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Amanpreet Kaur

Publications and source records attributed to Amanpreet Kaur.

At least 19 recordsLinked to original sources

Pre-Deployment Robustness Stress Testing for CT Segmentation Systems Using Clinically Motivated Multi-Corruption Augmentation

Deep learning-based CT segmentation systems often achieve high accuracy on clean benchmark images, but their performance may degrade under heterogeneous clinical imaging conditions such as noise, resolution loss, contrast variation, intensity shift, and artifacts. This instability can limit reliable deployment in real-world medical imaging workflows. We propose Robustness via Augmented Multi-corruption Pipeline (RAMP), a robustness-oriented augmentation framework for CT segmentation. RAMP combines anatomically constrained spatial perturbations, CT intensity transformations, and stochastic multi-corruption composition to expose models to clinically plausible image degradation during training. Across two CT segmentation evaluation settings, RAMP achieved the strongest corrupted-image performance and the smallest clean-to-corrupted robustness gap. In the five-organ noisy evaluation benchmark, RAMP improved mean corrupted Dice from 0.610 to 0.753 and reduced the robustness gap from 0.264 to 0.064 compared with the nnU-Net baseline. In Abdomen1K, RAMP improved mean corrupted Dice from 0.633 to 0.789 and reduced the robustness gap from 0.290 to 0.070. Although RAMP did not achieve the highest clean-image Dice, it substantially mitigated worst-case segmentation collapse under severe image degradation. These results suggest that multi-corruption augmentation can serve as a practical pre-deployment strategy for improving the reliability of CT segmentation systems in heterogeneous clinical environments.

cs.CV

Generative AI and Digital Ecosystem Resilience: A Proactive Lifecycle-Based Survey

The proliferation of adversarial synthetic content, accelerated by Generative AI (GenAI) is rendering traditional reactive detection methods ineffective. This survey synthesizes emerging research to demonstrate a paradigm shift toward the proactive detection of emerging inauthentic narratives. In this survey, we adopt a unified, lifecycle-based taxonomy to combine socio-technical lifecycle models of adversarial campaigns with advanced computational methodologies for emerging inauthentic narrative detection. By structuring the analysis around the C5 Interaction Model (Context, Causes, Content, Cycle of Amplification, Consequences), we integrate different research streams from machine learning and social science. To differentiate spread patterns of synthetic amplification from authentic baseline traffic, this paper surveys state-of-the-art techniques for modeling the creation, seeding, and propagation of fresh narratives, including the analysis of Coordinated Inauthentic Behavior (CIB), epidemiological modeling, and Hawkes process. This survey also provides a systematic review of proactive detection methods for adversarial threats at different stages in the C5 interaction model, specifically, anomaly detection in high-dimensional embedding spaces, unsupervised coordination detection on multi-layer graphs, and agentic AI systems. Finally, this survey addresses challenges posed by GenAI, including the difficulty of tracking rapidly changing threats and multi-level distributional drift, and it outlines a future research agenda focused on detecting anomalous clusters and building anticipatory and resilient systems. This survey provides a comprehensive, lifecycle-based review of methods for the proactive detection of emerging synthetic threats for more resilient information ecosystems.

cs.LG

High-gain MIMO Beamforming Antenna System for DSRC and mmwave 5G Integration in Autonomous Vehicles

The evolution of autonomous vehicles necessitates robust, high-speed, and low-latency wireless communication systems. This paper presents a novel high-gain Multiple-Input Multiple-Output (MIMO) beamforming antenna system that concurrently supports Dedicated Short Range Communications (DSRC) at 5.9 GHz and millimeter-wave (mm Wave) 5G communications at 28 GHz. The proposed design addresses challenges such as compactness, dual-band operation, beam steering capability, and port-to-port isolation within dynamic vehicular environments.

eess.SP

Using Neural Networks to Differentiate Newly Discovered BL Lacs and FSRQs among the 4FGL Unassociated Sources Employing Gamma-ray, X-ray, UV/Optical and IR Data

