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Results for “transmission reconstruction”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Structure of the (110) Ln ScO 3 ( Ln =Gd,Tb,Dy) surfaces

The surface reconstruction on the (110) surface of LnScO 3 (Ln=Gd,Tb,Dy) has been investigated using x-ray photoelectron spectroscopy, atomic force microscopy, and transmission electron diffraction coupled with higher-level density-functional theory methods. The experimental techniques generate constraints on the surface chemistry and structure that are used to inform the theoretical comparison of a number of potential surface structures. The resulting structure is then compared to experimental aberration-corrected transmission electron microscopy results using multislice simulation. The surfaces of both single-crystalline substrates and hydrosauna synthesized nanoparticles exhibit a Sc-rich double layer with a Sc 3 O 4 termination.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Electronic surface reconstruction of TiO 2 nanocrystals revealed by resonant inelastic x-ray scattering

The identification of lattice multiphases in TiO 2 nanocrystals is studied by high resolution transmission electron microscope and electron diffraction patterns. Based on the spectroscopic analysis using soft x-ray absorption and resonant inelastic soft x-ray scattering, it is believed that the oxygen vacancies at the interface exhibit structural distortion of the TiO$^{8-}_6$ cluster around the defect site as for the multiphase lattice. We elucidate that the extra 3d electrons nearby induce the inelastic scattering features with the excitation energy dependence owing to different energy relaxation processes, a characteristic of the electron-phonon coupling or the nature of the electron-hole pair at the intermediate state. The manifold dd excitations driven by the strong interaction between Ti-3d and O-2p electrons are noticeably rich, coexisting on both Ti and O sites. Finally, this sophisticated experiment can advance the perspective of nanocomposite TiO 2 for various interactions of surface Ti 3+ in applications of future devices.

36 MATERIALS SCIENCE↗
NASA NTRS1978

Obtaining a tomographic image from transmission projections

Technique for obtaining tomographic images work directly in signal space and is used to find object configuration by simple summation of density values. Image is reconstructed by precise inverse of scanning. Signal values corresponding to density of projection are added as constant terms along line corresponding to original path between two probes that give rise to that density value.

Heyser, R. C.↗
DOE OSTI2020

Effects of Extended Aqueous Processing on Structure, Chemistry, and Performance of Polycrystalline LiNi x Mn y Co z O 2 Cathode Powders

The prospect of aqueous processing of LiNi x Mn y Co z O 2 (NMC) cathodes has significant appeal to battery manufacturers for the reduction in materials cost, toxicological risk, and environmental impact compared to conventional N -methyl-2-pyrrolidone (NMP)-based processing. However, the effects of aqueous processing of NMC powders at industrial timescales are not well studied, with prior studies mostly focusing on relatively brief water washing processes. Here, we investigate the bulk and surface impacts of extended aqueous processing of polycrystalline NMC powders with different compositions. We demonstrate that at timescales of several hours, polycrystalline NMC is susceptible to intergranular fracture, with the severity of fracture scaling with the NMC nickel content. While bulk crystallinity and composition are unchanged, surface sensitive techniques such as X-ray photoelectron spectroscopy (XPS) and transmission electron microscopy (TEM) indicate that the exposure of water leads to a level of delithiation, nickel reduction, and reconstruction from the layered to rock-salt structure at the surface of individual grains. Dynamic single NMC microparticle compression testing suggests that the resulting mechanical stresses weaken the integrity of the polycrystalline particle and increases susceptibility of intergranular fracture. The initially degraded surfaces along with the increased surface area lead to faster capacity fade and impedance growth during electrochemical cycling. From this work, it is demonstrated that NMC powders require surface or grain boundary modifications to make industrial-scale aqueous cathode processing viable, especially for next-generation nickel-rich NMC chemistries.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2024

