arXiv subjects

Mukhtar Hussain

Publications and source records attributed to Mukhtar Hussain.

12 recordsLinked to original sources

arXiv2026

Nonlinear Photoemission for Bright Beams in X-Band Photoinjectors

The ongoing development of low-cost and compact x-ray light sources is vital for increasing the number of experiments that can be performed at the atomic scale. Smaller sources can be operated in blow-out mode, in which a high-charge, short-bunch length electron beam self compresses into a uniformly ellipsoidal shape. This mode necessitates a photoinjector whose laser has a pulse duration on the order of $10^2$ fs. In this case, linear photoemission with an ultraviolet laser presents significant technical challenges, as many optical substrates degrade at these wavelengths. In this paper, we present an alternative design that uses nonlinear photoemission to produce electron beams with high charge and short bunch length. This photoinjector design produces an electron beam with a bunch charge of up to $200$ pC, an RMS bunch length of $140$ fs, a normalized transverse emittance of $1$ to $1.4$ mm$\cdot$mrad, and an energy spread of $10^{-4}$. This results in a beam brightness of $9.74\times10^{18}$ A/m$^2$, which is bright enough for our beamline's purposes. Ongoing efforts are aimed at further increasing the electron beam brightness by using a spatial light modulator to shape the laser

physics.optics↗

arXiv2026

A fine-grained attention and geometric correspondence model for musculoskeletal risk classification in athletes using multimodal visual and skeletal features

Musculoskeletal disorders pose significant risks to athletes, and early risk assessment is essential for prevention. However, most existing methods are designed for controlled settings and fail to reliably assess risk in complex environments due to their reliance on a single type of data. This research introduces ViSK-GAT (Visual-Skeletal Geometric Attention Transformer), a novel multimodal deep learning framework that classifies musculoskeletal risk using both visual and skeletal coordinate-based features. A custom multimodal dataset (MusDis-Sports) was created by combining images and skeletal coordinates, with each sample labeled into eight risk categories based on the Rapid Entire Body Assessment (REBA) system. ViSK-GAT integrates two innovative modules: the Fine-Grained Attention Module (FGAM), which refines intra-modal features through self-attention before fusion, and the Multimodal Geometric Correspondence Module (MGCM), which enhances cross-modal alignment between image features and coordinates. The model achieved robust performance, with all key metrics exceeding 93%. Probability distribution error metrics also showed a low Root Mean Squared Error (RMSE) of 0.1205 and a Mean Absolute Error (MAE) of 0.0156. ViSK-GAT consistently outperformed state-of-the-art (SOTA) deep learning backbones and showed its potential to advance artificial intelligence-driven musculoskeletal risk assessment and enable timely interventions in sports.

cs.CV↗

arXiv2026

Mitigating hallucinations in healthcare LLMs with granular fact-checking and domain-specific adaptation

In healthcare, it is essential for any Large Language Model (LLM)-generated output to be reliable and accurate, particularly in cases involving decision-making and patient safety. However, the outputs are often unreliable in such critical areas due to the risk of hallucinated outputs from the LLMs. To address this issue, we propose a fact-checking module that operates independently of any LLM, along with a domain-specific summarization model designed to minimize hallucination rates. Our model is fine-tuned using Low-Rank Adaptation (LoRA) on the MIMIC-III dataset and is paired with the fact-checking module, which uses numerical tests for correctness and logical checks at a granular level through discrete logic in natural language processing (NLP) to validate facts against electronic health records (EHRs). We trained the LLM on the full MIMIC-III dataset. For evaluation of the fact-checking module, we sampled 104 summaries, extracted them into 3786 propositions, and used these as facts. The fact-checking module achieves a precision of 0.8904, a recall of 0.8234, and an F1-score of 0.8556. Additionally, the LLM summary achieves a ROUGE-1 score of 0.5797 and a BERTScore of 0.9120 for summary quality.

cs.CL↗

arXiv2025

From Language to Action: A Review of Large Language Models as Autonomous Agents and Tool Users

