1,691 research outputs found
Supplemental Material - Low awareness but high acceptability of pre-exposure prophylaxis for HIV among men who have sex with men and transgender persons in Delhi, India
No full textSupplemental Material for Low awareness but high acceptability of pre-exposure prophylaxis for HIV among MSM and transgender persons in Delhi, India by Adhish Kumar Sethi, Partha Haldar, Sanjay Kumar Rai, Shashi Kant, Shobini Rajan, Parveen Kumar, Jitendra Kumar Mishra and Bhawani Singh in International Journal of STD & AIDS</p
Supplemental Material - Low awareness but high acceptability of pre-exposure prophylaxis for HIV among men who have sex with men and transgender persons in Delhi, India
No full textSupplemental Material for Low awareness but high acceptability of pre-exposure prophylaxis for HIV among MSM and transgender persons in Delhi, India by Adhish Kumar Sethi, Partha Haldar, Sanjay Kumar Rai, Shashi Kant, Shobini Rajan, Parveen Kumar, Jitendra Kumar Mishra and Bhawani Singh in International Journal of STD & AIDS</p
sj-docx-1-pie-10.1177_09544089231205778 - Supplemental material for Mechanical and microstructural characteristics of AA6082 using thermal equal channel angular pressing for structural applications
No full textSupplemental material, sj-docx-1-pie-10.1177_09544089231205778 for Mechanical and microstructural characteristics of AA6082 using thermal equal channel angular pressing for structural applications by Sunil Kadiyan, Parveen Kumar, Vikas Goyat, Gyander Ghangas, BS Dehiya and Chander Prakash in Proceedings of the Institution of Mechanical Engineers, Part E: Journal of Process Mechanical Engineering</p
An insight into photo-catalytic degradation mechanism of persistent pollutants with transition metal oxides and their composites: Photocatalysis mechanism, rate affecting parameters, and removal pathways
No full textPhotocatalysis process in pollution control applications has concerned considerable attention given the increasing seriousness of environmental challenges including water, air, and soil. The present review of state-of-the-art research focuses on the current research trends in the development and application of transition metal oxides [TMOs]-based photocatalysis systems to improve the removal trends of organic pollutants from wastewater and photocatalytic mechanisms. For easy understanding, the up-to-date progress in the construction and design of heterojunction systems such as Type I/Type II heterojunction, p-n heterojunction, p-n-p heterojunction, Z-scheme heterojunction, and C-scheme heterojunction have been defined in detail into four categories based on the TMOs composition and mode of application. This review focuses on the detailed assessment of supported and suspended catalysts, their specific need, methodologies for performance evaluation, and the main factors that influence the removal mechanism. In addition, all the possible advanced and fundamental mechanisms of dye degradation, especially azo dye, triphenylmethane, and indigo dye with different categories of catalysts, are summarized. The current challenges and researcher’s approaches on how they successfully solve the drawbacks as well as future research trends in TMOs-based photocatalytic systems are discussed
Development of Wire and Arc Additive Manufacturing Process for Deposition of Ni- Based Super Alloy
No full textWire Arc Additive Manufacturing (WAAM) is an innovative form of 3D printing that uses an electric arc as a heat source to melt metal wire, which is then deposited layer by layer to create complex metal parts. This technique achieves high deposition rates and allows the building of large-scale components with significant cost and material savings compared to traditional manufacturing methods. In the past, a variety of materials have been fabricated through WAAM. However, very little work has been done using WAAM on nickel-based super-alloys. Nickel-based super-alloys are a class of metallic alloys known for their exceptional high-temperature strength, resistance to creep deformation, and resistance to corrosion and oxidation. The excellent combination of these properties makes these materials ideal for use in jet engines, gas turbines, power plants, and other high-temperature applications. Manufacturing these complex design components of nickel-based superalloys using traditional methods is challenging and expensive. To address this issue, the current research focuses on the feasibility and development of the WAAM process as a promising alternative for producing nickel-based components.
The initial focus is on establishing a robust GMAW-based WAAM process. This involves optimizing the gas metal arc welding (GMAW) process parameters, a key element of WAAM. Through numerous trials, the main aim is to identify the ideal settings for factors such as current, voltage, and welding speed. This study uses a bi-directional, low-cost, GMAW-based wire arc additive manufacturing (WAAM) setup to deposit aerospace-grade super-alloy IN718. Orthogonally designed experiments are carried out to optimize process parameters for single and multilayer bead geometries.