Toward quantum networking with frequency-bin qudits

Quantum networking holds tremendous promise in transforming computation and communication. Entangled-photon sources are critical for quantum repeaters and networking, while photonic integrated circuits are vital for miniaturization and scalability. In this talk, we focus on generating and manipulating frequency-bin entangled states within integrated platforms. We encode quantum information as a coherent superposition of multiple optical frequencies; this approach is favorable due to its amenability to high-dimensional entanglement and compatibility with fiber transmission. We successfully generate and measure the density matrix of biphoton frequency combs from integrated silicon nitride microrings, fully reconstructing the state in an 8 × 8 two-qudit Hilbert space, the highest so far for frequency bins. Moreover, we employ Vernier electro-optic phase modulation methods to perform time-resolved measurements of biphoton correlation functions. Currently, we are exploring bidirectional pumping of microrings to generate indistinguishable entangled pairs in both directions, aiming to demonstrate key networking operations such as entanglement swapping and Greenberger–Horne–Zeilinger state generation in the frequency domain.

Myilswamy, Karthik V.↗
DOE OSTI2021

SINGLE: Atomic-resolution structure identification of nanocrystals by graphene liquid cell EM

Analysis of the three-dimensional (3D) structures of nanocrystals with solution-phase transmission electron microscopy is beginning to reveal their unique physiochemical properties. We developed a “one-particle Brownian 3D reconstruction method” based on imaging of ensembles of colloidal nanocrystals using graphene liquid cell electron microscopy. Projection images of differently rotated nanocrystals are acquired using a direct electron detector with high temporal (<2.5 ms) resolution and analyzed to obtain an ensemble of 3D reconstructions. Here, we introduce computational methods required for successful atomic-resolution 3D reconstruction: (i) tracking of the individual particles throughout the time series, (ii) subtraction of the interfering background of the graphene liquid cell, (iii) identification and rejection of low-quality images, and (iv) tailored strategies for 2D/3D alignment and averaging that differ from those used in biological cryo–electron microscopy. Our developments are made available through the open-source software package SINGLE.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1991

Closed-loop motor control using high-speed fiber optics

A closed-loop control system for controlling the operation of one or more servo motors or other controllable devices is described. The system employs a fiber optics link immune to electromagnetic interference, for transmission of control signals from a controller or controllers at a remote station to the power electronics located in proximity to the motors or other devices at the local station. At the remote station the electrical control signals are time-multiplexed, converted to a formatted serial bit stream, and converted to light signals for transmission over a single fiber of the fiber optics link. At the local station, the received optical signals are reconstructed as electrical control signals for the controlled motors or other devices. At the local station, an encoder sensor linked to the driven device generates encoded feedback signals which provide information as to a condition of the controlled device. The encoded signals are placed in a formatted serial bit stream, multiplexed, and transmitted as optical signals over a second fiber of the fiber optic link which closes the control loop of the closed-loop motor controller. The encoded optical signals received at the remote station are demultiplexed, reconstructed and coupled to the controller(s) as electrical feedback signals.

Dawson, Reginald↗
NASA NTRS2003

Morphology of the Vestibular Utricule in Toadfish, Opsanus Tau

The uticle is an otolith organ in the vertebrate inner ear that provides gravitoinertial acceleration information into the vestibular reflex pathways. The aim of the present study was to provide an anatomical description of this structure in the adult oyster toadfish, and establish a morphological basis for interpretation of subsequent functional studies. Light, scanning electron and transmission electron microscopy were applied to visualize the sensory epithelium and its neural innervation. Electrophysiological techniques were used to identify utricular afferents by their response to translation stimuli. Similar to nerve afferents supplying the semicircular canals and lagena, utricular afferents commonly exhibit a short-latency increase of firing rate in response to electrical activation of the central efferent pathway. Afferents were labeled with biocytin either intraaxonally or with extracellular bulk deposits. Light microscope images of serial thick sections were used to make three-dimensional reconstructions of individual labeled afferents to identify the dendritic morphology with respect to epithelial location. Scanning electron microscopy was used to visualize the surface of the otolith mass facing the otolith membrane, and the hair cell polarization patterns of strioler and extrastriolar regions. Transmission electron micrographs of serial thin sections were compiled to create a three-dimensional reconstruction of the labeled afferent over a segment of its dendritic field and to examine the hair cell-afferent synaptic contacts.

