460 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
South Asian Figurines in the British Museum: Literature Review and Analysis
No full textIn the early twenthieth century in British India, many military officers were also amateur archaeologists. Some of them, including Colonel D.H. Gordon and Colonel D.R. Martin, collected human terracotta figurines. The figurines in this collection came from the northwest of pre-partition India, mostly from villages in the vicinity of Peshawar in Pakistan. They were bought from farmers or antiquities dealers. Thus this is a surface collection. The figurines were then sold or donated to the British Museum. There they were stored without being studied.
This purpose of this thesis is two-fold: 1) to review the literature on South Asian human figurines, and 2) to analyze and interpret a collection of figurines that has not so far been published. The analysis includes a description of the characteristics of the figurines, and interpretations of their functions and meanings. There are four major types of figurines, based on decorations and facial features: Sar Dheri, Sahri Bahlol, Hellenistic and “other”. The Sar Dheri figurines with rosettes may represent an unknown folk deity as the decorations are not the symbol of any deity that appears in Hindu, Jain or Buddhist mythology. The Sahri Bahlol figurines greatly resemble those figurines identified as Naigameśīs in other excavation reports. The analysis ends by proposing further research in South Asian terracotta figurines that would lead to a detailed history of the evolution of figurines in South Asia from Mehrgarh to the present
Effect of high voltage on the structure and electrochemistry of LiNi0.5Mn0.5O2: A joint experimental and theoretical study
No full textA combination of neutron diffraction (ND), Li-6 magic-angle spinning NMR, electrochemistry, and first principles calculations have been used to determine and rationalize the structural changes that occur during cycling of the layered material Lix(Ni0.5Mn0.5)O-2 (x = 1), synthesized via the hydroxide route. ND and 6Li NMR experiments confirm that Li is lost from the transition metal (TM) layers, very early on in the charge process. On charging to higher voltages (above 4.5 V), the Li is lost from the tetrahedral and residual Li octahedral sites in the Li layers. This process is accompanied by a migration of more than 75% of the Ni ions originally present in the Li layers into the TM layers, to occupy the sites vacated by Li. Calculations suggest that (i) these Ni migrations occur via the tetrahedral sites, (ii) activation energies for migration depend strongly on the original position of the Ni ions in the Li layers though the driving force for migration is large (> 1 eV), and (iii) because neither Ni3+ nor Ni4+ is stable in the tetrahedral site, migration will not occur once the Ni ions in the Li layers are oxidized to Ni3+ or Ni4+. Electrochemical measurements (open circuit voltage, OCV, and galvanostatic mode) are consistent with a high voltage process (approximately 4.6 V) associated with a large activation energy. The new Ni sites in the TM layers are not necessarily stable, and on discharge, 60% of the ions return to the Li layers. In particular, Ni ions surrounded by six Mn4+ ions are found (in the calculations) to be the least stable. Because the Li ions originally in the TM layers in the as-synthesized sample are predominantly in this environment, this is consistent with the Ni migration observed experimentally. Materials charged to 5.3 V can be cycled reversibly with stable capacities of over 180 mAh g(-1).The work was supported by the Assistant
Secretary for Energy Efficiency and Renewable Energy, Office of FreedomCAR and Vehicle Technologies of the U.S. DOE
under Contract No. DE-AC03-76SF00098, via subcontracts No.6517748 and 6517749 with the Lawrence Berkeley National Laboratory. We would also like to acknowledge the support
form the Center for Materials Science and Engineering, MIT, and the MRSEC program of the NSF under award number DMR 02-13282. Y.S.-H. acknowledges the Office of Naval Research Young Investigator Award No. N00014-03-10448 for financial support. The ISIS Facility of the Rutherford Appleton Labora-tory is thanked for access to GEM. This work has benefited from the use of NPDF at the Lujan Center at the Los Alamos Neutron Science Center, funded by the DOE Office of Basic Energy Sciences (BES), Los Alamos National Laboratory, and the DOE under Contract No. W-7405-ENG-36. The upgrade
of NPDF has been funded by NSF through Grant DMR 00-76488. This work has benefited from the use of the Intense Pulsed Neutron Source at Argonne National Laboratory. This
facility is funded by the U.S. DOE under Contract No. W-31-109-ENG-38. Use of the NSLS, Brookhaven National Laboratory,
was supported by the U.S. DOE, Office of BES, under Contract No. DE-AC02-98CH10886. We are grateful for the assistance given to us at the different beam lines from Thomas
Proffen (NPDF, LANL), Winfried Kockelmann (GEM, ISIS),Yongjae Lee (X7A, NSLS), James Richardson, Evan Maxey, and Ashfia Huq (GPPD, IPNS). We thank Jordi Cabana for
electrochemical measurements as well as Matthias Gutmann and Alan Soper for their help in neutron data analysis
Design of a tool for computing belief sets of epistemic specifications
No full textAbstract not availabl
New diorganotin(IV) complexes of salicylaldehyde based hydrazones bearing furan heterocycle moiety: X-ray structural investigation of dimethyltin(IV) and diphenyltin(IV) complexes
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