The pursuit of human-level artificial intelligence (AI) has significantly advanced the development of autonomous agents and Large Language Models (LLMs). LLMs are now widely utilized as decision-making agents for their ability to interpret instructions, manage sequential tasks, and adapt through feedback. This review examines recent developments in employing LLMs as autonomous agents and tool users and comprises seven research questions. We only used the papers published between 2023 and 2025 in conferences of the A* and A rank and Q1 journals. A structured analysis of the LLM agents' architectural design principles, dividing their applications into single-agent and multi-agent systems, and strategies for integrating external tools is presented. In addition, the cognitive mechanisms of LLM, including reasoning, planning, and memory, and the impact of prompting methods and fine-tuning procedures on agent performance are also investigated. Furthermore, we evaluated current benchmarks and assessment protocols and have provided an analysis of 68 publicly available datasets to assess the performance of LLM-based agents in various tasks. In conducting this review, we have identified critical findings on verifiable reasoning of LLMs, the capacity for self-improvement, and the personalization of LLM-based agents. Finally, we have discussed ten future research directions to overcome these gaps.

cs.CL↗

arXiv2022

Self-probed ptychography from semiconductor high-harmonic generation

We demonstrate a method to image an object using a self-probing approach based on semiconductor high-harmonic generation. On one hand, ptychography enables high-resolution imaging from the coherent light diffracted by an object. On the other hand, high-harmonic generation from crystals is emerging as a new source of extreme-ultraviolet ultrafast coherent light. We combine these two techniques by performing ptychography measurements with nano-patterned crystals serving as the object as well as the generation medium of the harmonics. We demonstrate that this strong field in situ approach can provide structural information about the object. With the future developments of crystal high harmonics as a compact short-wavelength light source, our demonstration can be an innovative approach for nanoscale imaging of photonic and electronic devices in research and industry.

physics.optics↗

arXiv2021

Design Simulation of Czerny-Turner Configuration-based Raman Spectrometer using physical optics propagation algorithm

We report the design simulation of the Raman spectrometer using optical system design software Zemax. The design is based on the Czerny-turner configuration which includes an optical system consisting of an entrance slit, two concave mirrors, reflecting type diffraction grating, and an image detector. The system's modelling approach is suggested by introducing the corresponding relationship between detector pixels and wavelength, linear CCD receiving surface length, and image surface dimension. Simulations have been carried out using the POP (Physical Optics Propagation) algorithm. Spot diagram, relative illumination, irradiance plot, Modulation Transfer Function (MTF), geometric, and encircled energy simulated for designing the Raman spectrometer. The simulation results of the Raman spectrometer's using a 527 nm wavelength laser as an excitation light source are presented. The present optical system is designed in sequential mode and a Raman spectrum observed in the range of 530 to 630 nm. The analysis shows that the system's image efficiency is higher, predicting that it is possible to build an efficient and cost-effective Raman spectrometer for optical diagnostics.

physics.optics↗

arXiv2021

Non-linear propagation effects of intense femtosecond pulses on low order harmonics in solids

The non-linear propagation of the intense near-infrared (NIR) driving field in wide bandgap materials pose a challenge and an opportunity to control the spectral properties of high harmonic generation (HHG) in solids. Here, we have investigated the non-linear propagation effects of the ultrafast intense near-infrared (NIR) driving field at 800 nm of 40 fs pulse duration operating at a repetition rate of 1 kHz focused on the wide bandgap dielectrics such as MgO, Chromium (Cr) doped MgO (Cr: MgO), Sapphire (Sa) crystals and fused silica (FS). Furthermore, we have generated second and third harmonic (TH) in these materials to explore the non-linear response at a strong field. To quantify the non-linear propagation effects, low-order harmonics have been generated in reflection and compared with the harmonics generated in transmission. We observe spectral shifts and broadening of the driving field spectrum which is imprinted on the harmonics. We attribute these effects to strong photoionization, generation of free-carrier density and self-phase modulation effects. We have also studied the polarization dependence of second harmonic generation (SHG) and TH in FS. The linear polarization dependence of below bandgap harmonics in FS and Sa generated in reflection demonstrated the sharp anisotropy than in transmission. This work shows the sensitivity to control the spectral profile of harmonics by manipulating the driving field, showing the possibility of new tailored solid-state XUV sources for optical diagnostics.

physics.optics↗

arXiv2020

Controlling the nonlinear optical properties of MgO by tailoring the electronic structure

The study of the non-linear response of matter to high electric fields has recently encompassed harmonic generation in solids at near-infrared (NIR) driving wavelengths. Interest has been driven by the prospect of ultrafast signal processing and all-optical mapping of electron wave-functions in solids. Engineering solid-state band structures to control the non-linear process has already been highlighted theoretically. Here, we show experimentally for the first time that second harmonic generation (SHG) can be enhanced by doping crystals of magnesium oxide (MgO) with chromium (Cr) atoms. We show that the degree of enhancement depends non-linearly on dopant concentration. The SHG efficiency is shown to increase when Cr dopants are introduced into pure MgO. A physical picture of the effect of Cr dopants is aided by density functional theory (DFT) calculations of the electronic structure for pure and doped samples. This work shows an unambiguous enhancement of the SHG efficiency by modifying the electronic structure. The observed effects are consistent with an electronic structure that facilitates the surface induced SHG and demonstrates a minimal angular dependence. This work highlights the potential of manipulating the electronic structure of solids to control or test theories of their non-linear optical response.

