503 research outputs found
sj-docx-1-sen-10.1177_02670844241240387 - Supplemental material for Electrochemical behaviour of sputter-coated titanium films on AZ31 magnesium alloy
No full textSupplemental material, sj-docx-1-sen-10.1177_02670844241240387 for Electrochemical behaviour of sputter-coated titanium films on AZ31 magnesium alloy by Sundeep Kumar Marndi, Raman Pachaiappan, Amirthapandian Sankarakumar and Paramasivam Thangadurai in Surface Engineering</p
Supplementary_file_revised_1 – Supplemental material for Paleoenvironmental shifts spanning the last ~6000 years and recent anthropogenic controls inferred from a high-altitude temperate lake: Anchar Lake, NW Himalaya
No full textSupplemental material, Supplementary_file_revised_1 for Paleoenvironmental shifts spanning the last ~6000 years and recent anthropogenic controls inferred from a high-altitude temperate lake: Anchar Lake, NW Himalaya by Aasif Mohmad Lone, Hema Achyuthan, Rayees Ahmad Shah, Satish Jadgeo Sangode, Pankaj Kumar, Sundeep Chopra and Rajveer Sharma in The Holocene</p
Generated holographic stereograms in photorefractive polymer
No full textThesis (S.M.)--Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2012.Cataloged from PDF version of thesis.Includes bibliographical references (p. 77-80).This thesis aims to assess the feasibility of an updatable three-dimensional display based on the direct fringe writing of computer-generated holographic gratings into a novel photorefractive polymer. The photorefractive polymer in question has been developed by Nitto Denko Technical Corporation and has many attractive properties for the 3-D display application, including long image persistence, rapid erasure, high diffraction efficiency, and large area; however, current holographic display systems based around its use involve interference methods that complicate their optical and computational architectures. The direct fringe writing architecture under question is poised as a simplifying and enhancing alternative to previous demonstrations of updatable holographic displays in photorefractive polymeric materials based around such conventional interference-based holographic stereogram techniques. In addition to simplifying optical architectures, direct fringe writing can allow for complete control of recorded hologram characteristics; interference fringes can be computed to simulate any arbitrary reference beam geometry and wavefront curvature. The system concept - comprised of fringe pattern generation on computer, fringe pattern transfer from SLM to photorefractive polymer, and spatial multiplexing for large-image generation - reintroduces accommodation cues to the resulting holographic images and represents a reduction of system footprint, complexity, and cost relative to the current interference-based systems. The adaptation of the Diffraction Specific Coherent Panoramagram fringe computation method - originally developed to drive AOM-based holographic displays at video rates while preserving all depth cues, including accommodation - to the current display architecture is presented and methods for direct fringe transfer from SLM to photorefractive polymer are depicted. Such methods for direct fringe writing are explored in simulation and experiment. Theoretical arguments for system performance are formulated in the context of a wave optics-based system analysis. Preliminary results of horizontal parallax-only images on this display are presented and directions for performance improvements and system extensions are explored.by Sundeep Jolly.S.M
A commercial approach towards fabrication of bulk and nano phosphors converted highly-efficient white LEDs
No full textHerein, we report a strategy to synthesize a highly efficient yellow light emitting Y3−xAl5O12:Cex (x = 0.03 to 0.3) based bulk as well as nano (rod-shaped) phosphors, which are the main component of solid state white light-emitting diodes (WLEDs). The as-synthesized phosphors were well characterized by several experimental techniques related to material characterization and spectroscopy. The bulk and nano phosphors emit with maximum photoluminescence intensities at 549 and 530 nm, respectively, upon excitation at a wavelength of 468 nm. These phosphors exhibit higher photoluminescence intensity as compared to commercially available bulk phosphors coated on WLED strips. Moreover, the integration of commercially available InGaN blue LED strips with the synthesized bulk and nano phosphors demonstrates better CIE coordinates and lower colour temperature with high brightness (>81% quantum yield) compared to commercially available WLED-based strips, lanterns and torches. These highly efficient light-emitting phosphors are a feasible candidate for potential use in commercial WLED applications
Holographic augmented reality : towards near-to-eye electroholography via guided wave acousto-optics
No full textThesis: Ph. D., Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Sciences, 2019Cataloged from PDF version of thesis.Includes bibliographical references (pages 121-128).Near-to-eye displays act to directly project imagery into a viewer's eye and can range in instantiation from extremely simple (such as an optical viewfinder) to more complex immersive displays for applications in virtual and augmented reality. Many current schemes for near-to-eye display employ stereoscopic techniques; however, such instantiations do not consistently present correct accommodation and vergence cues to the viewer, limiting their potential for seamless, comfortable augmented reality applications. Recent techniques based around light-field display methods show promise in the delivery of consistent depth cues although their applicability in presenting scenery with jointly high spatial and angular resolution is limited.Electroholographic displays have been shown to provide the highest degree of visual realism and consistency