A New Pulse-Modulation Technique for Guidance and Control of Automated Spacecraft
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Automated Spacecraft↗
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A technique for recording sphygmograms of dogs
Pulse technique for recording blood pressure of dogs during space flights - phonocardiography
PULSE↗
Quantum Sensed Electron Spin Resonance Discovery Platform (Final Report)
The properties of materials can change dramatically at the nanoscale new and useful properties can emerge. An example is found in the paramagnetism in iron oxide magnetic nanoparticles. Using magnetically sensitive nitrogen-vacancy centers in diamond, we developed a platform to study electron spin resonance of nanoscale materials. To implement the platform, diamond substrates were prepared with nitrogen vacancy centers near the surface. Nanoparticles were placed on the surface using a drop casting technique. Using optical and microwave pulsing techniques, we demonstrated T1 relaxometry and double electron-electron resonance techniques for measuring the local electron spin resonance. The diamond NV platform developed in this project provides a combination of good magnetic field sensitivity and high spatial resolution and will be used for future investigations of nanomaterials and quantum materials.
36 MATERIALS SCIENCE↗
Pulsed NMR spectroscopy
Method gives results approximating those of classical continuous-irradiation method but in less time. Method also makes it possible to measure chemical shifts and spin-lattice relaxation times with improved sensitivity. Equipment can be used for adiabatic demagnetization experiments, measurements of rotating-frame spin/lattice relaxation times, and accurate measurements of exact resonance points. When measuring relaxation times, pulse technique can be very effective since pulses may be limited in amplitude and length to prevent spin system from being driven into saturation.
Burum, D. P.↗
Pulse Stripping Analysis: A Technique for Determination of Some Metals in Aerosols and Other Limited Size Samples
A technique for determining lead with a detection limit down to a nanogram on limited size samples is described. The technique is an electrochemical one and involves pre-concentration of the metal species in a mercury drop. Although the emphasis in this paper is on the determination of lead, many metal ion species which are reducible to the metal at an electrode are equally determinable. A technique called pulse polarography is proposed to determine the metals in the drop and this technique is discussed and is compared with other techniques. Other approaches for determination of lead are also compared. Some data are also reported for the lead content of Ventura County particulates. The characterization of lead species by solubility parameters is discussed.
Parry, Edward P.↗
Determining Thermal Diffusivities of Radiating Specimens
Two heat-pulse techniques eliminate uncertainties due to radiation losses. Flashlamp supplies pulse of heat to one side of specimen. Temperatures of illumninated surface and of opposite surface monitored photometrically. In second method, pulse of electrons supplies heat to one side of specimen. Temperature of opposite side monitored by photon detector. Techniques needed because radiation heat losses in this temperature range introduce uncertainties into conventional heat-flux measurements.
Wood, C.↗
Characterizing soil water content variability across spatial scales from optimized high-resolution distributed temperature sensing technique
Fiber-optic Distributed Temperature Sensing, when combined with the Single-probe Heat-pulse technique can measure soil moisture (θ) across spatial scales. The key limitation of this system is in obtaining the relationship between soil thermal conductivity (λ) and θ for a specific field. Using the Department of Energy Atmospheric Radiation Measurement (ARM) site, this study tested a new methodology to account for the spatial variability in the λ-θ relationship using a Gaussian processes model. The resulting accurate θ measurements (RMSE = 0.03 m 3 m –3 ) were used to characterize the spatial variability of θ across scales and to develop an empirical equation that can correct for the changes in the θ spatial variability observed at different spatial resolutions. In addition, the number of required samples to accurately characterize θ and its variability over scales ranging from 5 m and 350 m were estimated. Finally, these findings provide key information to scale soil moisture from centimeters to hundreds of meters for process understanding.