Bass, L.↗
DOE OSTI2020

Nucleation and growth of PbSeO 3 , Pb 3 (CO 3 ) 2 (OH) 2 , and Se on the PbSe surfaces by decomposing PbSe in water

PbSe materials are widely researched and utilized in visible-infrared photodetectors, displays, transistors, thermoelectric devices, and photovoltaics. However, the instability of PbSe limits practical utilization. The decomposition mechanisms of PbSe needs to be clarified for guiding targeted design to improve its stability. Here, we studied the decomposition process of PbSe in water, which is exposed to air, by using ex-situ and semi in situ transmission electron microscope (TEM), energy-dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), and electron tomography reconstruction (ETR). We found that, besides water molecules, PbSe particles also react with O 2 and CO 2 that are adsorbed in water from air. Pd 3 (CO 3 ) 2 (OH) 2 , PbSeO 3 , and Se nucleate and grow on the surface of PbSe powders. This work provides understanding of the mechanism of materials nucleation, growth, and decomposition. Furthermore, the findings can be used as a reference to improve the stability and lifetime of PbSe devices.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2026

Strain mapping of three-dimensionally structured two-dimensional materials

Strain plays a crucial role in tuning materials’ properties, influencing their optical, electrical, and chemical performances. In two-dimensional (2D) materials, applied stress often induces out-of-plane deformation, resulting in a more intricate three-dimensional (3D) topography, where mapping the strain remains a challenge due to the limitations of conventional characterization techniques. In this work, we introduce BRIGHT (Bragg-Rod Informed, Gradient-based Height-mapping Technique), an integrated method for reconstructing both the topography and planar strain profile of 3D-structured 2D materials using nanobeam four-dimensional scanning transmission electron microscopy (4D-STEM). We apply BRIGHT to a MoS2-MoSe2 transition metal dichalcogenide (TMD) lateral heterojunctions exhibiting built-in strain and out-of-plane ripples and show that varying heterojunction widths lead to distinct surface morphologies and corresponding changes in the planar strain distribution. These results establish a foundation for more effective strain engineering in 2D materials by accounting for out-of-plane structural features, thereby enabling more precise control of strain-dependent properties.

Mireles, Adan [Rice Univ., Houston, TX (United Sta↗
NASA NTRS1992

A robust coding scheme for packet video

A layered packet video coding algorithm based on a progressive transmission scheme is presented. The algorithm provides good compression and can handle significant packet loss with graceful degradation in the reconstruction sequence. Simulation results for various conditions are presented.

Chen, Yun-Chung↗
NASA NTRS1978

Acoustic holography: Problems associated with construction and reconstruction techniques

The implications of the difference between the inspecting and interrogating radiations are discussed. For real-time, distortionless, sound viewing, it is recommended that infrared radiation of wavelength comparable to the inspecting sound waves be used. The infrared images can be viewed with (IR visible) converter phosphors. The real-time display of the visible image of the acoustically-inspected object at low sound levels such as are used in medical diagnosis is evaluated. In this connection attention is drawn to the need for a phosphor screen which is such that its optical transmission at any point is directly related to the incident electron beam intensity at that point. Such a screen, coupled with an acoustical camera, can enable instantaneous sound wave reconstruction.

