Publications

I develop AI-driven models and computational pipelines for drug discovery - QSAR, molecular docking, and deep learning for target identification - alongside portable biomedical devices and biosensing platforms for real-world diagnostics. Below is my publication record grouped by research theme, with full abstracts, keywords, and bibliographic metadata.

32+
Peer-Reviewed Papers
200+
Citations (Google Scholar)
10
h-index
9
AI Drug Discovery Papers
1
Patent Under Examination

Computational Drug Discovery

AI and machine learning applied to therapeutic target identification - deep learning QSAR models and multi-ligand molecular docking to predict activity, selectivity, and mechanism of small-molecule and phytochemical inhibitors.

What is multi-ligand simultaneous docking (MLSD)?

MLSD is a computational technique that docks two or more ligands into a protein's binding pocket at the same time, capturing cooperative or synergistic binding effects that single-ligand docking misses. We used it to show Withaferin A and Garcinol jointly inhibiting BCL-2 and AKT-1 more strongly than either compound alone (Biswas et al., ICE 2025), and Carpaine and Rutin achieving multi-mechanism inhibition of BCL-2 and WWP1 that intensified further when Rutin was combined with the clinical drug bortezomib (Sudha et al., Phytomedicine Plus 2025).

How accurate are QSAR models at predicting new enzyme inhibitors?

Across our QSAR studies, classification accuracy has ranged from 0.81 to over 0.96 depending on target and model architecture - an SVM classifier reached 0.81 accuracy identifying LmGT inhibitors for leishmaniasis (Biswas et al., ICE 2025), while a deep-learning model predicting estrogen receptor-binding endocrine disruptors reached 96.65% training / 91.30% test accuracy (Desai et al., IEEE B-HTC 2026). Every model's top candidates are cross-validated against molecular docking scores before being proposed as inhibitors.

Can plant-derived compounds rival commercial cancer drugs in binding affinity?

In several of our docking studies, natural phytochemicals matched or exceeded commercial inhibitors - Moringa oleifera compounds reached a BCL-2 MLSD binding affinity of −14.96 kcal/mol, surpassing the commercial inhibitor venetoclax (Saha et al., IBIOMED 2024), and Withaferin A with Garcinol exceeded both venetoclax (BCL-2) and melatonin (AKT-1) binding affinities (Biswas et al., ICE 2025).

Advancing Alzheimer's disease treatment: Synergistic ligand combinations targeting BACE1 through multi-ligand simultaneous docking

P. Biswas, S. Shanbhog, M. Sudha, B.M.A. Desai · Advanced Neurology · 2025

Alzheimer's DiseaseBACE1Binding AffinityDrug DiscoveryMolecular DynamicsMulti-Ligand Simultaneous Docking

First application of multi-ligand simultaneous docking to Alzheimer's drug discovery, screening over 15,000 candidate molecules to find inhibitor combinations that block BACE1 more effectively than any single compound.

Key Finding: Combining CHEMBL4078427 with CHEMBL3656158 and lanabecestat produced MLSD binding affinities of −19.90 to −17.67 kcal/mol against BACE1 - well beyond any single-ligand result.

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Alzheimer's disease is a progressive neurodegenerative condition marked by memory loss, cognitive decline, and behavioral changes, with no disease-halting therapies currently available. Recent BACE1-targeting drugs show clinical promise but face limitations including side effects and insufficient efficacy. This research represents the first application of multi-ligand simultaneous docking (MLSD) to identify synergistic inhibitor combinations. Researchers screened 15,641 small molecules with known IC50 values against BACE1, yielding binding affinities ranging from -11.32 to +10.85 kcal/mol. Five compounds with affinities of -11 kcal/mol or better were tested via MLSD. Four tested combinations, including CHEMBL4078427 with CHEMBL3656158 and lanabecestat, demonstrated superior binding affinities (-19.90 to -17.67 kcal/mol) with inter-ligand interactions indicating synergy. Molecular dynamics simulations confirmed enhanced BACE1 inhibition with improved stability metrics compared to single-ligand approaches, suggesting novel combination therapies for Alzheimer's treatment.

Silent Survivors: The Role of Persister Cells in Leishmaniasis and Therapeutic Failure

M. Bhatt, B.M.A. Desai, P. Biswas · ACS Infectious Diseases · 2026

Drug ToleranceHost−Parasite InteractionsImmune EvasionPersister CellsQuiescency and DormancyTreatment Failure and Relapse

A comprehensive review of persister-like Leishmania populations - the phenotypically distinct, drug-tolerant subpopulations behind treatment failure and relapse - synthesizing the molecular pathways, host-parasite interactions, and methodological challenges shaping the search for therapies that target nonreplicating parasite forms.

Key Finding: Identifies L. donovani Zeta-toxin (Ld_ζ1) and dormancy-associated phosphatases as key molecular drivers sustaining drug-tolerant Leishmania persister populations.

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Leishmania spp., the causative agents of leishmaniasis, exhibit complex evolved mechanisms that allow long-term survival within the host despite antileishmanial treatment. This ability is closely associated with the presence of persister-like parasite populations that are phenotypically distinct from actively replicating forms. These subpopulations are capable of reversible drug tolerance without genetic resistance, which allows them to tolerate drug exposure and evade immune mechanisms. Persister-like parasites have been reported in multiple clinical manifestations such as visceral, cutaneous, and post-kala-azar dermal leishmaniasis. These persister-like parasites undergo metabolic slowdown, altered gene expression, and increased stress tolerance. These parasite-intrinsic changes are reinforced by host-parasite interactions within immune-regulated niches, where cytokine signaling, macrophage deactivation, and tissue-specific environments limit effective parasite elimination. Several molecular pathways, such as stress-activated kinases and dormancy-associated regulators, including phosphatases and L. donovani Zeta-toxin (Ld_ζ1) proteins, contribute to the maintenance of this persistent state. This review summarizes the current understanding of Leishmania persistence by integrating mechanistic insights, experimental and clinical observations, methodological challenges, and emerging molecular approaches. It also discusses implications for drug discovery and the limitations of conventional therapies that fail to target nonreplicating forms. Understanding persistence as a biological survival strategy is essential for interpreting treatment failure, relapse, and ongoing transmission and paves the way for more targeted and effective therapeutic interventions.

Deep Learning-based QSAR Model for Therapeutic Strategies Targeting SmTGR Protein's Immune Modulating Role in Host-Parasite Interaction

B.M.A. Desai, B.M. Anirudh, K.S. Biju, V. Ramesh, P. Biswas · 2025 IEEE AMATHE · 2025

AI Accelerated Drug DiscoveryDeep LearningQSARSmTGR

Builds a deep learning QSAR model to predict inhibitors of the SmTGR protein, a target implicated in the host–parasite immune response, aiming to accelerate the discovery of new antiparasitic therapeutics.

Key Finding: Deep learning QSAR + docking identified SmTGR inhibitors with a top docking score of −10.76 ± 0.01 kcal/mol.

