-band (4--8 GHz). To reduce contamination extended sources that are not well recovered by our coverage (u, v)-plane discarded short baselines sensitive emission on angular scales $<4"$. The resulting radio continuum images an resolution 1.0", sensitivity $\sim60 \mu$Jy~beam$^{-1}$; making it most covering a large area with this resolution....
Abstract Measurement of fluctuations in diffuse H i 21 cm background radiation from the post-reionization epoch ( z ≤ 6) is a promising avenue to probe large-scale structure universe and understand evolution galaxies. We observe European Large Area ISO Survey-North 1 (ELAIS-N1) field at 300–500 MHz using upgraded Giant Meterwave Radio Telescope (uGMRT) employ “foreground avoidance” technique estimate power spectrum redshift range = 1.96–3.58. Given possible systematics that may remain data,...
In this first paper of the series, we present initial results newly upgraded Giant Meterwave Radio Telescope (uGMRT) observation European Large-Area ISO Survey-North 1 (ELAIS-N1) at 325 MHz with 32 bandwidth. Precise measurement fluctuations in Galactic and extragalactic foreground emission as a function frequency well angular scale is necessary for detecting redshifted 21-cm signal neutral hydrogen from Cosmic Dawn, Epoch Reionization (EoR) post-reionization epoch. Here, time have...
We report the first $5\sigma$ detection of HI 21 cm emission from a star-forming galaxy at redshift $z\sim1.3$ (nearly 9 billion years ago) using upgraded Giant Metrewave Radio Telescope (uGMRT). This is highest in an individual to date. The strongly boosted by gravitational lens, early type elliptical galaxy, $z \sim 0.13$. measured mass $\rm M_{HI} = (0.90 \pm 0.14 0.05) \times 10^{10}M_{\odot}$, which almost twice inferred stellar indicating extended structure gas inside galaxy. By...
One of the key science goals for most sensitive telescopes, both current and upcoming, is detection redshifted 21-cm signal from Cosmic Dawn Epoch Reionization. The success relies on accurate foreground modeling their removal data sets. This paper presents characterization astrophysical sources in Lockman Hole region. Using 325 MHz obtained GMRT, a $6^\circ \times 6^\circ$ mosaiced map produced with an RMS reaching 50 $\mu$Jy $\mathrm{beam}^{-1}$. A source catalog containing 6186 created,...
ABSTRACT Observation of the redshifted 21-cm signal from Cosmic Dawn and Epoch Reionization is a challenging endeavor in observational cosmology. Presence orders magnitude brighter astrophysical foregrounds various instrumental systematics increases complexity these observations. This work presents an end-to-end pipeline dealing with synthetic interferometric data sensitive radio The mock sky model includes foregrounds. effects calibration error position extraction power spectrum has been...
ABSTRACT Neutral hydrogen (${\rm H\, \small {I}}$) 21-cm intensity mapping (IM) is a promising probe of the large-scale structures in Universe. However, few orders magnitude brighter foregrounds obscure IM signal. Here, we use tapered gridded estimator to estimate multifrequency angular power spectrum Cℓ(Δν) from $24.4\hbox{-} \rm {MHz}$ bandwidth upgraded Giant Metrewave Radio Telescope Band 3 data at $432.8\ {MHz}$. In remain correlated across entire Δν range, whereas signal localized...
Abstract Power spectrum of H i 21-cm radiation is one the promising probes to study large scale structure universe and understand galaxy formation evolution. The presence foregrounds, that are orders magnitude larger in same frequency range redshifted signal has been largest observational challenges. foreground contamination also hinders calibration procedures introduces residual errors interferometric data. It shown can introduce bias power estimates additional systematics. In this work, we...
Abstract We present the first results of holographic beam-mapping program for Canadian Hydrogen Intensity Mapping Experiment (CHIME). describe implementation a technique as adapted CHIME, and introduce processing pipeline which prepares raw timestreams analysis beam features. use data from six bright sources across full 400–800 MHz observing band CHIME to provide measurements copolar cross-polar response in both amplitude phase all 1024 dual-polarized feeds array. In addition, we comparisons...
The continuum emission from 1 to 2 GHz of HI/OH/Recombination line survey the inner Milky Way (THOR) at $\lesssim$18" resolution covers $\sim 132$ square degrees Galactic plane and detects 10387 sources. Similarly, first data release Global View Star Formation in (GLOSTAR) surveys 16$ 4-8 18" 1575 However, a large fraction unresolved discrete sources detected these radio remain unclassified. Here, we study Euclidean-normalized differential source counts unclassified compare them with...