54 ENVIRONMENTAL SCIENCES↗
Noninvasive measurement of pulsatile intracranial pressure using ultrasound
The present study was designed to validate our noninvasive ultrasonic technique (pulse phase locked loop: PPLL) for measuring intracranial pressure (ICP) waveforms. The technique is based upon detecting skull movements which are known to occur in conjunction with altered intracranial pressure. In bench model studies, PPLL output was highly correlated with changes in the distance between a transducer and a reflecting target (R2 = 0.977). In cadaver studies, transcranial distance was measured while pulsations of ICP (amplitudes of zero to 10 mmHg) were generated by rhythmic injections of saline. Frequency analyses (fast Fourier transformation) clearly demonstrate the correspondence between the PPLL output and ICP pulse cycles. Although theoretically there is a slight possibility that changes in the PPLL output are caused by changes in the ultrasonic velocity of brain tissue, the decreased amplitudes of the PPLL output as the external compression of the head was increased indicates that the PPLL output represents substantial skull movement associated with altered ICP. In conclusion, the ultrasound device has sufficient sensitivity to detect transcranial pulsations which occur in association with the cardiac cycle. Our technique makes it possible to analyze ICP waveforms noninvasively and will be helpful for understanding intracranial compliance and cerebrovascular circulation.
NASA Center ARC↗
Electrical switching in cadmium boracite single crystals
Cadmium boracite single crystals at high temperatures ( 300 C) were found to exhibit a reversible electric field-induced transition between a highly insulative and a conductive state. The switching threshold is smaller than a few volts for an electrode spacing of a few tenth of a millimeter corresponding to an electric field of 100 to 1000 V/cm. This is much smaller than the dielectric break-down field for an insulator such as boracite. The insulative state reappears after voltage removal. A pulse technique revealed two different types of switching. Unstable switching occurs when the pulse voltage slightly exceeds the switching threshold and is characterized by a pre-switching delay and also a residual current after voltage pulse removal. A stable type of switching occurs when the voltage becomes sufficiently high. Possible device applications of this switching phenomenon are discussed.
Takahashi, T.↗
Aircraft lightning-induced voltage test technique developments
High voltage safety, fuels safety, simulation, and response/measurement techniques are discussed. Travelling wave transit times, return circuit conductor configurations, LC ladder network generators, and repetitive pulse techniques are also discussed. Differential conductive coaxial cable, analog fiber optic link, repetitive pulse sampled data instrumentation system, flash A/D optic link system, and an FM telemetry system are considered.
Crouch, K. E.↗
Directional spectra of ocean waves from microwave backscatter: A physical optics solution with application to the short-pulse and two-frequency measurement techniques
Two simple microwave radar techniques that are potentially capable of providing routine satellite measurements of the directional spectrum of ocean waves were developed. One technique, the short pulse technique, makes use of very short pulses to resolve ocean surface wave contrast features in the range direction; the other technique, the two frequency correlation technique makes use of coherency in the transmitted waveform to detect the large ocean wave contrast modulation as a beat or mixing frequency in the power backscattered at two closely separated microwave frequencies. A frequency domain analysis of the short pulse and two frequency systems shows that the two measurement systems are essentially duals; they each operate on the generalized (three frequency) fourth-order statistical moment of the surface transfer function in different, but symmetrical ways, and they both measure the same directional contrast modulation spectrum. A three dimensional physical optics solution for the fourth-order moment was obtained for backscatter in the near vertical, specular regime, assuming Gaussian surface statistics.
Jackson, F. C.↗
The optical pumping of alkali atoms using coherent radiation from semi-conductor injection lasers and incoherent radiation from resonance lamps
An experimental study for creating population differences in the ground states of alkali atoms (Cesium 133) is presented. Studies made on GaAs-junction lasers and the achievement of population inversions among the hyperfine levels in the ground state of Cs 133 by optically pumping it with radiation from a GaAs diode laser. Laser output was used to monitor the populations in the ground state hyperfine levels as well as to perform the hyperfine pumping. A GaAs laser operated at about 77 K was used to scan the 8521 A line of Cs 133. Experiments were performed both with neon-filled and with paraflint-coated cells containing the cesium vapor. Investigations were also made for the development of the triple resonance coherent pulse technique and for the detection of microwave induced hyperfine trasistions by destroying the phase relationships produced by a radio frequency pulse. A pulsed cesium resonance lamp developed, and the lamp showed clean and reproducible switching characteristics.