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Schistosomiasis, a neglected tropical disease caused by Schistosoma parasites, remains a major global health challenge. The Schistosoma mansoni thioredoxin glutathione reductase (SmTGR) is essential for parasite redox balance and immune evasion, making it a key therapeutic target. This study employs predictive Quantitative Structure-Activity Relationship (QSAR) modeling to identify potential SmTGR inhibitors. Using deep learning, a robust QSAR model was developed and validated, achieving high predictive accuracy. The predicted novel inhibitors were further validated through molecular docking studies, which demonstrated strong binding affinities, with the highest docking score of -10.76 ± 0.01 kcal/mol. Visualization of the docked structures in both 2D and 3D confirmed similar interactions for the inhibitors and commercial drugs, further supporting their therapeutic effectiveness and the predictive ability of the model. This study demonstrates the potential of QSAR modeling in accelerating drug discovery, offering a promising avenue for developing novel therapeutics targeting SmTGR to improve schistosomiasis treatment.

Computational Analysis using Multi-ligand Simultaneous Docking of Withaferin A and Garcinol Reveals Enhanced BCL-2 and AKT-1 Inhibition

P. Biswas, D. Mathur, J. Dinesh, H.K. Dinesh, B.M.A. Desai · ICE 2025 · 2025

AKT-1BCL-2Multi-ligand simultaneous dockingWithaferin A

Uses simultaneous multi-ligand docking to show that combining two natural compounds, Withaferin A and Garcinol, produces stronger inhibition of the cancer-associated proteins BCL-2 and AKT-1 than either compound alone - evidence for a synergistic drug-combination strategy.

Key Finding: Withaferin A + Garcinol MLSD achieved an AKT-1 binding affinity of −13.74 ± 0.08 kcal/mol - nearly double the commercial inhibitor melatonin (−7.24 kcal/mol).

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Developing an effective medicine to combat cancer and elusive stem cells is crucial in the current scenario. Withaferin A and Garcinol, important phytoconstituents of Withania somnifera (Ashwagandha) and Garcinia indica (Kokum) respectively, known for their therapeutic efficiency, have been used for several decades for treating various disorders because of their anti-cancerous, anti-inflammatory and anti-invasive properties. This study investigates the potential of withaferin A and garcinol in inhibiting BCL-2 and AKT-1, crucial proteins contributing to cancer cell persistence by evading apoptosis, increased cell proliferation, and inflammation. Molecular docking techniques, including single docking and MLSD, were used to understand the binding interaction of the ligands with BCL-2 and AKT-1. MLSD highlighted inter-ligand interactions among withaferin A and garcinol against BCL-2, with a binding affinity of -11.88 ± 0.12 kcal/mol, surpassing the binding affinity of venetoclax (-9.73 ± 0.1 kcal/mol), a commercial inhibitor of BCL-2. For AKT-1, the binding affinity of withaferin A and garcinol (-13.74 ± 0.08 kcal/mol) surpassed the binding affinity of melatonin (-7.24 ± 0.06 kcal/mol), a commercial inhibitor of AKT-1. The MLSD results highlight the combined effects of garcinol and withaferin A, underscoring the importance of considering the interactions of bioactive compounds in the development of new medicines and strategies targeting cancer and elusive stem cells.

In Silico Prediction and Validation of LmGt Inhibitors Using QSAR and Molecular Docking Approaches

P. Biswas, M. Bhatt, B.M.A. Desai · ICE 2025 · 2025

Glucose TransportLmGTmolecular dockingQSARSVM classifier

Combines QSAR modeling with molecular docking to identify and validate candidate inhibitors of the LmGt target, an in silico pipeline for narrowing large compound libraries down to the most promising drug candidates.

Key Finding: QSAR model reached 0.81 classification accuracy, with top LmGT docking affinity of −9.46 kcal/mol.

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Leishmaniasis caused by Leishmania mexicana relies on Leishmania mexicana glucose transporter (LmGT) receptors, which play an important role in glucose and ribose uptake at different stages of the parasite's life cycle. Previous efforts to identify LmGT inhibitors have been primarily based on in vitro screening. However, this conventional method is limited by inefficiency, high cost, and lack of specificity, which leaves a significant gap in the development of targeted therapeutic candidates for LmGT. This study employs computational techniques to address this gap by developing a quantitative structure analysis relationship model, utilizing a support vector machine classifier to identify novel LmGt inhibitors. The QSAR model achieved an accuracy of 0.81 in differentiating active compounds. Molecular docking further validated the identified inhibitors, revealing strong binding affinities with a top score of -9.46. The docking analysis showed that the inhibitors formed multiple hydrogen bonds and occupied the same binding pockets as the Phase 3 drug candidate. The tested inhibitors were derived from natural sources, suggesting reduced side effects and improved biocompatibility. This combined approach demonstrates the power of computational models in accelerating drug discovery, with implications for more efficient and biocompatible therapies against Leishmania mexicana.

Prediction of Novel CXCR7 Inhibitors Using QSAR Modeling and Validation via Molecular Docking

B.M.A. Desai, M. Sudha, S. Ghosh, P. Biswas · InCoWoCo 2024 · 2024

cancer inhibitorsCXCR7extra trees classifierQSAR

Applies QSAR modeling to predict novel inhibitors of CXCR7 - a chemokine receptor linked to cancer progression - and validates the top candidates using molecular docking against the receptor structure.

Key Finding: Extra Trees QSAR model hit 0.85 accuracy, identifying CXCR7 inhibitors with a top docking score of −12.24 ± 0.49 kcal/mol.

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CXCR7, a G-protein-coupled chemokine receptor, has recently emerged as a key player in cancer progression, particularly in driving angiogenesis and metastasis. Despite its significance, currently few effective inhibitors exist for targeting this receptor. This study aimed to address this gap by developing a QSAR model to predict potential CXCR7 inhibitors, followed by validation through molecular docking. Using the Extra Trees classifier for QSAR modeling and employing a combination of physicochemical descriptors and molecular fingerprints, compounds were classified as active or inactive with a high accuracy of 0.85. The model could efficiently screen a large dataset, identifying several promising CXCR7 inhibitors. The predicted inhibitors were further validated through molecular docking studies, revealing strong binding affinities, with the best docking score of -12.24 ± 0.49 kcal/mol. Visualization of the docked structures in both 2D and 3D confirmed the interactions between the inhibitors and the CXCR7 receptor, reinforcing their potential efficacy.

Predicting Endocrine Disruptors: A Deep Learning QSAR Model for Estrogen Receptor Activity

B.M.A. Desai, S. Murthy, B. Sridhar, B.M. Anirudh, V. Humtsoe, P. Biswas · IEEE B-HTC 2026 · 2026

Computational toxicologyDeep learningEDCsEstrogen receptorQSAR modeling

Develops a deep learning QSAR model that screens chemical compounds for estrogen receptor activity, flagging potential endocrine-disrupting chemicals earlier and more efficiently than traditional lab-based screening.

Key Finding: Deep learning QSAR model achieved 91.30% test accuracy (ROC-AUC 0.81) predicting estrogen receptor-binding endocrine disruptors.

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Endocrine-disrupting chemicals (EDCs) are compounds that can interfere with hormones and their receptors, affecting growth, reproduction, and other vital functions in humans and wildlife. Since laboratory tests are slow and costly, we created a computational screening method to predict which chemicals are likely to bind the estrogen receptor (ER), a key protein that responds to the hormone estrogen. We used a dataset of 224 compounds described by 2,944 molecular descriptors and fingerprints. These features were fed into a deep neural network (DNN) that included dropout and batch normalization to reduce overfitting and improve training stability. This QSAR model achieved 96.65% accuracy on training data and 91.30% on test data. For the active (ER-binding) class, the model produced a precision of 0.82, a recall of 0.88, and an ROC-AUC of 0.81. To validate predicted active structures, we performed molecular docking using the estrogen receptor structure (PDB ID: 5TOA). Several compounds predicted as active showed docking poses and interactions similar to Estradiol (the natural ligand), including expected hydrogen bonds and hydrophobic contacts. In short, this DNN-based QSAR plus docking workflow provides a fast, cost-effective way to detect chemicals that may act as EDCs by targeting the ER, supporting prioritized laboratory testing and improved environmental and biodiversity risk assessment.