ABSTRACT Comprehending the radio–infrared (IR) relations of faint extragalactic radio sources is important for using emission as a tracer star formation in high redshift (z) star-forming galaxies (SFGs). Using deep uGMRT observations ELAIS-N1 field 0.3–0.5 GHz range, we study statistical properties radio–IR and variation ‘q-parameter’ up to z = 2 after broadly classifying SFGs AGN. We find dust temperature (Tdust) increase with z. This gives rise $q_{\rm 24\,\mu m}$, measured at $24\, \mu$m,...
The cosmic evolution of bias different source populations with underlying dark matter density field in post reionization era can shed light on large scale structures. Studying the angular and spatial distribution compact sources using deep radio catalogue at low-frequency is essential to understand present Universe. Here, we investigate relationship luminous their host haloes by measuring clustering (two-point statistics), observation ELAIS N1 (EN1) upgraded Giant Metrewave Radio Telescope...
The study of the cosmic Dark Ages, Cosmic Dawn, and Epoch Reionization (EoR) using all-sky averaged redshifted HI 21cm signal, are some key science goals most ongoing or upcoming experiments, for example, EDGES, SARAS, SKA. This signal can be detected by averaging over entire sky, a single radio telescope, in form Global as function only frequencies. One major challenges faced while detecting this is dominating, bright foreground. success such detection lies accuracy foreground removal....
Neutral hydrogen ($\rm{HI}$) $21$-cm intensity mapping (IM) offers an efficient technique for the large-scale structures in universe. We introduce 'Cross' Tapered Gridded Estimator (Cross TGE), which cross-correlates two cross-polarizations (RR and LL) to estimate multi-frequency angular power spectrum (MAPS) $C_{\ell}(\Delta\nu)$. expect this mitigate several effects like noise bias, calibration errors etc., affect 'Total' TGE combines polarizations. Here we apply Cross on a $24.4...
We investigate the effect of radio-frequency interference (RFI) excision in estimating cosmological \hi\ 21 cm power spectrum. Flagging RFI-contaminated channels results a non-uniform sampling instrumental bandpass response. Hence, Fourier transformation (FT) visibilities from frequency to delay domain contaminates higher foreground-free modes, and separating spectrally fluctuating signal smooth foregrounds becomes challenging. have done comparative analysis between two algorithms,...
ABSTRACT The post-reionization (z ≤ 6) neutral hydrogen (H i) 21-cm intensity mapping signal holds the potential to probe large-scale structures, study expansion history, and constrain various cosmological parameters. Here, we apply Tapered Gridded Estimator (TGE) estimate P(k⊥, k∥) power spectrum of $z = 2.28\, (432.8\, {\rm MHz})$ redshifted using a $24.4\, MHz}$ sub-band drawn from uGMRT Band 3 observations European Large-Area ISO Survey-North 1 (ELAIS-N1). TGE allows us taper sky...
Brain Tumor diagnosis at early stage can play a critical role in the prognosis of patient. Magnetic resonance (MR) imaging is regarded as present state-of-the-art technique for brain tumor diagnosis. There has been significant work done to identify using computer-aided diagnostic model via both hand-crafted an deep learning based approaches. However, due variability contrast and distortion MR images, identification BT becomes challenging. The ExRAN ensemble all pretrained network i.e....
An analysis is presented of a T junction between rectangular and circular waveguides coupled through long axial slot in the narrow wall waveguide. A moment method with entire orthogonal basis functions used for deriving expressions elements scattering matrix. The effect thickness taken into account by treating coupling as short section waveguide matching boundary conditions at interfaces. satisfied matrix are verified. comparison theoretical experimental results on variation frequency...
Studying the spatial distribution of extragalactic source populations is vital in understanding matter Universe. It also enables cosmological evolution dark density fields and relationship between luminous matter. Clustering studies are required for EoR foreground since it affects relevant angular scales. This paper investigates clustering properties bias parameter radio-selected sources Lockman Hole field at 325 MHz. The data probes with fluxes $\gtrsim$0.3 mJy within a radius 1.8$^\circ$...
We present a Wideband Tapered Gridded Estimator (TGE), which incorporates baseline migration and variation of the primary beam pattern for neutral hydrogen (${\rm H\hspace{0.5mm}}{\scriptsize {\rm I}}$) 21-cm intensity mapping (IM) with large frequency bandwidth radio-interferometric observations. Here we have analysed $394-494 \, MHz}$ $(z = 1.9 - 2.6)$ uGMRT data to estimate Multi-frequency Angular Power Spectrum (MAPS) $C_\ell(\Delta\nu)$ from removed foregrounds using polynomial fitting...
Counterfeiting poses a significant threat to the stability of Bangladesh's currency, Taka, necessitating advanced methods for detection and prevention. This paper presents an innovative approach counterfeit using Convolutional Neural Networks (CNNs), deep learning technology. Explicitly focused on this method aims enhance accuracy efficiency by leveraging power artificial intelligence. The proposed involves training CNNs dataset authentic Bangladeshi currency images, allowing network learn...