Edge-Geometry High-Tx SNS Weak Links on Silicon-on-Sapphire Substrates
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silicon-on-sapphire (SOS) multilayer buffer system↗
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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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High-Q mechanical resonators based on carbon nanotubes
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nanotubes↗
Transition Edge YBa(sub 2)Cu(sub 3)O(sub 7-x) Microbolometers for Infrared Staring Arrays
High-temperature superconducting staring arrays are potentially important for both space and terrestrial applications which require the combination of high sensitivity over a broad wavelength range and relatively high temperature operation. In many such array applications sensitivity is more important than speed of response. Thus, it is desirable to design low-thermal-mass pixels that are thermally isolated from the substrate. To this end, Johnson, et al. at Honeywell have fabricated meander lines of YBCO sandwiched between layers of silicon nitride on silicon substrates. The silicon was etched out from under each YBCO meander line to form low-thermal-mass, thermally isolated microbolometers.
infrared staring arrays↗
YBCO/Metal Oxide/YBCO Edge-Geometry Josephson Device with Equitaxial Insulator Overlayers for High-Temperature Superconductive Electronics
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Superconductor-Normal-Superconductor (SNS)↗
High-T(sub c) Edge-geometry SNS Weak Links on Silicon-on-sapphire Substrates
High-quality superconductor/normal-metal/superconductor(SNS) edge-geometry weak links have been produced on silicon-on-sapphire (SOS) substrates using a new SrTiO(sub 3)/'seed layer'/cubic-zirconia (YS2) buffer system.
high-T↗
Microdevices lab and nanotube overview
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carbon nanotubes↗
Carbon nanotube field emitters for nanoklystrons and other high frequency tube sources
Traditional submillimeter-wave vacuum tube sources, now available only from the former Soviet Union, have been a mainstay for generating modest amounts (mW) of narrow band (phase lockable) tunable CW RF power at frequencies from 50 to 1200 GHz.
carbon nanotube↗
Carbon nanotube Schottky diodes using Ti-Schottky and Pt-ohmic contacts for high frequency applications
We have demonstrated Schottky diodes using semiconducting single-walled nanotubes (s-SWNTs) with titanium Schottky and platinum Ohmic contacts for high-frequency applications. The diodes are fabricated using angled evaporation of dissimilar metal contacts over an s-SWNT. The devices demonstrate rectifying behavior with large reverse bias breakdown voltages of greater than 15 V. To decrease the series resistance, multiple SWNTs are grown in parallel in a single device, and the metallic tubes are burnt-out selectively. At low biases these diodes showed ideality factors in the range of 1.5 to 1.9. Modeling of these diodes as direct detectors at room temperature at 2.5 terahertz (THz) frequency indicates noise equivalent powers (NEP) potentially comparable to that of the state-of-the-art gallium arsenide solid-state Schottky diodes, in the range of 10-13 W(square root)xHz.
semiconducting↗
Managing the On-Board Data Storage, Acknowledgement and Retransmission System for Spitzer
The Spitzer Space Telescope has a two-phase downlink system. Recorded data are transmitted during one telecom session. Then commands are sent during the next session to delete those data that were received on the ground and to retransmit those data that were missed. We must build science sequences that are as efficient as possible to make the best use of our supply of liquid helium. One way to improve efficiency is to use only the minimum time needed during telecom sessions to transmit the predicted volume of data. But, we must also not fill the on-board storage and must allow enough time margin to retransmit missed data. We describe tools and procedures that allow us to build science sequences that are single-fault tolerant in this regard and that allow us to recover quickly and safely from anomalies that affect the receipt or acknowledgment (i.e. deletion) of data.
on-board storage↗
Spaceflight Alters Bacterial Gene Expression and Virulence and Reveals Role for Global Regulator Hfq
A comprehensive analysis of both the molecular genetic and phenotypic responses of any organism to the spaceflight environment has never been accomplished due to significant technological and logistical hurdles. Moreover, the effects of spaceflight on microbial pathogenicity and associated infectious disease risks have not been studied. The bacterial pathogen Salmonella typhimurium was grown aboard Space Shuttle mission STS-115 and compared to identical ground control cultures. Global microarray and proteomic analyses revealed 167 transcripts and 73 proteins changed expression with the conserved RNA-binding protein Hfq identified as a likely global regulator involved in the response to this environment. Hfq involvement was confirmed with a ground based microgravity culture model. Spaceflight samples exhibited enhanced virulence in a murine infection model and extracellular matrix accumulation consistent with a biofilm. Strategies to target Hfq and related regulators could potentially decrease infectious disease risks during spaceflight missions and provide novel therapeutic options on Earth.
Wilson, J. W.↗
Initial Performance Assessment of CALIOP
The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP, pronounced the same as "calliope") is a spaceborne two-wavelength polarizatio n lidar that has been acquiring global data since June 2006. CALIOP p rovides high resolution vertical profiles of clouds and aerosols, and has been designed with a very large linear dynamic range to encompas s the full range of signal returns from aerosols and clouds. CALIOP is the primary instrument carried by the Cloud-Aerosol Lidar and Infrar ed Pathfinder Satellite Observations (CALIPSO) satellite, which was l aunched on April, 28 2006. CALIPSO was developed within the framework of a collaboration between NASA and the French space agency, CNES. I nitial data analysis and validation intercomparisons indicate the qua lity of data from CALIOP meets or exceeds expectations. This paper presents a description of the CALIPSO mission, the CALIOP instrument, an d an initial assessment of on-orbit measurement performance.
