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648 results on '"Kumar, Harendra"'

29. A comprehensive approach towards detection of sub-surface microscopic damage in low alloy ferritic steels using ultrasonic technique

Author

Kumar, Harendra, Nadendla, H., and Gan, T.-H

Subjects
Non-destructive evaluation, microstructural degradation in steel, ultrasonic NDE technique, plant life extension, fitness for service assessment, risk-based inspection, heat treatment quality, irradiation damage assessment, steel components, nuclear plant, hydrogen damage
Abstract

Service induced micro-damage poses an indiscriminate threat to the integrity of piping and pressure vessels used in various energy sectors. Type IV creep and high-temperature hydrogen attack (HTHA) are two typical examples of such high-temperature damage mechanisms known to accumulate in the material's volume prior to the formation of macro cracks. This accumulation of microscopic damage effectively reduces the stress bearing cross-section of the material and may result in the sudden failure of the component. Therefore, the industry is increasingly interested in non-destructively detecting such degradation at an early stage and subsequently monitoring its progression during service. The ultrasonic testing was identified as a potential, viable, field-deployable method for providing information on the presence of early-stage localised damage in the material's volume. The availability of specimens containing representative damage was considered crucial for developing and validating the ultrasonic technique. This research is explicitly concerned with the generation of samples containing Type IV creep and the development of an ultrasonic technique for the earliest detection of Type IV creep while in the secondary stage of progression. Cross weld tensile specimens machined from electron beam (EB) and arc welded ASTM Grade 91 steel pipe section were subjected to uniaxial creep test. Creep test temperature and stress were optimised within the industrially relevant range to induce localised creep damage under accelerated conditions. Specimens representing a spectrum of damage from early secondary-stage to late tertiary-stage creep were successfully generated for ultrasonic technique capability assessment and further development. It was found that under the uniaxial creep test, the localised creep initiates and develops into a crack underneath the surface. In most creep-tested cross-weld samples; the Type IV creep progresses faster in the heat-affected zone (HAZ), corresponding to a larger bevel angle. In general, despite a wider HAZ, the electron beam welded specimen's creep life was longer compared to the arc welded sample. Several ultrasonic techniques utilising advances in electronics and signal processing capabilities were examined to bring down the detection threshold. The experimental investigation performed on industrially relevant specimen containing verifiable representative damage reveals the inadequacy of state-of-the-art full matrix capture (FMC) / total focusing method (TFM) technique for Type IV creep detection at an early stage. However, at the stage when damage can produce weak reflections, FMC/TFM may offer good spatial resolution and improved SNR due to synthetic focusing in the region of interest. Furthermore, TFM could be advantageous for characterising the advanced stage damage when it starts to orient. A focused ultrasonic testing technique utilising custom-designed single crystal probe applied with optimised parameters enabled improved detection of Type IV creep at the mid secondary stage of progression. This work establishes the significance of focusing ultrasound energy during the forward propagation into the region of interest to detect microscopic damage in ferritic-martensitic steels. The performance comparison with the FMC/TFM technique available on portable commercial equipment, supports the fundamental, that detection of microscopic damage, scattering ultrasound, is primarily governed by the intensity of ultrasound energy transmitted into the region of interest. Once the region is insonified appropriately, any limitation on detecting such scatterers largely relates to the material and receiver characteristics.

Published
2022

43. Soft Tissue Sarcoma in Sub‐Saharan Africa: Surgical Management Outcomes, Gaps, and Future Prospects: A Narrative Review.

Author

Adebusoye, Favour Tope, Roy, Sakshi, Bharadwaj, Hareesha Rishab, Ali, Syed Hasham, Awuah, Wireko Andrew, Ferreira, Tomas, Tan, Joecelyn Kirani, Aderinto, Nicholas, Azeem, Saleha, Salako, Paul Olutosin, Tenkorang, Pearl Ohenewaa, Kumar, Harendra, and Abdul‐Rahman, Toufik

Subjects
CAREER development, PUBLIC health infrastructure, SARCOMA, QUALITY of life, SURGICAL complications
Abstract