Among the ~2157 unassociated sources in the third data release (DR3) of the fourth Fermi catalog, ~1200 were observed with the Neil Gehrels Swift Observatory pointed instruments. These observations yielded 238 high S/N X-ray sources within the 95% Fermi uncertainty regions. Recently, Kerby et al. employed neural networks to find blazar candidates among these 238 X-ray counterparts to the 4FGL unassociated sources and found 112 likely blazar counterpart sources. A complete sample of blazars, along with their sub-classification, is a necessary step to help understand the puzzle of the blazar sequence and for the overall completeness of the gamma-ray emitting blazar class in the Fermi catalog. We employed a multi-perceptron neural network classifier to identify FSRQs and BL Lacs among these 112 blazar candidates using the gamma-ray, X-ray, UV/optical, and IR properties. This classifier provided probability estimates for each source to be associated with one or the other category, such that P_fsrq represents the probability for a source to be associated with the FSRQ subclass. Using this approach, 4 FSRQs and 50 BL Lacs are classified as such with >99% confidence, while the remaining 58 blazars could not be unambiguously classified as either BL Lac or FSRQ.

astro-ph.HE

Modeling the Spectral Energy Distributions and Spectropolarimetry of Blazars -- Application to 4C+01.02 in 2016-2017

The optical radiation emitted by blazars contains contributions from synchrotron radiation by relativistic electrons in the jets, as well as thermal radiation emitted mainly by the Accretion Disk (AD), the Broad Line Region (BLR) and the host galaxy. The unpolarized radiation components from the AD, BLR and host galaxy present themselves by decreasing the total polarization in the optical/ultraviolet(UV) spectrum. A combined model for the Spectral Energy Distribution (SED) and degree of optical/UV polarization is constructed, enabling the disentanglement of the synchrotron and AD components. Our model is applied to the multi-wavelength SED and spectropolarimetry observations of the Flat Spectrum Radio Quasar 4C+01.02 ($z = 2.1$) in its 2016 July-August flaring state and July-August 2017 quiescent state, using data from the Fermi Large Area Telescope, the Southern African Large Telescope and the Las Cumbres Observatory network of telescopes. By constraining the AD component, the mass of the super massive black hole is obtained as $3 \times 10^9 \rm M_{\odot}$. Furthermore, the model retrieves the characteristics of the relativistic electron distribution in the jet and the degree of ordering of the magnetic field. Our results highlight the potential of spectropolarimetry observations for disentangling thermal from non-thermal (jet) emission components and thus revealing the physics of particle acceleration and high-energy emission in active galactic nuclei jets.

astro-ph.HE

Multiwavelength Spectral Analysis and Neural Network Classification of Counterparts to 4FGL Unassociated Sources

The Fermi-LAT unassociated sources represent some of the most enigmatic gamma-ray sources in the sky. Observations with the Swift-XRT and -UVOT telescopes have identified hundreds of likely X-ray and UV/optical counterparts in the uncertainty ellipses of the unassociated sources. In this work we present spectral fitting results for 205 possible X-ray/UV/optical counterparts to 4FGL unassociated targets. Assuming that the unassociated sources contain mostly pulsars and blazars, we develop a neural network classifier approach that applies gamma-ray, X-ray, and UV/optical spectral parameters to yield descriptive classification of unassociated spectra into pulsars and blazars. From our primary sample of 174 Fermi sources with a single X-ray/UV/optical counterpart, we present 132 P_bzr > 0.99 likely blazars and 14 P_bzr < 0.01 likely pulsars, with 28 remaining ambiguous. These subsets of the unassociated sources suggest a systematic expansion to catalogs of gamma-ray pulsars and blazars. Compared to previous classification approaches our neural network classifier achieves significantly higher validation accuracy and returns more bifurcated P_bzr values, suggesting that multiwavelength analysis is a valuable tool for confident classification of Fermi unassociated sources.

astro-ph.HE

X-ray Spectra and Multiwavelength Machine Learning Classification for Likely Counterparts to Fermi 3FGL Unassociated Sources

We conduct X-ray spectral fits on 184 likely counterparts to Fermi-LAT 3FGL unassociated sources. Characterization and classification of these sources allows for more complete population studies of the high-energy sky. Most of these X-ray spectra are well fit by an absorbed power law model, as expected for a population dominated by blazars and pulsars. A small subset of 7 X-ray sources have spectra unlike the power law expected from a blazar or pulsar and may be linked to coincident stars or background emission. We develop a multiwavelength machine learning classifier to categorize unassociated sources into pulsars and blazars using gamma- and X-ray observations. Training a random forest procedure with known pulsars and blazars, we achieve a cross-validated classification accuracy of 98.6%. Applying the random forest routine to the unassociated sources returned 126 likely blazar candidates (defined as $ P_{bzr} > 90 \% $) and 5 likely pulsar candidates ($ P_{bzr} < 10 \% $). Our new X-ray spectral analysis does not drastically alter the random forest classifications of these sources compared to previous works, but it builds a more robust classification scheme and highlights the importance of X-ray spectral fitting. Our procedure can be further expanded with UV, visual, or radio spectral parameters or by measuring flux variability.