Singh, G.↗
Compact, Engineered, 2-Micron Coherent Doppler Wind Lidar Prototype: A New NASA Instrument Incubator Program Project
A new project, selected in 2005 by NASA s Science Mission Directorate (SMD) under the Instrument Incubator Program (IIP), will be described. The 3-year effort is intended to design, fabricate, and demonstrate a packaged, rugged, compact, space-qualifiable coherent Doppler wind lidar (DWL) transceiver capable of future validation in an aircraft and/or Unmanned Aerial Vehicle (UAV). The packaged DWL will utilize the numerous advances in pulsed, solid-state, 2-micron laser technology at NASA s Langley Research Center (LaRC) in such areas as crystal composition, architecture, efficiency, cooling techniques, pulse energy, and beam quality. The extensive experience of Raytheon Space and Airborne Systems (RSAS) in coherent lidar systems, in spacebased sensors, and in packaging rugged lidar systems will be applied to this project. The packaged transceiver will be as close to an envisioned space-based DWL system as the resources and technology readiness allow. We will attempt to facilitate a future upgrade to a coherent lidar system capable of simultaneous wind and CO2 concentration profile measurements. Since aerosol and dust concentration is also available from the lidar signal, the potential for a triple measurement lidar system is attractive for both Earth and Mars remote sensing. A key follow on step after the IIP will be to add a telescope, scanner, and software for aircraft validation. This IIP should also put us in a position to begin a parallel formulation study in the 2006-2007 timeframe for a space-based DWL demonstration mission early next decade.
Kavaya, Michael J.↗
Suppressing The Growth Of Dendrites In Secondary Li Cells
Proposed technique for suppressing growth of lithium dendrites in rechargeable lithium electrochemical power cells involves periodic interruption of steady charging current with short, high-current discharge pulses. Technique applicable to lithium cells of several different types, including Li/TiS(2), Li/NbSe(3), Li/CoO(2), Li/MoS(2), Li/Vo(x), and Li/MnO(2). Cells candidates for use in spacecraft, military, communications, automotive, and other applications in which high-energy-density rechargeable batteries needed.
Davies, Evan D.↗
Alternative signal processing techniques for a pulsed laser Doppler velocimeter system
The laser Doppler velocimeter system (LDV) being tested at NASA MSFC, Alabama, relies on a bank of classical filters for processing the returned lidar signal. Due to the complexity of this conventional filter system, alternative signal processing methods have been proposed for obtaining the Doppler spectrum. The fast Fourier transform (FFT) and the pulse-pair estimator are two techniques which appear to offer some advantages over the existing system. The work reported employs digital computer simulation to compare and evaluate these two processing methods for determining the first and second moments of the LDV velocity spectrum.
Calhoun, M. D.↗
Thermal diffusivity of diamond films
A laser pulse technique to measure the thermal diffusivity of diamond films deposited on a silicon substrate is developed. The effective thermal diffusivity of diamond film on silicon was measured by observing the phase and amplitude of the cyclic thermal waves generated by the laser pulses. An analytical model is developed to calculate the effective in-plane (face-parallel) diffusivity of a two layer system. The model is used to reduce the effective thermal diffusivity of the diamond/silicon sample to a value for the thermal diffusivity and conductivity of the diamond film. Phase and amplitude measurements give similar results. The thermal conductivity of the films is found to be better than that of type 1a natural diamond.
Albin, Sacharia↗
Droplet field visualization and characterization via digital image analysis
This paper describes techniques that have been developed at JPL for visualization and measurements of droplet fields in a moving airstream. The techniques have been applied to a variety of problems which include simulation of heavy rain conditions in a wind tunnel, engine ingestion of wheel spray, analysis of fuel nozzle sprays and aerodynamic breakup of non-Newtonian liquids. The approach pursued here is direct imaging using a pulsed laser illumination source, followed by digital processing of photographic images. A laser double pulse technique has been used for determination of droplet velocities. Laser induced fluorescence has been used to enhance droplet definition in photographic images. The image processing software developed is capable of distinguishing between out-of-focus and in-focus drops, retaining only the latter for size determination.
Hernan, M. A.↗
High temperature measuring device
Ultrasonic pulse technique for measuring average gas temperature in nuclear rocket engine - sound propagation and environmental studies
NUCLEAR ROCKET↗