Background and Aims: The diagnosis and management of soft tissue sarcoma (STS) in sub‐Saharan Africa (SSA) present significant challenges. Positive outcomes in STS treatment include achieving negative margins, improved quality of life, and reduced recurrence rates, while negative outcomes involve incomplete resection, local recurrence, and surgical complications. This review aims to examine the current state of STS management in SSA, identify key challenges, and propose potential solutions to improve patient outcomes. Methods: A comprehensive review of the literature using PubMed/MEDLINE, Google Scholar, and Scopus, focusing on English‐language studies examining the management of STS in SSA. Inclusion criteria centered on studies reporting on surgical interventions, outcomes, and healthcare challenges in the region. Articles lacking sufficient data, non‐English sources, conference abstracts, and duplicates were excluded. Results: Findings highlight several obstacles in the management of STS in SSA, including limited multidisciplinary teams, inadequate healthcare infrastructure, financial constraints, and lack of standardized treatment protocols. Key themes such as diagnostic capacity and resource allocation were identified as significant barriers. Conclusion: Improving STS outcomes in SSA requires investment in healthcare infrastructure, professional development, enhanced funding, and collaborative research. Addressing these gaps is crucial to achieving better surgical management and improving survival rates for patients with STS in SSA. [ABSTRACT FROM AUTHOR]

Published
2024
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44. Thermoelastic damping analysis in micro-beam resonators in the frame of modified couple stress and Moore–Gibson–Thompson (MGT) thermoelasticity theories.

Author

Singh, Bhagwan, Kumar, Harendra, and Mukhopadhyay, Santwana

Subjects
*STRAINS & stresses (Mechanics), *QUALITY factor, *HEAT conduction, *ENERGY dissipation, *RESONATORS, *THERMOELASTICITY
Abstract

The thermoelastic coupling between strain and temperature fields arising out from temperature gradient, while bending of an oscillating structure, leads to irreversible heat conduction, which causes energy dissipation in such vibrating systems. The estimation of thermoelastic damping (TED) in micro- and nano-mechanical resonators is a significant aspect of acquiring a high quality factor (Q-factor). Yang et al. [Couple stress based strain gradient theory for elasticity. Int J Solids Struct. 2002;39(10):2731–2743.] developed the modified couple stress theory (MCST) that involves only one material length scale parameter. The present work attempts to investigate TED in micro/nano-beam resonators utilizing MCST and the recently proposed Moore–Gibson–Thompson (MGT) generalized thermoelasticity theory. Adopting the frequency approach method, we derive the size-dependent expression of the inverse quality factor for evaluating TED in rectangular micro/nano-beam resonators. Furthermore, the impact of the material length scale parameter on TED associated with MCST for silicon micro-beam resonator is investigated in detail by comparing the present results with those predicted by classical continuum theory (CCT). The obtained results are also compared with the existing results for the Lord–Shulman (LS) and Green–Naghdi (GN-III) thermoelasticity theories. Moreover, the effects of other important parameters like beam thickness, beam length, aspect ratio, phase-lag on TED in the present context are highlighted. [ABSTRACT FROM AUTHOR]

Published
2024
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49. Pharmacogenomics & Personalized Medication Management in Geriatric Psychiatry: A Systematic Review

Author

Poudel, Sujan, primary, Greca, Elona, additional, Panta, Nisha, additional, Choudhari, Jinal, additional, Kumar, Harendra, additional, Mahawa, Rukam, additional, Sharma, Ashutosh, additional, Munir, Amna Bint I, additional, Guntipalli, Prathima, additional, Dey, Rohit Chandra, additional, Dixit, Aishwar, additional, Ahmed, Sultan S., additional, Echols, Martha, additional, and Ferrer, Gerardo F., additional

Published
2024
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50. Study and Design of Route Repairing Mechanism in MANET

Author

Kumar, Harendra, Malakar, Madhuri, Debnath, Sourabh, Rafi, Mudassir, Kacprzyk, Janusz, Series Editor, Gomide, Fernando, Advisory Editor, Kaynak, Okyay, Advisory Editor, Liu, Derong, Advisory Editor, Pedrycz, Witold, Advisory Editor, Polycarpou, Marios M., Advisory Editor, Rudas, Imre J., Advisory Editor, Wang, Jun, Advisory Editor, Das, Santosh Kumar, editor, Samanta, Sourav, editor, Dey, Nilanjan, editor, and Kumar, Rajesh, editor

Published
2020
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