Additionally, ANOVA analysis and S/N ratio plots are employed to optimize process parameters for bead characteristics such as width, reinforcement, penetration, dilution, WRFF, WPSF, surface waviness, and effective area. Furthermore, the effect of heat input is discussed. The study results indicate that increased heat input increases bead parameters like bead width, reinforcement, dilution, penetration, and weld form factor while negatively impacting the weld shape factor and wetting angle.
After optimizing process parameters, characterizations of WAAM-deposited materials were done based on metallurgical and mechanical testing. The metallurgical analysis includes optical microscopy (OM), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and electron backscatter diffraction (EBSD). The mechanical analyses were done based on hardness and tensile testing. These tests provide insights into the microstructure, phases present, elemental composition, grain orientation, and material strength.
The microstructural examination reveals that a high heat input produces a coarse grain structure with an average grain size of 72.29 µm. In contrast, a low heat input produces a finer grain structure with an average grain size of 32.12 µm and smaller Laves phases. The XRD analysis shows the presence of NbC and TiC phases in the low heat input sample, enhancing the deposited material's mechanical properties. The multilayer wall structures fabricated with high heat input demonstrate more uniformity in shape and less waviness than those fabricated with low heat input. Tensile testing results indicate that the low heat input sample exhibits higher strength (775.82 MPa) than the high heat input sample (741.07 MPa). This increased strength is attributed to the smaller grain structure and higher hardness (278.11 HV) observed in the low heat input sample compared to the high heat input sample (257.26 HV). The EBSD analysis further confirms that the low heat input sample has a highly textured surface, more grain boundary lengths, and larger grain boundary orientation, which contributes to its superior mechanical properties.
This study also provides insights into cooling environments and thermal management techniques for WAAM of IN718 components. The material was deposited under four different heat-input conditions, using either air or water cooling. The layers were deposited in a normal atmospheric environment with air cooling, while water cooling involved depositing the material inside a water tank with varying water levels. To validate the air- and water-cooling thermal management techniques, IN718 single-pass, and multilayer linear walls were deposited under four different heat-input conditions. Temperature profiles were recorded during single-layer depositions, and geometric and microstructural features were examined. The SEM analysis revealed that the microstructure in the building direction was non-homogeneous compared to that in the deposition direction.
Additionally, water cooling significantly influenced bead characteristics, such as wall width and height. The grain size and anisotropy of the mechanical properties decreased with water cooling. Therefore, water cooling is economical and efficient in mitigating excessive heat accumulation in WAAM-deposited IN718 components.
Further, this study also examines the effects of shielding gases at various heat inputs on the bead geometry, microstructure evolution, and mechanical properties of Inconel 718 deposited by WAAM. Bead-on-plate experiments were conducted with the CMT technique of GMAW, utilizing Taguchi’s L9 orthogonal array. The factor effects, their contributions, and optimal levels were analyzed using ANOVA and S/N ratio approaches. To determine heat input, the dynamic characteristics of the welding power source were recorded and processed.
The study found increased heat input led to more pronounced bead geometry characteristics and a wider heat-affected zone (HAZ). Increasing the CO2 concentration in the Ar + CO2 mixture altered the weld texture from silver metallic (with pure Ar) to grey with 2.5% CO2 and light yellow with 20% CO2. Higher bead width, reinforcement, penetration, and dilution were observed with an Ar 20% CO2 mix. Beads formed with 2.5% CO2 were continuous and smoother at all heat inputs. Welds prepared in a 100% Ar shielding environment exhibited higher hardness than those with 2.5% CO2 and 20% CO2 mixtures. Higher concentrations of Nb-rich precipitates, identified through SEM-EDS analysis, contributed to increased strength.