Multi-Ligand Simultaneous Docking Analysis of Moringa Oleifera Phytochemicals Reveals Enhanced BCL-2 Inhibition via Synergistic Action

A. Saha, B.M.A. Desai, P. Biswas · IBIOMED 2024 · 2024

BCL-2Moringa oleiferaMulti-ligand simultaneous dockingSynergistic effect

Screens phytochemicals from Moringa oleifera using simultaneous multi-ligand docking and finds that several act synergistically to inhibit the cancer protein BCL-2 more effectively than single compounds - supporting plant-derived combination therapy.

Key Finding: Multi-ligand simultaneous docking of Moringa oleifera phytochemicals reached −14.96 kcal/mol against BCL-2, surpassing the commercial inhibitor venetoclax.

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Moringa oleifera, known for its medicinal properties, contains bioactive compounds such as polyphenols and flavonoids with diverse therapeutic potentials, including anti-cancer effects. This study investigates the efficacy of M. oleifera leaf phytochemicals in inhibiting BCL-2, a critical protein involved in cancer cell survival. For the first time, multi-ligand simultaneous docking (MLSD) has been employed to understand the anti-cancer properties of M. oleifera leaf extract. Molecular docking techniques, including single-ligand and MLSD, were used to assess binding interactions with BCL-2. Single-ligand docking revealed strong binding affinities for compounds such as niazinin, alpha carotene, hesperetin, apigenin, niaziminin B, and niazimicin A, with some compounds even surpassing Venetoclax, a commercial BCL-2 inhibitor. MLSD highlighted inter-ligand interactions among apigenin, hesperetin, and niazimicin A, exhibiting a binding affinity of -14.96 kcal/mol, indicating a synergistic effect. These results shed light on the potential synergistic effects of phytochemicals when using multi-ligand simultaneous docking, underscoring the importance of considering compound interactions in the development of therapeutic strategies.

Multi-ligand simultaneous docking of Carica papaya leaf phytochemicals, Carpaine and Rutin reveal multi-mechanism inhibition of cancer proteins, BCL-2 and WWP1

M. Sudha, A. Saha, B.M.A. Desai, A.R. Mhashal, P. Biswas · Phytomedicine Plus · 2025

Additive effectAllosterismCarica papayaMulti-ligand simultaneous dockingSynergism

Shows that two compounds from papaya leaf, Carpaine and Rutin, jointly inhibit two different cancer-related proteins (BCL-2 and WWP1) through distinct mechanisms - evidence for a multi-target, plant-derived anti-cancer strategy.

Key Finding: Carpaine + Rutin MLSD raised WWP1 binding affinity to −15.59 ± 0.39 kcal/mol, a synergistic effect further enhanced when combined with bortezomib.

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Cancer remains a major global health concern due to chemotherapy resistance and toxicity from high-dose treatments. To overcome these challenges, new therapeutic strategies targeting key proteins in cancer progression are essential. This study evaluates two phytochemicals, Carpaine (Car) and Rutin (Rut), from Carica papaya leaves, for their potential in enhancing cancer therapy by targeting B-cell lymphoma 2 (BCL-2) and WW domain-containing protein 1 (WWP1) proteins. We assessed their additive, allosteric, and synergistic effects using molecular docking, multi-ligand simultaneous docking (MLSD), molecular dynamics (MD) simulations, and MMPBSA analysis. Car and Rut showed an additive effect on BCL-2 by binding at distinct regions within the same pocket. MLSD revealed an improved binding affinity of -13.13 ± 0.08 kcal/mol over individual ligands or the commercial inhibitor Venetoclax. For WWP1, Car bound near the H-site and Rut near the Le-site, exhibiting an allosteric effect that increased Car's binding affinity in MLSD to -15.59 ± 0.39 kcal/mol. Furthermore, Rut combined with bortezomib demonstrated a synergistic interaction with WWP1, suggesting a more stable complex through synergy. These results suggest Car and Rut, particularly in combination with bortezomib, as promising candidates against cancer-related proteins BCL-2 and WWP1. Further experimental validation is warranted to explore their therapeutic potential.

Biosensing & Diagnostics / Biomedical Devices

Portable devices and functional nanomaterials for real-time diagnostics and treatment - from wound-healing delivery systems to photoacoustic cancer imaging and quantum-dot-based biosensing.

What is the Fiber Gun device?

Fiber Gun is a handheld electrospinning device we developed that deposits biocompatible nanofibers (averaging 100–151 nm in diameter) directly onto a wound in situ, replacing bulky lab-scale electrospinning setups with a single ergonomic unit. Powered by a 12 V battery, it sustains over 10 hours of continuous operation, enabling point-of-care wound treatment outside a lab (Desai et al., IEEE Transactions on Biomedical Engineering, 2026).

Why use quantum dots for biomedical imaging instead of conventional dyes?

Quantum dots offer tunable, size-dependent emission spectra and much higher photostability and quantum yield than organic fluorescent dyes, which is why our reviews cover them for bioimaging, biosensing, and drug delivery (Biswas et al., J. Biol. Regul. Homeost. Agents, 2024). Their clinical adoption still depends on mitigating heavy-metal and reactive-oxygen-species toxicity through surface modification and coating strategies (Sridhar et al., Lecture Notes in Nanoscale Science and Technology, 2026).

How does photoacoustic imaging improve on mammography for breast cancer diagnosis?

Mammography loses sensitivity in dense breast tissue, whereas photoacoustic imaging (PAI) combines optical and ultrasound signals to visualize tumor vascularization, blood oxygenation, and molecular markers in real time - enabling both earlier detection and treatment monitoring, as summarized in our review of PAI techniques (Biswas et al., Lecture Notes in Nanoscale Science and Technology, 2025).

Multi-Task Bacterial Colony Detection and Classification Using YOLOv8 with Edge Optimization for Resource-Constrained Deployment

B.M.A. Desai, R. Rajesh, S. Murthy, P. Biswas, R. Vaithiyanathan · 10th ICCSITSS 2026 · 2026 · Accepted; DOI pending (arXiv preprint)

Bacterial Colony DetectionEdge OptimizationModel CompressionONNXResource-Constrained DeploymentYOLOv8

A deep learning pipeline that detects and classifies bacterial colonies from petri dish images and runs on low-cost edge hardware like a Raspberry Pi, aiming to bring automated microbiology screening to resource-limited lab and field settings.

Key Finding: Achieved 98.13% classification accuracy and 98.27% counting accuracy while running on a Raspberry Pi 4B at roughly 6.4 seconds per inference using an optimized ONNX model.