Singh, J. J.↗
NASA NTRS1994

Computational Approaches to Vestibular Research

The Biocomputation Center at NASA Ames Research Center is dedicated to a union between computational, experimental and theoretical approaches to the study of neuroscience and of life sciences in general. The current emphasis is on computer reconstruction and visualization of vestibular macular architecture in three-dimensions (3-D), and on mathematical modeling and computer simulation of neural activity in the functioning system. Our methods are being used to interpret the influence of spaceflight on mammalian vestibular maculas in a model system, that of the adult Sprague-Dawley rat. More than twenty 3-D reconstructions of type I and type II hair cells and their afferents have been completed by digitization of contours traced from serial sections photographed in a transmission electron microscope. This labor-intensive method has now been replace d by a semiautomated method developed in the Biocomputation Center in which conventional photography is eliminated. All viewing, storage and manipulation of original data is done using Silicon Graphics workstations. Recent improvements to the software include a new mesh generation method for connecting contours. This method will permit the investigator to describe any surface, regardless of complexity, including highly branched structures such as are routinely found in neurons. This same mesh can be used for 3-D, finite volume simulation of synapse activation and voltage spread on neuronal surfaces visualized via the reconstruction process. These simulations help the investigator interpret the relationship between neuroarchitecture and physiology, and are of assistance in determining which experiments will best test theoretical interpretations. Data are also used to develop abstract, 3-D models that dynamically display neuronal activity ongoing in the system. Finally, the same data can be used to visualize the neural tissue in a virtual environment. Our exhibit will depict capabilities of our computational approaches and some of our findings from their application. For example, our research has demonstrated that maculas of adult mammals retain the property of synaptic plasticity. Ribbon synapses increase numerically and undergo changes in type and distribution (p<0.0001) in type II hair cells after exposure to microgravity for as few as nine days. The finding of macular synaptic plasticity is pertinent to the clinic, and may help explain some. balance disorders in humans. The software used in our investigations will be demonstrated for those interested in applying it in their own research.

Ross, Muriel D.↗
DOE OSTI2020

Electron tomography imaging methods with diffraction contrast for materials research

Transmission electron microscopy (TEM) and scanning transmission electron microscopy (STEM) enable the visualization of three-dimensional (3D) microstructures ranging from atomic to micrometer scales using 3D reconstruction techniques based on computed tomography algorithms. This 3D microscopy method is called electron tomography (ET) and has been utilized in the fields of materials science and engineering for more than two decades. Although atomic resolution is one of the current topics in ET research, the development and deployment of intermediate-resolution (non-atomic-resolution) ET imaging methods have garnered considerable attention from researchers. This research trend is probably not irrelevant due to the fact that the spatial resolution and functionality of 3D imaging methods of scanning electron microscopy (SEM) and X-ray microscopy have come to overlap with those of ET. In other words, there may be multiple ways to carry out 3D visualization using different microscopy methods for nanometer-scale objects in materials. From the above standpoint, this review paper aims to (i) describe the current status and issues of intermediate-resolution ET with regard to enhancing the effectiveness of TEM/STEM imaging and (ii) discuss promising applications of state-of-the-art intermediate-resolution ET for materials research with a particular focus on diffraction contrast ET for crystalline microstructures (superlattice domains and dislocations) including a demonstration of in situ dislocation tomography.

36 MATERIALS SCIENCE↗
DOE OSTI2026

Detector architecture and data flow of the CMS HGCAL Phase-2 Endcap Calorimeter Upgrade

The CMS High Granularity Calorimeter (HGCAL) is the Phase-2 endcap calorimeter upgrade for the High-Luminosity Large Hadron Collider, designed to provide precise spatial, energy, and timing measurements in a high-radiation, high-pileup environment. This work presents an overview of the HGCAL assembly process, detector architecture, and end-to-end data flow. The data flow goes from signal generation in silicon sensors and scintillator tiles through front-end electronics, optical transmission, and back-end data acquisition. The study highlights how the integrated detector, electronics, and readout systems enable efficient event reconstruction and support the physics objectives of the HL-LHC.