amongst cues to depth relative to all competing technologies for 3-D display, and several recent instantiations based around pixelated spatial light modulators have shown their utility for near-to-eye display applications. However, constraints on available space-bandwidth product in such pixelated modulators limit the usable system dtendue, resulting in reduced eyebox or field of view. In contrast, waveguide spatial light modulators offer the potential for displays with extremely high space-bandwidth product, compact form factors, and full-color operation via frequency-division multiplexing. This dissertation aims to assess the feasibility of waveguide-based electroholography for near-to-eye augmented reality display.In particular, such feasibility is assessed through (i) a static set of near-to- eye holograms computed via iterative Fresnel domain techniques and fabricated via grayscale electron-beam lithography and(2) the design and analysis of a fully monolithic photonic platform for transparent, flat-panel holographic display requiring no supporting optics and implemented via anisotropic leaky-mode coupling in conjunction with integrated Bragg-regime diffractive combiner optics in lithium niobate. Furthermore, this dissertation presents a fabrication modality for multiscale, transparent, flat-panel holographic video displays based around femtosecond direct laser writing. Methods for and results in the integration of anisotropic waveguides, volume Bragg reflection holograms, and surface acoustic wave transducers in a lithium niobate substrate are depicted.by Sundeep Jolly.Ph. D.Ph.D. Massachusetts Institute of Technology, School of Architecture and Planning, Program in Media Arts and Science
Auxeticity in biosystems: an exemplification of its effects on the mechanobiology of heterogeneous living cells
No full textAuxeticity (negative Poisson’s ratio) is the unique mechanical property found in an extensive variety of materials, such as metals, graphene, composites, polymers, foams, fibers, ceramics, zeolites, silicates and biological tissues. The enhanced mechanical features of the auxetic materials have motivated scientists to design, engineer and manufacture man-made auxetic materials to fully leverage their capabilities in different fields of research applications, including aeronautics, medical, protective equipments, smart sensors, filter cleaning, and so on. Atomic force microscopy (AFM) indentation is one of the most widely used methods for characterizing the mechanical properties and response of the living cells. In this contribution, we highlight main consequences of auxeticity for biosystems and provide a representative example to quantify the effect of nucleus auxeticity on the force response of the embryonic stem cells. A parametric study has been conducted on a heterogeneous stem cell to evaluate the effect of nucleus diameter, nucleus elasticity, indenter’s shape and location on the force-indentation curve. The developed model has also been validated with the recently reported experimental studies available in the literature. Our results suggest that the nucleus auxeticity plays a profound role in cell mechanics especially for large size nucleus. We also report the mechanical stresses induced within the hyperelastic cell model under different loading conditions that would be quite useful in decoding the interrelations between mechanical stimuli and cellular behavior of auxetic biosystems. Finally, current and potential areas of applications of our findings for regenerative therapies, tissue engineering, 3 D/4D bioprinting, and the development of meta-biomaterials are discussed
Coupled multiphysics modelling of sensors for chemical, biomedical, and environmental applications with focus on smart materials and low-dimensional nanostructures
No full textLow-dimensional nanostructures have many advantages when used in sensors compared to the traditional bulk materials, in particular in their sensitivity and specificity. In such nanostructures, the motion of carriers can be confined from one, two, or all three spatial dimensions, leading to their unique properties. New advancements in nanosensors, based on low-dimensional nanostructures, permit their functioning at scales comparable with biological processes and natural systems, allowing their efficient functionalization with chemical and biological molecules. In this article, we provide details of such sensors, focusing on their several important classes, as well as the issues of their designs based on mathematical and computational models covering a range of scales. Such multiscale models require state-of-the-art techniques for their solutions, and we provide an overview of the associated numerical methodologies and approaches in this context. We emphasize the importance of accounting for coupling between different physical fields such as thermal, electromechanical, and magnetic, as well as of additional nonlinear and nonlocal effects which can be salient features of new applications and sensor designs. Our special attention is given to nanowires and nanotubes which are well suited for nanosensor designs and applications, being able to carry a double functionality, as transducers and the media to transmit the signal. One of the key properties of these nanostructures is an enhancement in sensitivity resulting from their high surface-to-volume ratio, which leads to their geometry-dependant properties. This dependency requires careful consideration at the modelling stage, and we provide further details on this issue. Another important class of sensors analyzed here is pertinent to sensor and actuator technologies based on smart materials. The modelling of such materials in their dynamics-enabled applications represents a significant challenge as we have to deal with strongly nonlinear coupled problems, accounting for dynamic interactions between different physical fields and microstructure evolution. Among other classes, important in novel sensor applications, we have given our special attention to heterostructures and nucleic acid based nanostructures. In terms of the application areas, we have focused on chemical and biomedical fields, as well as on green energy and environmentally-friendly technologies where the efficient designs and opportune deployments of sensors are both urgent and compelling.Natural Sciences and Engineering Research Council (NSERC) of CanadaCanada Research Chairs (CRC) Progra