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This work presents an automated system for bacterial colony enumeration and species classification using deep learning. The approach employs YOLOv8 object detection trained on the AGAR dataset (18,000 images), achieving a classification accuracy of 98.13% and a counting accuracy of 98.27% within a 10-colony margin. To enable deployment on resource-limited devices such as the Raspberry Pi 4B, model optimization techniques including pruning and precision reduction were applied. ONNX FP32 and FP16 variants offered the best balance between inference speed (approximately 6.4 seconds) and accuracy, demonstrating the feasibility of edge-deployable, multi-task bacterial colony analysis for resource-constrained laboratory and field settings.

Fiber gun: A Portable Nanofiber Delivery System for Accelerated Wound Healing

B.M.A. Desai, S.A. Nadaf, R.P.R. Shivakumar, P. Biswas · IEEE Transactions on Biomedical Engineering · 2026 · Article in Press

electrospinningMoringa oleiferananofibersportable electrospinningwound healing

Introduces a handheld electrospinning device ("Fiber Gun") that deposits biocompatible nanofibers directly onto a wound in situ, offering a portable, point-of-care approach to accelerating wound healing outside a lab setting.

Key Finding: Fiber Gun produced nanofibers averaging 100–151 nm in diameter while sustaining over 10 hours of continuous handheld operation.

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Wound healing remains a critical global health challenge, particularly among diabetic patients. Conventional dressings primarily function as passive protective barriers and fail to actively stimulate tissue repair. Electrospun nanofibers, owing to their high surface-area-to-volume ratio and extracellular matrix (ECM)-mimicking architecture, have demonstrated significant potential in enhancing cell proliferation and enabling bioactive functionalization. However, conventional electrospinning systems are bulky, expensive, and unsuitable for field deployment. This study presents Fiber Gun, a fully integrated handheld electrospinning device engineered for in-situ wound care applications. The proposed design miniaturizes and embeds the high-voltage power supply, syringe pump, microcontroller-driven stepper motor, and battery into a single ergonomic unit compatible with standard commercial 2 mL syringes. The device operates at high electric field strengths with precisely controlled low flow rates, enabling stable and reproducible nanofiber generation. Scanning Electron Microscopy (SEM) analysis confirmed consistent nanofiber formation with average diameters ranging from 100 to 151 nm. The fabricated nanofiber mats exhibited uniform morphology and improved mechanical integrity as validated by tensile testing. Bioactive patches prepared using Moringa oleifera (MO)-functionalized polyvinyl alcohol (PVA) demonstrated enhanced biochemical activity, confirmed through Fourier Transform Infrared Spectroscopy (FT-IR), Total Phenolic Content (TPC), and Total Flavonoid Content (TFC) analyses. Powered by a 12 V battery, the system provides over 10 hours of continuous operation, ensuring portability and field deployability. By integrating high-voltage electrospinning into a compact, ergonomic handheld platform, this work bridges the gap between laboratory-scale electrospinning and point-of-care wound treatment, advancing the development of accessible and clinically deployable nanofiber-based wound healing technologies.

Current Updates on Photoacoustic-Based Techniques for Breast Cancer Diagnosis

P. Biswas, M. Sudha, K. Agarwal, M. Bhatt, B. Sridhar, B.M.A. Desai · Lecture Notes in Nanoscale Science and Technology · 2025

Breast cancerMammographyPhotoacoustic imagingPhotoacoustic tomography

A review consolidating recent advances in photoacoustic imaging for breast cancer diagnosis, comparing detection techniques and identifying the gaps that limit clinical translation.

Key Finding: Surveys how photoacoustic imaging adds real-time tumor vascularization and oxygenation data beyond what mammography and MRI alone can capture.

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Breast cancer is the most diagnosed cancer worldwide, with rising incidence rates globally. Early detection is essential for improving survival rates, yet conventional imaging methods have limitations. Mammography, the gold standard, struggles with reduced sensitivity in dense breast tissue. Ultrasound aids in distinguishing lesions but is highly operator-dependent, while MRI offers detailed imaging but remains costly and less accessible. These challenges underscore the need for improved imaging technologies. Photoacoustic imaging (PAI) is an emerging, noninvasive modality that integrates optical and ultrasound imaging to provide high-resolution, real-time visualization of breast tissue. Unlike conventional methods, PAI enables the assessment of tumor vascularization, blood oxygenation, and molecular characteristics, enhancing early cancer detection and treatment monitoring. Various PAI techniques, including photoacoustic tomography, photoacoustic microscopy, multispectral PAI, and photoacoustic endoscopy, offer unique advantages in imaging tumor structure and function. Recent advancements, such as molecular contrast agents and multimodal integration with ultrasound and MRI, further enhance PAI's diagnostic accuracy. This chapter explores the principles, techniques, and applications of PAI in breast cancer detection, tumor characterization, and therapy assessment. We also address challenges in clinical translation and future prospects. With continued development, PAI has the potential to revolutionize breast cancer diagnostics and improve patient outcomes.

Quantum Dots as Functional Nanosystems for Enhanced Biomedical Applications

P. Biswas, A. Saha, B. Sridhar, A. Patel, B.M.A. Desai · Journal of Biological Regulators and Homeostatic Agents · 2024

bioimagingbiosensorsdrug deliveryQuantum Dotstoxicity

Reviews how engineered quantum dots function as imaging and sensing platforms in biomedicine, covering their design principles and applications in diagnostics and targeted therapy.

Key Finding: Highlights tunable emission and high quantum yield as the properties positioning quantum dots for bioimaging and targeted drug delivery, despite unresolved bioaccumulation and toxicity concerns.

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Quantum Dots (QDs) have emerged as promising nanomaterials with unique optical and physical properties, making them highly attractive for various applications in biomedicine. This review provides a comprehensive overview of the types, modes of synthesis, characterization, applications, and recent advances of QDs in the field of biomedicine, with a primary focus on bioimaging, drug delivery, and biosensors. The unique properties of QDs, such as tunable emission spectra, long-term photostability, high quantum yield, and targeted drug delivery, hold tremendous promise for advancing diagnostics, therapeutics, and imaging techniques in biomedical research. However, several significant hurdles remain before their full potential in the biomedical field can be realized, such as bioaccumulation, toxicity, and short-term stability. Addressing these hurdles is essential to effectively incorporate QDs into clinical use and enhance their influence on healthcare outcomes. Furthermore, the review conducts a critical analysis of potential QD toxicity and explores recent progress in strategies and methods to mitigate these adverse effects, such as surface modification, surface coatings, and encapsulation. By thoroughly examining current research and recent advancements, this comprehensive review offers invaluable insights into both the future possibilities and the challenges that lie ahead in fully harnessing the potential of QDs in the field of biomedicine.

Biomedical Applications and Toxicity Mitigation of Functional Quantum Dots

B. Sridhar, M. Sudha, S. Ghosh, B.M.A. Desai, P. Biswas · Lecture Notes in Nanoscale Science and Technology · 2026

BiosensingMultimodal imagingQuantum dotsTargeted deliveryToxicity

Surveys strategies for reducing the toxicity of quantum dots used in biomedical devices - surface coatings, dosing, and material substitutions - so their imaging and sensing benefits can be realized safely in clinical use.

Key Finding: Surface modification and coating strategies emerge as the leading path to curbing heavy-metal and ROS-driven toxicity in biomedical quantum dots.