astro-ph.HE

Classifying blazar candidates from the 3FGL unassociated catalog into BL Lacs and FSRQs using Swift and WISE data

We utilize machine learning methods to distinguish BL Lacertae objects (BL Lac) from Flat Spectrum Radio Quasars (FSRQ) within a sample of likely X-ray blazar counterparts to Fermi 3FGL unassociated gamma-ray sources. From our previous work, we have extracted 84 sources that were classified as $\geq$ 99% likley to be blazars. We then utilize Swift$-$XRT, Fermi, and WISE (The Wide-field Infrared Survey Explorer) data together to distinguish the specific type of blazar, FSRQs or BL Lacs. Various X-ray and Gamma-ray parameters can be used to differentiate between these subclasses. These are also known to occupy different parameter space on the WISE color-color diagram. Using all these data together would provide more robust results for the classified sources. We utilized a Random Forest Classifier to calculate the probability for each blazar to be associated with a BL Lac or an FSRQ. Based on P$_{bll}$, which is the probability for each source to be a BL Lac, we placed our sources into five different categories based on this value as follows; P$_{bll}$ $\geq$ 99%: highly likely BL Lac, P$_{bll}$ $\geq$ 90%: likely BL Lac, P$_{bll}$ $\leq$ 1%: highly likely FSRQ, P$_{bll}$ $\leq$ 10%: likely FSRQ, and 90% $<$ P$_{bll}$ $<$ 10%: ambiguous. Our results categorize the 84 blazar candidates as 50 likely BL Lacs and the rest 34 being ambiguous. A small subset of these sources have been listed as associated sources in the most recent Fermi catalog, 4FGL, and in these cases our results are in agreement on the classification.

astro-ph.HE

Blazars at the Cosmic Dawn

The uncharted territory of the high-redshift ($z\gtrsim3$) Universe holds the key to understand the evolution of quasars. In an attempt to identify the most extreme members of the quasar population, i.e., blazars, we have carried out a multi-wavelength study of a large sample of radio-loud quasars beyond $z=3$. Our sample consists of 9 $γ$-ray detected blazars and 133 candidate blazars selected based on the flatness of their soft X-ray spectra (0.3$-$10 keV photon index $\leq1.75$), including 15 with NuSTAR observations. The application of the likelihood profile stacking technique reveals that the high-redshift blazars are faint $γ$-ray emitters with steep spectra. The high-redshift blazars host massive black holes ($\langle \log~M_{\rm BH,~M{\odot}} \rangle>9$) and luminous accretion disks ($\langle L_{\rm disk} \rangle>10^{46}$ erg s$^{-1}$). Their broadband spectral energy distributions are found to be dominated by high-energy radiation indicating their jets to be among the most luminous ones. Focusing on the sources exhibiting resolved X-ray jets (as observed with the Chandra satellite), we find the bulk Lorentz factor to be larger with respect to other $z>3$ blazars, indicating faster moving jets. We conclude that the presented list of the high-redshift blazars may act as a reservoir for follow-up observations, e.g., with NuSTAR, to understand the evolution of relativistic jets at the dawn of the Universe.

astro-ph.HE

Classification of New X-ray Counterparts for Fermi Unassociated Gamma Ray Sources Using the Swift X-Ray Telescope