Osei Boakye, Prince [Grambling State U.]↗
NASA NTRS1997

The Galileo Spacecraft: A Communications Legacy for Future Space Flight

The Galileo mission to Jupiter has implemented a wide range of telecommunication improvements in response to the loss of it's high gain antenna. Among the communications enhancements that have been made are the use of advanced compression techniques, packetized telemetry, new error correcting codes and algorithms, more efficient modulation, variable transmission data rates, routine ground antenna arraying (even between continents,) extremely sensitive ground receivers, and non-real-time automated data reconstruction. This telecommunications legacy of Galileo will aid in our abillity to conduct a meaningful exploration of the solar system, and beyond, at a reasonable cost.

Galileo↗
NASA NTRS1995

3-D Reconstruction of Macular Type II Cell Innervation Patterns in Space-Flight and Control Rats

A semiautomated method for reconstructing objects from serial thin sections has been developed in the Biocomputation Center. The method is being used to completely, for the first time, type II hair cells and their innervations. The purposes are to learn more about the fundamental circuitry of the macula on Earth and to determine whether changes in connectivities occur under space flight conditions. Data captured directly from a transmission electron microscope via a video camera are sent to a graphics workstation. There, the digitized micrographs are mosaicked into sections and contours are traced, registered and displayed by semiautomated methods. Current reconstructions are of type II cells from the medial part of rat maculas collected in-flight on the Space Life Sciences-2 mission, 4.5 hrs post-flight, and from a ground control. Results show that typical type II cells receive processes from tip to six nearby calyces or afferents. Nearly all processes are elongated and have bouton-like enlargements; some have numerous vesicles. Multiple (2 to 4) processes from a single calyx to a type II cell are common, and approximately 1/3 of the processes innervale 2 or 3 type II cells or a neighboring cluster. From 2% to 6% of the cells resemble type I cells morphologically but have demi-calyces. Thus far, increments in synaptic number in type II cells of flight rats are prominent along processes that supply two hair cells. It is clear that reconstruction methods provide insights into details of macular circuitry not obtainable by other techniques. The results demonstrate a morphological basis for interactions between adjacent receptive fields through feed back-feed forward connections, and for dynamic alterations in receptive field range and activity during preprocessing of linear acceleratory information by the maculas. The reconstruction method we have developed will find further applications in the study of the details of neuronal architecture of more complex systems, to seek out shared organizational properties or neuronal networks and to understand better localization of synaptic changes in altered environments.

Ross, Muriel Dorothy↗
NASA NTRS2003

Parallel Information Processing (Image Transmission Via Fiber Bundle and Multimode Fiber

Growing demand for visual, user-friendly representation of information inspires search for the new methods of image transmission. Currently used in-series (sequential) methods of information processing are inherently slow and are designed mainly for transmission of one or two dimensional arrays of data. Conventional transmission of data by fibers requires many fibers with array of laser diodes and photodetectors. In practice, fiber bundles are also used for transmission of images. Image is formed on the fiber-optic bundle entrance surface and each fiber transmits the incident image to the exit surface. Since the fibers do not preserve phase, only 2D intensity distribution can be transmitted in this way. Each single mode fiber transmit only one pixel of an image. Multimode fibers may be also used, so that each mode represent different pixel element. Direct transmission of image through multimode fiber is hindered by the mode scrambling and phase randomization. To overcome these obstacles wavelength and time-division multiplexing have been used, with each pixel transmitted on a separate wavelength or time interval. Phase-conjugate techniques also was tested in, but only in the unpractical scheme when reconstructed image return back to the fiber input end. Another method of three-dimensional imaging over single mode fibers was demonstrated in, using laser light of reduced spatial coherence. Coherence encoding, needed for a transmission of images by this methods, was realized with grating interferometer or with the help of an acousto-optic deflector. We suggest simple practical holographic method of image transmission over single multimode fiber or over fiber bundle with coherent light using filtering by holographic optical elements. Originally this method was successfully tested for the single multimode fiber. In this research we have modified holographic method for transmission of laser illuminated images over commercially available fiber bundle (fiber endoscope, or fiberscope).

Kukhtarev, Nicholai↗