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Quantum dots (QDs) have emerged as versatile and powerful tools in the biomedical field, offering unique optical and electronic properties for a wide range of applications. These nanoscale semiconductor particles exhibit narrow, symmetric emission bands, making them particularly suitable for bioimaging, biosensing, and drug delivery. Their size-tunable fluorescence and high photostability allow for precise detection, tracking, and manipulation at the molecular and cellular levels, which are crucial for advanced biomedical applications. QDs enable high-resolution imaging and multianalyte detection, proving invaluable in cancer detection, infection monitoring, and cellular studies. Despite their significant advantages, integrating QDs into clinical and diagnostic settings raises concerns about their potential toxicity and environmental impact. QDs can induce toxicity at the cellular and organ levels, primarily through the release of heavy metal ions and reactive oxygen species (ROS). This chapter introduces QDs, highlighting how their size-tunable fluorescence and high photostability enhance imaging, drug delivery, and biosensing. This work delves into the synthesis and functionalization of QDs and explores how surface modifications and coating techniques can increase their biocompatibility and reduce their toxicity. By addressing both the biomedical applications and potential risks associated with QDs, this chapter provides a comprehensive overview of the current state of QD technology.

Green Nanotechnology & Sustainable Bio-Processing

High-voltage electric discharge (HVED) and nanoparticle engineering for sustainable extraction of bioactives and next-generation therapeutic formulations.

What is high-voltage electric discharge (HVED) extraction?

HVED is a non-thermal, chemical-free technique that applies high-voltage pulses to rupture plant cell walls and release intracellular proteins. In our peanut meal studies, HVED pretreatment combined with alkaline extraction achieved an 89.86% protein yield - more than 4x higher than alkaline extraction alone (19.86%) - at optimized conditions of 25 kV, 7.5 Ω, and 20 discharges (Biswas et al., ACS Food Science and Technology, 2025).

Why nanonize bioactive compounds instead of using them in bulk form?

Nanonization increases a bioactive compound's surface-area-to-volume ratio, improving its solubility, bioavailability, and pharmacological activity compared to conventional bulk formulations. Our review covers techniques ranging from wet-media milling and electrospinning to supercritical fluid technology, along with the encapsulation strategies used to protect these nanoformulations during delivery (Biswas et al., Discover Materials, 2026).

Green Extraction of Protein from Peanut Meal: Valorization via High-Voltage Electric Discharge

P. Biswas, B. Sridhar, K. Agarwal, S.K. Panigrahi, B.M.A. Desai · ACS Food Science and Technology · 2025

green extraction technologyhigh-voltage electric dischargepeanut mealprotein extraction

Demonstrates that high-voltage electric discharge (HVED) pretreatment improves protein recovery from peanut meal, an agri-residue byproduct, offering a greener alternative to chemical-solvent extraction.

Key Finding: HVED pretreatment lifted peanut-meal protein yield to 89.86% - over 4x the 19.86% achieved by alkaline extraction alone.

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India is the second-largest producer of peanuts, yielding over 10 million metric tonnes annually. Most are processed for oil, generating peanut meal, a protein-rich (40-55 wt%) byproduct. This study evaluates high-voltage electric discharge (HVED) with alkaline extraction (AE) as a sustainable method to enhance protein recovery. HVED uses high-voltage pulses to disrupt cellular structures, aiding protein release. Compared to AE (19.86%), microwave-assisted extraction (MAE, 33.62%), and ultrasound-assisted extraction (UAE, 48.51%), HVED-AE achieved the highest yield (89.86%) with lower energy input, optimized at 25 kV, 7.5 Ω, and 20 discharges. Protein integrity was confirmed by fluorescence spectral analysis. These findings demonstrate HVED-AE as a superior, eco-friendly extraction method supporting a circular economy. This aligns with the UN's Sustainable Development Goals (SDGs), including zero hunger (SDG 2), good health and well-being (SDG 3), industry, innovation, and infrastructure (SDG 9), and responsible consumption and production (SDG 12), promoting scalable plant-based protein recovery from agro-waste.

Enhancing Protein Recovery from Peanut Meal: High-Voltage Electrical Discharge as an Efficient and Green Pretreatment Method

B. Sridhar, P. Biswas, B.M.A. Desai · IBIOMED 2024 · 2024

Alkaline ExtractionHVEDPeanut mealProtein extraction

Optimizes HVED pretreatment parameters to maximize protein yield from peanut meal, laying groundwork for scaling this green-extraction method beyond the lab.

Key Finding: Identified pH 11 and a 1:25 solid-to-solvent ratio as the optimal conditions, with HVED pretreatment outyielding alkaline extraction alone.

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Efficient and sustainable protein extraction from agro-industrial by-products like peanut meal is crucial for maximizing their potential. This study introduces a novel, environmentally friendly technique known as High-Voltage Electrical Discharge (HVED) for protein extraction from peanut meal. Given the increasing demand for sustainable plant-based proteins, and with peanut meal being a significant global resource, green extraction methods are essential to minimize environmental impact. This study marks the first application of HVED for peanut meal protein extraction, offering a better alternative to other conventional methods. This method utilizes high-voltage electrical discharges to disrupt cell structures and liberate proteins without harsh chemicals or high temperatures. HVED pretreatment is followed by alkaline extraction (AE). This study optimizes AE parameters, such as pH and solid-to-solvent ratios, to enhance protein extraction efficiency, and compares the fluorescence properties of proteins extracted via AE only and with HVED pretreatment. Results showed that optimal conditions at pH 11 and a solid-to-solvent ratio of 1:25 produced the best protein extraction, with HVED pretreatment yielding a higher protein concentration than AE. Fluorescence spectroscopy revealed a bathochromic shift in both AE and HVED-treated samples, likely due to the alkaline medium. These findings highlight HVED's potential as an efficient and sustainable pretreatment method for protein extraction, promoting environmentally friendly processes.

Nanonizing bioactives: precision chemistry for next-gen therapeutics

P. Biswas, B.M.A. Desai, S. Ghosh, B. Banerjee, D. Verma, M. Kathirselvam, S. Chauhan, P.K. Gupta · Discover Materials · 2026

Bioactive compoundsDrug deliveryNano-Drug delivery systemsNanonization techniques

A review of nanonization techniques for converting bioactive compounds into nanoscale formulations, examining how precision chemistry improves the solubility, stability, and targeted delivery of next-generation therapeutics.

Key Finding: Positions nanonization as the key lever for boosting bioavailability of bioactive compounds, comparing techniques from wet-media milling to supercritical fluid processing.

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Bioactive compounds have been utilised for their therapeutic effects in various biomedical applications for a long time. The growing global emphasis on health has driven a significant increase in demand for these compounds in recent years. However, using them in the conventional formats does not achieve the required bioavailability for the desired effects. Thus, there is a growing need for nanonizing bioactive compounds, as this significantly increases the surface area-to-volume ratio and enhances their pharmacological activities. This review aims to provide a comprehensive overview of the various techniques that can be used to prepare nanonized formulations of such compounds. This ranges from widely used techniques, such as wet-media milling and electrospinning, to relatively newer techniques, including supercritical fluid technology. Additionally, we have covered the various encapsulation layers that can be employed to protect these nanoformulations and facilitate the delivery of the nanomaterials. Delivery of such bioactive compounds can be achieved through invasive and non-invasive methods. After entering these compounds into the biological system, they are taken up by the cells via active or passive transport. However, despite these advancements, many challenges remain during the preparation of these formulations. During the preparation of nanomaterials, it thus becomes essential to address these challenges and carefully evaluate the different parameters before scaling up the manufacturing process.