Finally, the project culminated in a comparative analysis of two WAAM variants: CMT-WAAM and GMAW-WAAM. CMT-WAAM provides a more controllable arc with lower spatter, potentially reducing porosity and improving bead geometry. A comparison of surface waviness and mechanical properties shows that waviness is lower, whereas strength is higher in CMT WAAM components. Understanding these distinctions empowers us to decide the most suitable WAAM approach for specific applications
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No full textPublished in book entitled as Human Impact on Desert Environment (Eds. Partap Narain , S.Kathju, Amalakr, M.P. Singh & Parveen Kumar) Published by Arid Zone Research Association of India & Scientific Publishers (India) JodhpurNot AvailableNot Availabl
Clinical Pharmacology in the UK, c.1950-2000: Industry and Regulation
No full textAnnotated and edited transcript of a Witness Seminar held on 25 September 2007. Introduction by Professor Parveen Kumar, Barts and the London School of Medicine and Dentistry, University of London.First published by the Wellcome Trust Centre
for the History of Medicine at UCL, 2008. ©The Trustee of the Wellcome Trust, London, 2008.All volumes are freely available online at: www.history.qmul.ac.uk/research/modbiomed/wellcome_witnesses/Annotated and edited transcript of a Witness Seminar held on 25 September 2007. Introduction by Professor Parveen Kumar, Barts and the London School of Medicine and Dentistry, University of London.Annotated and edited transcript of a Witness Seminar held on 25 September 2007. Introduction by Professor Parveen Kumar, Barts and the London School of Medicine and Dentistry, University of London.Annotated and edited transcript of a Witness Seminar held on 25 September 2007. Introduction by Professor Parveen Kumar, Barts and the London School of Medicine and Dentistry, University of London.Annotated and edited transcript of a Witness Seminar held on 25 September 2007. Introduction by Professor Parveen Kumar, Barts and the London School of Medicine and Dentistry, University of London.Annotated and edited transcript of a Witness Seminar held on 25 September 2007. Introduction by Professor Parveen Kumar, Barts and the London School of Medicine and Dentistry, University of London.Annotated and edited transcript of a Witness Seminar held on 25 September 2007. Introduction by Professor Parveen Kumar, Barts and the London School of Medicine and Dentistry, University of London.Clinical pharmacology in the UK in the 1950s and 1960s was an exciting profession. Many important new drugs were developed and brought to market and a more systematic knowledge of drug effects in humans was needed, as well as ensuring the safety and efficacy of new and existing drugs, especially following the unexpected problems arising from the use of thalidomide. This Witness Seminar followed an earlier meeting on the history of the general development of clinical pharmacology and focuses on the development of clinical pharmacology in pharmaceutical companies and drug regulation. Professor Rod Flower chaired the meeting of clinical pharmacologists and others who shaped the discipline, which discussed the main centres of influence; the attraction to clinical pharmacologists of working in industry; whether the decline in the number of academic clinical pharmacologists was paralleled in drug companies; what drove drug regulation; and the relationships between companies and regulatory authorities. Participants included Dr Jeffrey Aronson, Professor Nigel Baber, Sir Alasdair Breckenridge, Sir Iain Chalmers, Professor Joe Collier, Professor Donald Davies, Dr Peter Fletcher, Dr Arthur Fowle, Professor Sir Charles George, Professor David Grahame-Smith, Professor John Griffin, Dr Andrew Herxheimer, Professor Ray Hill, Dr Peter Lewis, Dr Tim Mant, Professor Denis McDevitt, Professor Michael Orme, Dr Anthony Peck, Professor Brian Prichard, Professor Sir Michael Rawlins, Professor John Reid, Professor Philip Routledge, Dr Julian Shelley, Dr Robert Smith, Professor Cameron Swift, Professor Tilli Tansey, Dr Duncan Vere, and the late Professor Owen Wade. Reynolds L A, Tansey E M. (eds) (2008) Clinical pharmacology in the UK, c. 1950–2000: Industry and regulation. Wellcome Witnesses to Twentieth Century Medicine, vol. 34. London: The Wellcome Trust Centre for the History of Medicine at UCL.The Wellcome Trust Centre for the History of Medicine at UCL is funded by the Wellcome Trust, which is a registered charity, no. 210183
Friction and wear behaviour of hypereutectic Al-Si alloy/steel tribopair under dry and lubricated conditions
No full textSynthesis and tribological properties of graphene: A review
No full textThe target of this review is to explore the fundamental tribological behaviour of graphene, the first existing two-dimensional (2-D) material and evaluate its performance as a self-lubricating material. The importance and potential impact of this new class of material was recognised by the whole scientific community when the Noble prize was awarded to Geim and Konstantin Novoselov for their discovery and development of graphene in 2010. Graphene is the strongest material, chemically and thermally stable, gas-impermeable, and atomically-thin. The fundamental tribological behaviour of graphene and other 2-D materials under sliding conditions is recently being studied. Mainly, the wear of graphene has hardly been investigated. In this paper, the latest developments in tribological applications of graphene, and preparation methods are reviewed. It is shown that various graphene coatings, graphene as lubricant additive and as reinforcement in metal matrix can be successfully employed to decrease friction and wear in tribological applications. A comprehensive review is provided with the aim to analyse such properties of graphene. Moreover, the application of graphene in the field of tribology for reducing friction and wear for better lubrication will be explored
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