Approximately one-third of the gamma-ray sources in the third Fermi-LAT catalog are unidentified or unassociated with objects at other wavelengths. Observations with Swift-XRT have yielded possible counterparts in $\sim$30% of these source regions. The objective of this work is to identify the nature of these possible counterparts, utilizing their gamma ray properties coupled with the Swift derived X-ray properties. The majority of the known sources in the Fermi catalogs are blazars, which constitute the bulk of the extragalactic gamma-ray source population. The galactic population on the other hand is dominated by pulsars. Blazars and pulsars occupy different parameter space when X-ray fluxes are compared with various gamma-ray properties. In this work, we utilize the X-ray observations performed with the Swift-XRT for the unknown Fermi sources and compare their X-ray and gamma-ray properties to differentiate between the two source classes. We employ two machine learning algorithms, decision tree and random forest classifier, to our high signal-to-noise ratio sample of 217 sources, each of which correspond to Fermi unassociated regions. The accuracy score for both methods were found to be 97% and 99%, respectively. The random forest classifier, which is based on the application of a multitude of decision trees, associated a probability value (P$_{bzr}$) for each source to be a blazar. This yielded 173 blazar candidates with P$_{bzr}$ $\geq$ 90% for each of these sources, and 134 of these possible blazar source associations had P$_{bzr}$ $\geq$ 99%. The results yielded 13 sources with P$_{bzr}$ $\leq$ 10%, which we deemed as reasonable candidates for pulsars, 7 of which result with P$_{bzr}$ $\leq$ 1%. There were 31 sources that exhibited intermediate probabilities and were termed ambiguous due to their unclear characterization as a pulsar or a blazar.

astro-ph.HE

Advanced Astrophysics Discovery Technology in the Era of Data Driven Astronomy

Experience suggests that structural issues in how institutional Astrophysics approaches data-driven science and the development of discovery technology may be hampering the community's ability to respond effectively to a rapidly changing environment in which increasingly complex, heterogeneous datasets are challenging our existing information infrastructure and traditional approaches to analysis. We stand at the confluence of a new epoch of multimessenger science, remote co-location of data and processing power and new observing strategies based on miniaturized spacecraft. Significant effort will be required by the community to adapt to this rapidly evolving range of possible discovery moduses. In the suggested creation of a new Astrophysics element, Advanced Astrophysics Discovery Technology, we offer an affirmative solution that places the visibility of discovery technologies at a level that we suggest is fully commensurate with their importance to the future of the field.

astro-ph.IM

Probing an X-ray flare pattern in Mrk 421 induced by multiple stationary shocks: a solution to the bulk Lorentz factor crisis

The common observations of multiple radio VLBI stationary knots in high-frequency-peaked BL Lacs (HBLs) can be interpreted as multiple recollimation shocks accelerating particles along jets. This approach can resolve the so-called "bulk Lorentz factor crisis" of sources with high Lorentz factor, deduced from maximum gamma-gamma opacity and fast variability, and apparently inconsistent slow/stationary radio knots. It also suggests that a unique pattern of the non-thermal emission variability should appear after each strong flare. Taking advantage of the 13 years of observation of the HBL Mrk 421 by the X-ray Telescope on the Neil Gehrels Swift Observatory Swift-XRT, we probe for such an intrinsic variability pattern. Its significance is then statistically estimated via comparisons with numerous similar simulated lightcurves. A suggested variability pattern is identified, consistent with a main flare emission zone located in the most upstream 15.3 GHz radio knot at 0.38 mas from the core. Subsequent flux excesses in the lightcurve are consistent with a perturbation crossing all the downstream radio knots with a constant apparent speed of 45 c. The significance of the observed variability pattern not arising from stochastic processes is found above 3 standard deviations, opening a promising path for further investigations in other blazars and with other energy bands. In addition to highlight the role of stationary radio knots as high-energy particle accelerators in jets, the developed method allows estimates of the apparent speed and size of a jet perturbation without the need to directly observe any motion in jets.

astro-ph.HE

Identifying the 3FHL catalog: I. Archival Swift Observations and Source Classification

We present the results of an identification campaign of unassociated sources from the Fermi Large Area Telescope 3FHL catalog. Out of 200 unidentified sources, we selected 110 sources for which archival Swift-XRT observations were available, 52 of which were found to have exactly one X-ray counterpart within the 3FHL 95\% positional uncertainty. In this work, we report the X-ray, optical, IR, and radio properties of these 52 sources using positional associations with objects in various catalogs. The Wide-field Infrared Survey Explorer color-color plot for sources suggests that most of these belong to the blazar class family. The redshift measurements for these objects range from z=0.277 to z=2.1. Additionally, under the assumption that the majority of these sources are blazars, three machine-learning algorithms are employed to classify the sample into flat spectrum radio quasars or BL Lacertae objects. These suggest that the majority of the previously unassociated sources are BL Lac objects, in agreement with the fact the BL Lac objects represent by far the most numerous population detected above 10 GeV in 3FHL.

astro-ph.HE

Identifying the 3FHL catalog: I. Results of the KOSMOS optical spectroscopy campaign