Electrical Insulation & Power Systems (Foundational Research)

My doctoral and postdoctoral work at IIT Madras and Khalifa University - condition monitoring, partial discharge diagnostics, and dielectric materials characterization - that established the signal-processing and materials-science foundation for my current biomedical and AI research.

How are partial discharges located inside transformer insulation?

We use UHF signal acquisition combined with Cross Recurrence Plot (CRP) analysis to estimate the time difference of arrival (TDOA) between sensors, which localizes the discharge source non-iteratively and remains accurate even under low signal-to-noise ratio, outperforming standard cross-correlation methods (Desai & Sarathi, IEEE TDEI, 2018).

Do nanofillers actually improve insulation material performance?

Yes - nano-alumina fillers improved corona ageing resistance in silicone rubber composites, though with a marginal reduction in hydrophobicity-recovery rate (Vinod et al., IEEE TDEI, 2019), while nano-montmorillonite clay increased LDPE's corona ageing resistance and storage modulus while reducing loss tangent (Mallayan et al., Micro and Nano Letters, 2019). Both effects trace back to how the fillers shift the material's charge-trap distribution.

Show all 14 papers

Investigation on the electrical, thermal and mechanical properties of silicone rubber nanocomposites

P. Vinod, B.M.A. Desai, R. Sarathi, S. Kornhuber · IEEE Transactions on Dielectrics and Electrical Insulation · 2019

coronaLIBSnano aluminasilicone rubber

Characterizes how nanofiller loading changes the electrical, thermal, and mechanical performance of silicone rubber used in outdoor high-voltage insulation.

Key Finding: Nano-alumina filler improved corona ageing resistance in silicone rubber, though it modestly reduced hydrophobicity-recovery rate.

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Addition of alumina nano particles to silicone rubber (SR) has shown a significant improvement in electrical, mechanical and thermal properties of the SR nanocomposites. Static contact angle and water droplet-initiated corona inception voltage exhibited a marginal change on inclusion of nano alumina into SR matrix. Alumina filler improved the corona ageing resistance of the composites; however, a marginal reduction in the rate of hydrophobicity recovery is observed. Laser induced breakdown spectroscopy proved to be an effective tool to rank the performance of the SR nano composites. Variation of crater depth with energy of laser pulse and number of laser pulses follows the exponential relation. Plasma temperature calculated by optical emission spectroscopy is in line with the amount of damage caused to the surface of the specimen by water droplet-initiated discharge. Dielectric response spectroscopic studies indicate that inclusion of nano fillers has resulted in lower interfacial polarization and lower imaginary permittivity. It is observed through dynamic mechanical analysis that the composites have higher storage modulus and the activation energy compared to base SR.

Identification and localisation of incipient discharges in transformer insulation adopting UHF technique

B.M.A. Desai, R. Sarathi · IEEE Transactions on Dielectrics and Electrical Insulation · 2018

corona dischargecross-recurrence plotlocalizationTDOA

Develops a UHF-based signal processing technique to detect and pinpoint early-stage partial discharges inside transformer insulation before they cause failure - a diagnostic approach later adapted to biomedical signal processing.

Key Finding: Cross Recurrence Plot analysis localized incipient discharge sources accurately even under low signal-to-noise ratio, outperforming cross-correlation.

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Incipient discharges formed in natural ester oil due to corona activity, surface discharges and particle movement were investigated using UHF technique. When the applied voltage magnitude is increased, on the inception of discharges, the peak to peak magnitude of the voltage of the UHF signal formed also increases. After a certain applied voltage magnitude increase, if it is reduced, the magnitude of the UHF signal formed is much higher than the magnitude of the signal formed when the voltage is increased. This phenomenon is observed with all three types of discharges. Cross Recurrence plot (CRP) can be effectively used to determine the Time Difference Of Arrival (TDOA) of UHF signals. Self-similarity Recurrence Quantification Analysis (RQA) parameter is found to be a more suitable technique to estimate the TDOA of UHF signals. CRP method is used to estimate TDOA correctly, even with low signal to noise ratio, and it is found to be superior to the Cross-correlation technique in estimating the TDOA. Estimated TDOA of UHF signals are validated and the incipient discharge source is localized by adopting a non-iterative technique.

Understanding the performance of corona aged epoxy nano micro composites

B.M.A. Desai, P. Mishra, N.J. Vasa, R. Sarathi, T. Imai · Micro and Nano Letters · 2018

Corona ageingEpoxy nanocompositesLaser-induced breakdown spectroscopyWollastonite

Compares how different fillers in epoxy nanocomposites resist corona-discharge ageing, using laser-induced breakdown spectroscopy to characterize surface degradation.

Key Finding: Wollastonite-filled epoxy composite resisted laser abrasion where nano-micro silica-filled composites did not, indicating superior corona-discharge resistance.

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The research examines how corona aging affects epoxy nanocomposite surfaces, particularly measuring contact angle changes. Composites containing Wollastonite filler demonstrated superior resistance to corona degradation compared to those with nano-micro silica fillers. The study employed laser-induced breakdown spectroscopy (LIBS) to characterize material aging conditions by analyzing plasma temperature and threshold fluence. Epoxy composite with Wollastonite as filler was not affected by laser abrasion and demonstrated enhanced discharge-resistant properties.

Understanding the Water Droplet Initiated Discharges on Silicone Rubber Adopting Optical Emission and Laser Induced Breakdown Spectroscopy

B.M. Ashwin Desai, R. Sarathi, S. Kornhuber · INAE Letters · 2019

Laser Induced Breakdown SpectroscopyOptical Emission SpectroscopySilicone RubberWater Droplet Discharges

Uses two complementary spectroscopic techniques, optical emission and laser induced breakdown spectroscopy, to characterize water-droplet-triggered discharge activity on silicone rubber insulation surfaces.

Key Finding: Combined OES and LIBS analysis characterized discharge activity and surface degradation from water-droplet corona, informing long-term outdoor insulation performance under wet conditions.

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Water droplet initiated discharges on silicone rubber insulation surfaces were investigated using optical emission spectroscopy (OES) and laser induced breakdown spectroscopy (LIBS). These complementary spectroscopic techniques were used to characterize the discharge activity and surface degradation caused by water droplet corona on silicone rubber, contributing to understanding of long-term outdoor insulation performance under wet conditions.

Understanding the performance of gamma-ray-irradiated epoxy nanocomposites

P. Mishra, B.M.A. Desai, N.J. Vasa, R. Sarathi, T. Imai · Micro and Nano Letters · 2019

gamma irradiationepoxy nanocompositesdielectric relaxation spectroscopy

Studies how gamma-ray exposure alters the structure and performance of epoxy nanocomposites, relevant to insulation used in radiation-exposed environments.

Key Finding: Gamma-ray irradiation sharply reduced surface potential decay time and increased charge mobility in epoxy nanocomposites.