Fluid–structure interaction and non-fourier effects in coupled electro-thermo-mechanical models for cardiac ablation
No full textIn this study, a fully coupled electro-thermo-mechanical model of radiofrequency (RF)-assisted cardiac ablation has been developed, incorporating fluid–structure interaction, thermal relaxation time effects and porous media approach. A non-Fourier based bio-heat transfer model has been used for predicting the temperature distribution and ablation zone during the cardiac ablation. The blood has been modeled as a Newtonian fluid and the velocity fields are obtained utilizing the Navier–Stokes equations. The thermal stresses induced due to the heating of the cardiac tissue have also been accounted. Parametric studies have been conducted to investigate the effect of cardiac tissue porosity, thermal relaxation time effects, electrode insertion depths and orientations on the treatment outcomes of the cardiac ablation. The results are presented in terms of predicted temperature distributions and ablation volumes for different cases of interest utilizing a finite element based COMSOL Multiphysics software. It has been found that electrode insertion depth and orientation has a significant effect on the treatment outcomes of cardiac ablation. Further, porosity of cardiac tissue also plays an important role in the prediction of temperature distribution and ablation volume during RF-assisted cardiac ablation. Moreover, thermal relaxation times only affect the treatment outcomes for shorter treatment times of less than 30 s.Natural Sciences and Engineering Research Council (NSERC) of CanadaCanada Research Chairs (CRC) Progra
Thermal ablation of biological tissues in disease treatment: A review of computational models and future directions
No full textPercutaneous thermal ablation has proven to be an effective modality for treating both benign and malignant tumours in various tissues. Among these modalities, radiofrequency ablation (RFA) is the most promising and widely adopted approach that has been extensively studied in the past decades. Microwave ablation (MWA) is a newly emerging modality that is gaining rapid momentum due to its capability of inducing rapid heating and attaining larger ablation volumes, and its lesser susceptibility to the heat sink effects as compared to RFA. Although the goal of both these therapies is to attain cell death in the target tissue by virtue of heating above 50°C, their underlying mechanism of action and principles greatly differs. Computational modelling is a powerful tool for studying the effect of electromagnetic interactions within the biological tissues and predicting the treatment outcomes during thermal ablative therapies. Such a priori estimation can assist the clinical practitioners during treatment planning with the goal of attaining successful tumour destruction and preservation of the surrounding healthy tissue and critical structures. This review provides current state-of-the-art developments and associated challenges in the computational modelling of thermal ablative techniques, viz., RFA and MWA, as well as touch upon several promising avenues in the modelling of laser ablation, nanoparticles assisted magnetic hyperthermia and non-invasive RFA. The application of RFA in pain relief has been extensively reviewed from modelling point of view. Additionally, future directions have also been provided to improve these models for their successful translation and integration into the hospital work flow
Specific polarizability of sand-clay mixtures with varying ethanol concentration
No full textI utilize the concept of specific polarizability (cs), represented as the ratio of mineral-fluid interface polarization per pore-normalized surface area Sp, to emphasize the influence of clay mineralogy and fluid chemistry on complex conductivity (CC) measurements. CC measurements were performed on kaolinite- and illite- sand mixtures as a function of varying ethanol (EtOH) concentration (10% and 20% v/v). Specific surface area of each clay type and Ottawa sand was determined by nitrogen gas adsorption-BET method. I also calculated porosity and saturation of each mixture based on weight loss of dried samples. Debye decomposition, a phenomenological model, was applied to the CC data to determine normalized chargeability (mn). The cs¬ estimates from previous CC measurements for bentonite-sand mixtures were compared with our dataset. The cs for all sand-clay mixtures decreased as the EtOH concentration increased from 0% to 10% to 20%. We observe similar responses to clay-driven polarization for all sand-clay mixtures. Analysis of variance (ANOVA) with a level of significance α = 0.05 found that suppression in cs responses with increasing EtOH concentration statistically vary for all sand-clay mixtures but the confidence level for cs is low. On the other hand, real conductivity showed only small changes with increasing EtOH concentration from 10% to 20%. The cs estimates reflect the sensitivity of CC measurements to alteration in surface chemistry at the available surface adsorption sites (internal and external) for different clay types assumed to result from chemical ion exchange at clay surface and kinetic reactions in the electrical double layer of the clay-water-EtOH media.M.S.Includes bibliographical referencesby Sundeep Sharm
- …