We present the results of the optical spectroscopy follow-up of a sample of 28 unclassified blazars from the Third Fermi-LAT Catalog of High-Energy Sources (3FHL). All the spectra were taken with the 4m Mayall telescope at Kitt Peak. With this follow-up program we are able to classify 27 out of 28 objects as BL Lacs, while the remaining one is a flat spectrum radio quasar. We determine a redshift (z) for three of these objects and a lower limit on z for other four sources: the farthest object for which we obtain a redshift has z>0.836. These results are part of a more extended campaign of optical spectroscopy follow-up of 3FHL blazars, aimed to obtain a complete sample of blazars at >10 GeV which will then be used to extend our knowledge on blazar emission mechanisms and on the extragalactic background light.

astro-ph.GA

New high-z BL Lacs using the photometric method with Swift and SARA

BL Lacertae (BL Lac) objects are the prominent members of the third {\it Fermi} Large Area Telescope catalog of $γ$-ray sources. Half of the BL Lac population ($\sim$ 300) lack redshift measurements, which is due to the absence of lines in their optical spectrum, thereby making it difficult to utilize spectroscopic methods. Our photometric drop-out technique can be used to establish the redshift for a fraction of these sources. This work employed 6 filters mounted on the $Swift$-UVOT and 4 optical filters on two telescopes, the 0.65 m SARA-CTIO in Chile and 1.0 m SARA-ORM in the Canary Islands, Spain. A sample of 15 sources was extracted from the $Swift$ archival data for which 6 filter UVOT observations were conducted. By complementing the {\it Swift} observations with the SARA ones, we were able to discover two high redshift sources: 3FGL J1155.4-3417 and 3FGL J1156.7-2250 at $z=1.83^{+0.10}_{-0.13}$ and $z=1.73^{+0.11}_{-0.19}$ , respectively, resulting from the dropouts in the powerlaw template fits to these data. The discoveries add to the important (26 total) sample of high-redshift BL Lacs. While the sample of high-z BL Lacs is still rather small, these objects do not seem to fit well within known schemes of the blazar population and represent the best probes of the extragalactic background light.

astro-ph.HE

Properties of JP = 1/2+ baryon octets at low energy

The statistical model in combination with detailed balance principle is able to phenomenological calculate and analyze spin and flavor dependent properties like magnetic moments (with effective masses, effective charge, with both effective mass and effective charge), quark spin polarization and distribution, strangeness suppression factor. The magnetic moments of the octet baryons are analyzed within the statistical model, by putting emphasis on the SU(3) symmetry breaking effects generated by the mass difference between the strange and non strange quarks. The work presented here assume hadrons with a sea having admixture of quark-gluon Fock states. The results obtained have been compared with theoretical models and experimental data.

hep-ph

J/P=1/2+, J/P=3/2+ masses in statistical model

The mass formulae for the baryon octet and decuplet are calculated. These formulae are function of constituent quark masses and spin spin interaction terms for the quarks inside the baryons. The coefficients in the mass formulae is estimated by the statistical model for J/P=1/2+, J/P=3/2+, incorporating the contributions from \sea" containing uu; dd; ss pairs and gluons . The measured masses are presented and found to be matching good with some of the experimental and theoretical data.

hep-ph

Energy Consumption Forecasting for Smart Meters

Earth, water, air, food, shelter and energy are essential factors required for human being to survive on the planet. Among this energy plays a key role in our day to day living including giving lighting, cooling and heating of shelter, preparation of food. Due to this interdependency, energy, specifically electricity, production and distribution became a high tech industry. Unlike other industries, the key differentiator of electricity industry is the product itself. It can be produced but cannot be stored for future; production and consumption happen almost in near real-time. This particular peculiarity of the industry is the key driver for Machine Learning and Data Science based innovations in this industry. There is always a gap between the demand and supply in the electricity market across the globe. To fill the gap and improve the service efficiency through providing necessary supply to the market, commercial as well as federal electricity companies employ forecasting techniques to predict the future demand and try to meet the demand and provide curtailment guidelines to optimise the electricity consumption/demand. In this paper the authors examine the application of Machine Learning algorithms, specifically Boosted Decision Tree Regression, to the modelling and forecasting of energy consumption for smart meters. The data used for this exercise is obtained from DECC data website. Along with this data, the methodology has been tested in Smart Meter data obtained from EMA Singapore. This paper focuses on feature engineering for time series forecasting using regression algorithms and deriving a methodology to create personalised electricity plans offers for household users based on usage history.

cs.OH