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Epoxy nanocomposites being used in the high-energy radiation zones as an insulant may undergo changes in their dielectric properties during service. In the present study, the performance of base epoxy resin (S1) is compared with epoxy resin with ion trapping particle (Sample S2) and epoxy resin with nanotitania (Sample S3) particle. The influence of gamma irradiation on nanocomposites was analysed. Corona inception voltage due to water droplet initiated discharge and contact angle reduces post-gamma-ray irradiation. Surface potential decay time constant reduced drastically for gamma-ray-irradiated specimens. Trap distribution characterisation indicated that charge mobility increases after irradiation. The surface roughness of the sample increases with the irradiation dosage. Dielectric relaxation spectroscopy shows that permittivity reduces and loss tangent increases with the gamma-irradiated specimens. Water diffusion rate increases for the gamma-ray-irradiated specimen. No change in elemental composition, measured using laser-induced breakdown spectroscopy, of test specimens was observed. The hardness of the material and plasma temperature formed during laser shine decreases with gamma-ray irradiation intensity for Sample S1, whereas samples S2 and S3 showed only marginal variation. The performance of Sample S2 is found to be better than Samples S1 and S3.

Investigation on the thermal properties, space charge and charge trap characteristics of silicone rubber nano‑micro composites

P. Vinod, B.M.A. Desai, R. Sarathi, S. Kornhuber · Electrical Engineering · 2021

AluminaCoronaSilicone rubberSpace charge

Examines how mixed nano- and micro-scale fillers affect charge trapping and thermal behavior in silicone rubber composites used for insulation.

Key Finding: ATH and nano-alumina fillers shifted the charge-trap distribution and improved thermal stability of silicone rubber composites.

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The micro-aluminium trihydrate (ATH) and nano-alumina fillers in the silicone rubber (SR) significantly improve the electrical, thermal and mechanical properties. ATH fillers improved the resistance to the corona ageing and water droplet-initiated erosion. Scanning electron microscopy (SEM) analysis was carried out to understand degradation condition caused due to corona ageing and damage caused due to water droplet-initiated discharges. The inclusion of these fillers significantly altered the surface and bulk charge distribution characteristics of the polymer. A right shift is observed in the trap distribution characteristics. The reduced electric field threshold limit for space charge formation is observed with composites, due to increment in impurities/agglomerations with respect to increment in filler concentration. Performance of composites subjected to polarity reversal is improved on inclusion of nano-filler in addition to micro-filler. The inclusion of fillers enhanced the thermal conductivity and improved significantly the thermal stability of the SR composite.

Partial Discharge Source Classification using Time-Frequency Transformation

B.M.A. Desai, R. Sarathi, J. Xavier, A. Senugupta · ICIIS 2018 · 2018

Classificationpartial dischargesSVMTime Frequency transformation

Applies time-frequency signal transformation to automatically classify different sources of partial discharge - an early example of the signal-processing techniques now common in biomedical diagnostics.

Key Finding: A quadratic SVM classifier successfully distinguished partial-discharge sources from time-frequency transformed UHF signals under simulated field conditions.

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UHF signals generated by partial discharges due to corona activity, surface discharge and particle movement in transformer oil were acquired and used to develop a classification model. Time-Frequency transformation of the UHF signal emitted by the partial discharge source was used for classification of the discharges using a quadratic support vector machine (SVM) learning tool. The method was validated by simulating the field condition, by studying the classification model in an oil filled closed tank along with the pressboard along the path of the UHF signal, as observed in a real system.

Investigation into Variation of Resistivity and Permittivity of Aqueous Solutions and Soils with Frequency and Current Density

A.D.B. Manjunath, F. Khan, N. Noyanbayev, N. Harid, H. Griffiths, R.P. Nogueira, N.T.C. De Oliveira, M. Haddad, S. Ramanujam · IEEE Transactions on Electromagnetic Compatibility · 2022

GroundingPermittivityResistivitySoil

Measures how the electrical resistivity and permittivity of soils and aqueous solutions vary with frequency and current density, informing more accurate grounding-system design.

Key Finding: Measured soil/electrolyte impedance across 1 Hz–10 MHz and 1–35 mA/m² current density, showing that electrode-electrolyte interface effects have caused prior studies to overestimate resistivity and permittivity.

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Soil parameter characterization and the variation of permittivity and resistivity with frequency (dispersion) and current density have been the subject of many experimental studies but significant differences in measured values are found in the literature due to different testing approaches, apparatus, and test sample composition. This article first presents a comprehensive review of this previous body of work. Then, new experiments on soils and electrolytes with test frequencies in the range 1 Hz to 10 MHz and with current densities from 1 to 35 mA/m2 are described. Such results help clarify the effects of frequency, soil moisture, electrolyte concentration, and electrode material on the measured test medium parameters. The contribution of the electrode-electrolyte interface (EEI) and the influence of current density are particularly highlighted. These findings indicate that some previous measurements may have overestimated the measured values of resistivity and permittivity due to the EEI effect. Finally, the test results are compared with soil parameter equations from CIGRE TB781.

Understanding of Incipient discharges in Transformer Insulation by reconstruction of Digital Twins for the discharges using Generative Adversarial Networks

G.D.P. Mahidhar, B.A. Kumar, R. Sarathi, N. Taylor, H. Edin, B.M.A. Desai · EIC 2021 · 2021

Generative Adversarial NetworksPartial DischargeTransformer insulationUHF technique

Uses generative adversarial networks (GANs) to reconstruct digital twins of partial-discharge signals, an early application of generative deep learning to insulation diagnostics.

Key Finding: A DCGAN reconstructed high-fidelity UHF partial-discharge signals, recovering realistic time-frequency characteristics from known defect models.

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Partial discharge (PD) monitoring is one of the diagnostic techniques adopted for identifying the variety of defects in transformer insulation. Ultra high frequency (UHF) technique is gaining importance in PD monitoring applications of transformers due to various advantages. Different types of incipient discharges arise from defects in transformer insulation that need to be identified. In an actual test site there can be noise that can hinder data acquisition, and defect identification can become difficult. By using artificially reconstructed signals of known practically occurring defect models, the loss in data can be overcome. In the present study, Deep Convolutional Generative Adversarial Networks (DCGAN) technique is adopted to reconstruct the UHF partial discharge signals with high fidelity. Time-Frequency characteristics of the signals were used to build the DCGAN network and the reconstructed UHF signals are evaluated by studying the frequency characteristics of the generated signal.

Understanding the electrical, thermal and mechanical properties of LDPE-clay nanocomposites

S. Mallayan, R.R. Prabhu, B.M.A. Desai, R. Velmurugan, R. Sarathi, B.N. Rao · Micro and Nano Letters · 2019

LDPE-clay nanocompositescorona inception voltagethermomechanical properties

Characterizes LDPE-clay nanocomposite films to understand how clay nanofillers alter electrical, thermal, and mechanical properties for insulation applications.

Key Finding: Nano-montmorillonite clay inclusion increased LDPE's corona ageing resistance and storage modulus while reducing loss tangent.

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The performance of low-density polyethylene (LDPE) clay nanocomposites was analysed. The inclusion of nano montmorillonite (MMT) clay in LDPE material has significantly increased the contact angle, corona ageing resistance, water droplet initiated corona inception voltage and surface discharge inception voltage of the composites. The surface charge decay rate of the samples significantly reduced on the inclusion of clay indicating modified trap distribution characteristics due to the inclusion of the filler. Dynamical mechanical analysis indicates increased storage modulus and reduced loss tangent due to nanofillers inclusion. Laser-induced breakdown spectroscopy indicates that on inclusion of nanofillers the plasma temperature increases and crater depth decreases. In particular, increased discharge resistance, improved thermomechanical properties are observed with LDPE-MMT clay composites compared to pure LDPE.