physics.optics↗

arXiv2019

Thermal lensing measurements of Ti: Sapphire crystal pumped at 80 MHz picosecond pulses by Shack-Hartmann wavefront sensor

The thermal lensing effects in the lasing crystal appear to be dominant when the pump laser focused on the lasing crystal which causes the local heating effect. The spatial refractive index variations observed if the crystal has non-uniform temperature distribution. In the present study, the demonstration of thermal lensing effect of Brewster-cut Ti: Sapphire crystal carried out when pumped by 25 ps pulses at 80 MHz repetition rate with 532 nm central wavelength, while the average pump power controlled by the attenuator. The thermal lensing effects measured first at the ~293 K temperature and later at ~40 K by using the cryogenic cooling system. The thermal lensing variations at different average pump power were calculated and measured by using the HASO4 Shack-Hartmann wavefront sensor.

physics.optics↗

arXiv2018

Design and characterization simulation of Ti: sapphire-based femtosecond laser system using Lab2 tools in the NI LabView

We report on the 825-nm center wavelength, 9.17 mJ pulse energy Ti:sapphire-based femtosecond laser system simulation carried out by Lab2 tools in LabVIEW (National Instruments, Inc.). The design investigation and characterization of stretched, amplified and compressed pulses made by intensity module and second harmonic generation (SHG) frequency-resolved optical gating (FROG) module in Lab2. The minimum pulse duration of ~37.80 fs at the output of the compressor end obtained by simulations. The variation of pulse energy, FWHM and central wavelength versus number of passes in the amplifier are computed. The lab2 tools help to design and characterize laser system before to set up on the optical table. The simulation results save time to calculate parameters which are essential in femtosecond laser system designing. The Lab2 simulation tools, along with financial constraints, it is easier, simple and efficient to obtain results in short time.

physics.ins-det↗

arXiv2009

A Novel Two-Staged Decision Support based Threat Evaluation and Weapon Assignment Algorithm, Asset-based Dynamic Weapon Scheduling using Artificial Intelligence Techinques

Surveillance control and reporting (SCR) system for air threats play an important role in the defense of a country. SCR system corresponds to air and ground situation management/processing along with information fusion, communication, coordination, simulation and other critical defense oriented tasks. Threat Evaluation and Weapon Assignment (TEWA) sits at the core of SCR system. In such a system, maximal or near maximal utilization of constrained resources is of extreme importance. Manual TEWA systems cannot provide optimality because of different limitations e.g.surface to air missile (SAM) can fire from a distance of 5Km, but manual TEWA systems are constrained by human vision range and other constraints. Current TEWA systems usually work on target-by-target basis using some type of greedy algorithm thus affecting the optimality of the solution and failing in multi-target scenario. his paper relates to a novel two-staged flexible dynamic decision support based optimal threat evaluation and weapon assignment algorithm for multi-target air-borne threats.

cs.AI↗

arXiv2009

A Novel Two-Stage Dynamic Decision Support based Optimal Threat Evaluation and Defensive Resource Scheduling Algorithm for Multi Air-borne threats

This paper presents a novel two-stage flexible dynamic decision support based optimal threat evaluation and defensive resource scheduling algorithm for multi-target air-borne threats. The algorithm provides flexibility and optimality by swapping between two objective functions, i.e. the preferential and subtractive defense strategies as and when required. To further enhance the solution quality, it outlines and divides the critical parameters used in Threat Evaluation and Weapon Assignment (TEWA) into three broad categories (Triggering, Scheduling and Ranking parameters). Proposed algorithm uses a variant of many-to-many Stable Marriage Algorithm (SMA) to solve Threat Evaluation (TE) and Weapon Assignment (WA) problem. In TE stage, Threat Ranking and Threat-Asset pairing is done. Stage two is based on a new flexible dynamic weapon scheduling algorithm, allowing multiple engagements using shoot-look-shoot strategy, to compute near-optimal solution for a range of scenarios. Analysis part of this paper presents the strengths and weaknesses of the proposed algorithm over an alternative greedy algorithm as applied to different offline scenarios.

cs.AI↗