Winker, David↗
Lessons Learned from Deploying an Analytical Task Management Database
Defining requirements, missions, technologies, and concepts for space exploration involves multiple levels of organizations, teams of people with complementary skills, and analytical models and simulations. Analytical activities range from filling a To-Be-Determined (TBD) in a requirement to creating animations and simulations of exploration missions. In a program as large as returning to the Moon, there are hundreds of simultaneous analysis activities. A way to manage and integrate efforts of this magnitude is to deploy a centralized database that provides the capability to define tasks, identify resources, describe products, schedule deliveries, and generate a variety of reports. This paper describes a web-accessible task management system and explains the lessons learned during the development and deployment of the database. Through the database, managers and team leaders can define tasks, establish review schedules, assign teams, link tasks to specific requirements, identify products, and link the task data records to external repositories that contain the products. Data filters and spreadsheet export utilities provide a powerful capability to create custom reports. Import utilities provide a means to populate the database from previously filled form files. Within a four month period, a small team analyzed requirements, developed a prototype, conducted multiple system demonstrations, and deployed a working system supporting hundreds of users across the aeros pace community. Open-source technologies and agile software development techniques, applied by a skilled team enabled this impressive achievement. Topics in the paper cover the web application technologies, agile software development, an overview of the system's functions and features, dealing with increasing scope, and deploying new versions of the system.
O'Neil, Daniel A.↗
Method for defect free keyhole plasma arc welding
A plasma arc welding process for welding metal of increased thickness with one pass includes operating the plasma arc welding apparatus at a selected plasma gas flow rate, travel speed and arc current, to form a weld having a penetration ratio to weld height to weld width, and maintaining the penetration ratio at less than 0.74. Parameters for the plasma gas flow rate, travel speed and arc current are adjusted to a steady state condition during a start up period and maintained during the steady state condition to complete a weld. During a terminal stopping period, the travel speed is stopped and instantaneously replaced by filler wire which adds material to fill the keyhole that had been formed by the welding process. Parameters are subsequently adjusted during the stopping period to terminate the weld in a sound manner.
Harwig, Dennis D.↗
Method and apparatus for laminar flow control
A method of installing a compressible insert in an exterior surface of a body is disclosed. There is also disclosed a laminar flow control arrangement that may be produced by such method.
Hunt, James↗
Engineered Carbon Nanotube Materials for High-Q Nanomechanical Resonators
This document represents a presentation offered by the Jet Propulsion Laboratory, with assistance from researchers from Brown University and Northrop Grumman. The presentation took place in Seoul, Korea in July 2003 and attempted to demonstrate the fabrication approach regarding the development of high quality factor (high-Q) mechanical oscillators (in the forms of a tunable nanotube resonator and a nanotube array radio frequency [RF] filter) aimed at signal processing and based on carbon nanotubes. The presentation also addressed parallel efforts to develop both in-plane single nanotube resonators as well as vertical array power devices.
chemical vapor depositions↗
STEREO Mission Design Implementation
STEREO (Solar-TErrestrial RElations Observatory) is the third mission in the Solar Terrestrial Probes program (STP) of the National Aeronautics and Space Administration (NASA) Science Mission Directorate Sun-Earth Connection theme. This paper describes the successful implementation (lunar swingby targeting) of the mission following the first phasing orbit to deployment into the heliocentric mission orbits following the two lunar swingbys. The STEREO Project had to make some interesting trajectory decisions in order to exploit opportunities to image a bright comet and an unusual lunar transit across the Sun.
Guzman, Jose J.↗
MEMS-Based Force-Detected Nuclear Magnetic Resonance (FDNMR) Spectrometer
Nuclear Magnetic Resonance (NMR) spectroscopy allows assignment of molecular structure by acquiring the energy spectrum of nuclear spins in a molecule, and by interpreting the symmetry and positions of resonance lines in the spectrum. As such, NMR has become one of the most versatile and ubiquitous spectroscopic methods. Despite these tremendous successes, NMR experiments suffer from inherent low sensitivity due to the relatively low energy of photons in the radio frequency (rt) region of the electromagnetic spectrum. Here, we describe a high-resolution spectroscopy in samples with diameters in the micron range and below. We have reported design and fabrication of force-detected nuclear magnetic resonance (FDNMR).
force detected nuclear magnetic resonance (FDNMR)↗
Estimating Random Errors Due to Shot Noise in Backscatter Lidar Observations
In this paper, we discuss the estimation of random errors due to shot noise in backscatter lidar observations that use either photomultiplier tube (PMT) or avalanche photodiode (APD) detectors. The statistical characteristics of photodetection are reviewed, and photon count distributions of solar background signals and laser backscatter signals are examined using airborne lidar observations at 532 nm using a photon-counting mode APD. Both distributions appear to be Poisson, indicating that the arrival at the photodetector of photons for these signals is a Poisson stochastic process. For Poisson-distributed signals, a proportional, one-to-one relationship is known to exist between the mean of a distribution and its variance. Although the multiplied photocurrent no longer follows a strict Poisson distribution in analog-mode APD and PMT detectors, the proportionality still exists between the mean and the variance of the multiplied photocurrent. We make use of this relationship by introducing the noise scale factor (NSF), which quantifies the constant of proportionality that exists between the root-mean-square of the random noise in a measurement and the square root of the mean signal. Using the NSF to estimate random errors in lidar measurements due to shot noise provides a significant advantage over the conventional error estimation techniques, in that with the NSF uncertainties can be reliably calculated from/for a single data sample. Methods for evaluating the NSF are presented. Algorithms to compute the NSF are developed for the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) lidar and tested using data from the Lidar In-space Technology Experiment (LITE). OCIS Codes:
Liu, Zhaoyan↗