Equivalent Circuit Models for Soils and Aqueous Solutions Under 2-Terminal Test Configuration

A.D.B. Manjunath, N. Harid, H. Griffiths, R.P. Nogueira, N. Noyanbayev, A. Haddad, S. Ramanujam · IEEE Transactions on Electromagnetic Compatibility · 2023

Circuit modelelectrode-electrolyte interface (EEI)impedancesoil conduction

Proposes equivalent circuit models to represent the impedance behavior of soils and aqueous solutions measured in a two-terminal configuration, simplifying grounding system analysis.

Key Finding: A constant-phase-element circuit model accurately reproduced electrode-electrolyte interface behavior across 10 mHz–10 MHz for both soils and electrolytes.

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Numerous circuit models have been proposed to represent the electrode-electrolyte interface (EEI) impedance and bulk medium impedance of conducting media. Following a review, two suitable models are constructed to represent the behavior of conduction in electrolytes and soils, respectively. Both models incorporate a constant phase element in parallel with an apparent Faradaic resistance, which is found to reproduce the EEI behavior accurately. For the electrolyte model, a single parallel R-C branch is added to represent the impedance of the bulk medium, whereas for the soil model, an equivalent ladder network of R-C branches is found to be suitable. Experimentally obtained electrolyte and soil impedance data based on 2-terminal impedance spectroscopy over a frequency range of 10 mHz to 10 MHz with variable current density are compared with values obtained from the models and where model parameters are determined by a curve fitting routine. The effects of electrolyte concentration, soil moisture, and electrode material are analyzed, and the models help to illustrate clearly how the EEI effect dominates at low frequencies while the intrinsic characteristics of the test medium prevails at high frequencies. The models are extended to account for soil-electrolyte impedance dependence on current density, which is most evident at low frequencies.

Performance analysis of epoxy nanocomposites due to water droplet-initiated discharges under AC and DC voltages and localisation of discharges

P. Mishra, B.M.A. Desai, R. Sarathi, T. Imai · IET Science, Measurement & Technology · 2019

Corona inception voltageepoxy nanocompositesTDOA

Investigates how water droplets on epoxy nanocomposite surfaces trigger electrical discharges under AC and DC stress, and localizes the discharge sites for diagnostic purposes.

Key Finding: Corona inception voltage from water-droplet discharges was highest under negative DC and lowest under AC excitation.

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Corona inception voltage (CIV) due to water droplet sitting over the surface of epoxy nanocomposite material depends on supply voltage frequency, the conductivity of water droplet and the contact angle of the test specimens. The contact angle of the specimen and CIV due to water droplet has a direct correlation. It is realised that the CIV is high under negative DC and the least under AC voltages. Surface charge accumulation studies indicate that the accumulated charge and its decay time constant reduces in the damage-caused zone due to corona activity. The ultra-high frequency (UHF) signal generated due to water droplet-initiated corona activity has frequency content in the range of 0.8-1 GHz. The localisation of incipient discharges is demonstrated by using the non-iterative technique and the cross recurrence plot (CRP) technique is used to estimate the time difference of arrival (TDOA) of UHF signals generated due to water droplet-initiated discharge. Laser-induced breakdown spectroscopy (LIBS) depicts the elemental composition and reveals the difference in plasma temperature and threshold fluence between all the test specimens.

Application of the Impulse Response of Transformer Winding for Detection of Internal Turn-to-Turn Short Circuits

M. Shadid, N. Harid, B. Barkat, A. Manjunath · UPEC 2022 · 2022

fault diagnosisFrequency response analysisimpulse methodTransformer

Uses transformer winding impulse-response signatures to detect internal turn-to-turn short circuits before they escalate into failures.

Key Finding: Impulse-response testing matched the diagnostic sensitivity of the standard swept-frequency method for turn-to-turn short circuits, in less test time.

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Several techniques are currently used to monitor internal defects in power transformers. These are very useful for reducing failure rates and extending the service life of transformers. One of the most sensitive techniques is the frequency response analysis method that injects a swept frequency ac signal into the transformer winding and analyses differences between the measured output signal and a benchmark reference signal. This paper applies the impulse voltage method for the diagnosis of turn-to-turn short circuit faults inside a transformer winding. The input signals are a set of impulse voltages of different shapes instead of the standard ac signals of variable frequency. The merits of this method compared with the standard swept frequency method are a shorter time for testing and for signal analysis. The output results are processed to produce a frequency response plot of the winding. Measurement results on a small test transformer show that the plots are closely similar to those obtained using the swept frequency method. In this initial study, impulse voltages are used to emulate the naturally occurring transients in power systems such as switching events and tap changer operations. The sensitivity of the method is verified by applying statistical techniques to interpret the measured frequency response in different frequency bands.

Dendrogram based Clustering and Separation of Individual and Simultaneously Active Incipient Discharges in Transformer Insulation

N.K. Haneefa, B.M. Ashwin Desai, R. Sarathi, M. Rathinam · SPCOM 2020 · 2020

dendrogramPartial dischargesunsupervised clusteringwavelets

Uses dendrogram-based clustering to separate overlapping partial-discharge signals when multiple discharge sources are simultaneously active - improving diagnostic accuracy in noisy conditions.

Key Finding: An unsupervised dendrogram-clustering approach successfully separated simultaneously active partial-discharge sources using cosine similarity of wavelet-based features.

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Partial discharges in transformer insulation are of major concern to utilities which cause the catastrophic failure of insulation. One of the major challenges is the identification of discharges from multiple sources when it occurs concurrently. Hence it is imperative to devise methods for identifying and separating those signals for corrective measures. In this study, an unsupervised learning approach is proposed for clustering of individual partial discharge signals and then using that information for separating the multi-source signals. Our clustering approach works by constructing a dendrogram by measuring the cosine similarity between the feature vectors and then computing a threshold, to group the individual source signals into different clusters. The feature vectors include the relative energies from the wavelet packet decomposed tree and the Higuchi fractal dimension of the wavelet coefficients at the terminal nodes. The generated clusters are trained using a classifier model to separate the individual and multi-source signals. The proposed approach is a simple and robust technique for individual cluster groupings and individual to multiclass separations and could be used for multiclass cluster groupings.

Impedance Spectroscopy of Aqueous Solutions and Soils Using the Impulse Method

N. Noyanbayev, A.D.B. Manjunath, N. Harid · UPEC 2024 · 2024

impedance spectroscopyimpulse methodpermittivityresistivity

Applies an impulse-based impedance spectroscopy method to characterize the frequency-dependent electrical behavior of soils and aqueous solutions.

Key Finding: The impulse method matched frequency-domain impedance spectroscopy accuracy while cutting measurement time and equipment cost.

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This study investigates the variation of soil resistivity and permittivity using the impulse method impedance spectroscopy. Experiments were conducted with an aqueous solution of Na2SO4 at varying concentrations and sand with different moisture contents. Measurements were taken in the frequency range of 1 Hz to 10 MHz using multiple double exponential waves. The results derived from FFT analysis of time-domain data were compared with frequency-domain impedance spectroscopy (FDIS), highlighting the accuracy and efficiency of the impulse method in determining soil electrical parameters. The study demonstrates that the impulse method can provide reliable results with significantly reduced measurement time and equipment costs compared to traditional FDIS methods. Additionally, the impulse method's applicability in field conditions makes it a practical alternative for various soil impedance measurements, offering insights into soil behavior under different environmental conditions.

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