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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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At least 1,261 records · Page 70
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Theoretical mean colors for RR Lyrae variables

A hydrodynamically pulsating 0.6 solar mass model of a typical RR Lyrae variable was studied with a radiation transport-hydrodynamic computer program to predict theoretical T sub 3 and colors at many phases and to find the proper methods for getting mean colors and the consequent mean effective temperatures. The variable Eddington radiation approximation method was used with gray and with multifrequency absorption coefficients to represent the radiation flow in the outer optically thin layers. Comparison between observed and computed B-V colors indicate that these low Z population 2 models are reasonably accurate using King 1A composition opacities. The well known Oke, Giver, and Searle relation between B-V and T sub e reproduced. Mean colors were found by four different averaging methods. The method that gives a mean color and the mean T sub e closest to the nonpulsating model was the separate intensity means of B and V.

Davis, C. G.↗
DOE OSTI2015

Variation of Radiative Properties During Black Carbon Aging. Theoretical and Experimental Intercomparison

A theoretical model is developed to account for black carbon (BC) aging during three major evolution stages, i.e., freshly emitted aggregates, coated particles by soluble materials, and those after further hygroscopic growth. The geometric-optics surface-wave approach is employed to compute BC single-scattering properties at each stage, which are compared with laboratory measurements. Theoretical predictions using input parameters determined from experiments are consistent with measurements in extinction and scattering cross sections for coated BC (within 30 20%) and absorption enhancement from coating (within 15%). The calculated scattering cross sections of fresh BC aggregates are larger than those experimentally measured, because of uncertainties in measurements and calculations. We apply the aging model to compute BC direct radiative forcing (DRF) over the LA Basin using the CalNex 2010 field measurements. Our results demonstrate that accounting for the interactive radiative properties during BC aging is essential in obtaining reliable DRF estimates within a regional context.

He, Cenlin↗
NASA NTRS1992

A geodetic laser radar rangefinder with 10(exp -7) resolution

A novel geodetic laser radar rangefinder (GLRR) unit utilizing a pair of synchronized 10-psec streak camera systems was developed for displacement measurements of the earth's plates. In order to achieve minimum computing error and assure extremely high spatial resolution, an optical pulse registration clock was developed and used to register a fiducial mark on the time scale of the system. Conventional optical rangefinders have been limited to a relative resolution of 10(exp -6) even for short distances. The system to be reported on today has the capability of measuring a 50km range with an accuracy of 4mm corresponding to a relative resolution of 10(exp -7). With a gain of greater than 3 x 10(exp 3), the system has the capability of detecting extremely weak signals on the order of photon counting. This combined with temporal gating makes daytime measurements comparable in signal-to-noise ratio to nighttime viewing. This is useful for measuring faint signals returning over a range of several tens of kilometers. The present ranging system was designed to observe the mutual displacement of geodetic plates and was employed to measure the boundary between the Philippine and Asian geodetic plates that pass beneath the Suruga Bay near Hamamatsu City, Japan. The system has been in operation for over 3 years. In addition, the system has the ability of producing and detecting optical ranging pulses of several wavelengths simultaneously, making this a complete multicolor system. The basic GLRR system consists of a frequency stabilizing crystal, optical clock, YAG laser, KDP doubling crystal, DK*P tripling crystal, two matched streak cameras (A and B), a control computer, and an output/input periscope system.

Mizushima, Y.↗
NASA NTRSDate not supplied

The PACE-MAPP Polarized Ocean Bio-optical Model

The MAPP polarimeter retrieval algorithm, originally developed for the airborne NASA GISS Research Scanning Polarimeter, is being adapted to the PACE observing system to allow for a simultaneous retrieval of aerosol, thin cirrus, and ocean products using both PACE polarimeters and the OCI shortwave infrared channels. Here, we describe the polarized ocean bio-optical model we have developed for PACE-MAPP, which is designed to use a combination of homogenous and coated spheres to more accurately model the absorption and backscattering properties of algal and non-algal particles, and which also includes absorption by colored dissolved organic matter. We first use Lorenz-Mie computations to create lookup tables to accurately and efficiently characterize the optical properties of homogeneous and coated spheres embedded in water for PACE. We then use these lookup tables to develop a bio-optical model that consists of an external mixture of homogeneous (non-algal) and coated (algal) spheres. Lastly, we use the bio-optical model in forward radiative transfer computations to perform inversions of MODIS remote sensing reflectance for a variety of ocean regions. We explore the sensitivity of these inversions to ocean constituent inherent optical properties.

James Allen↗
DOE OSTI2010

2D Spatial Frequency Considerations in Comparing 1D Power Spectral Density Measurements

The frequency footprint of ID and 2D profiling instruments needs to be carefully considered in comparing ID surface roughness spectrum measurements made by different instruments. Contributions from orthogonal direction frequency components can not be neglected. The use of optical profiling instruments is ubiquitous in the measurement of the roughness of optical surfaces. Their ease-of-use and non-contact measurement method found widespread use in the optics industry for measuring the quality of delicate optical surfaces. Computerized digital data acquisition with these instruments allowed for quick and easy calculation of surface roughness statistics, such as root-mean-square (RMS) roughness. The computing power of the desktop computer allowed for the rapid conversion of spatial domain data into the frequency domain, enabling the application of sophisticated signal processing techniques to be applied to the analysis of surface roughness, the most powerful of which is the power spectral density (PSP) function. Application of the PSD function to surface statistics introduced the concept of 'bandwidth-limited' roughness, where the value of the RMS roughness depends critically upon the spatial frequency response of the instrument. Different instruments with different spatial frequency response characteristics give different answers when measuring the same surface.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗
DOE OSTI2015

SULFUR-BEARING MOLECULES IN MASSIVE STAR-FORMING REGIONS: OBSERVATIONS OF OCS, CS, H{sub 2}S, AND SO

We studied the sulfur chemistry of massive star-forming regions through single-dish submillimeter spectroscopy. OCS, O{sup 13}CS, {sup 13}CS, H{sub 2}S, and SO transitions were observed toward a sample of massive star-forming regions with embedded UCH ii or CH ii regions. These sources could be divided into H ii-hot core and H ii-only sources based on their CH{sub 3}CN emission. Our results show that the OCS line of thirteen sources is optically thick, with optical depth ranging from 5 to 16. Column densities of these molecules were computed under LTE conditions. CS column densities were also derived using its optically thin isotopologue {sup 13}CS. H{sub 2}S is likely to be the most abundant gas-phase sulfuretted molecule in hot massive cores. Both the column density and abundance of sulfur-bearing molecules decrease significantly from H ii-hot core to H ii-only sources. Ages derived from hot core models appear to be consistent with star formation theories, suggesting that abundance ratios of [CS]/[SO], [SO]/[OCS], and [OCS]/[CS] could be used as chemical clocks in massive star-forming regions.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS1990

NASA/MSFC Large Space Structures Ground Test Facility

The NASA/MFSC Large Space Structures Ground Test Facility (LSS GTF) is described in terms of the testing, evaluation, and implementation of control and system identification techniques for typical large space structures. The GTF comprises Control, Astrophysics, and Structures Experiment in Space (CASES) GTF which is being developed and the operational Single Structure Control (SSC) laboratory (an LSS flexible beam suspended vertically with sensor and actuator systems, a real-time computer system, a disturbance system, and an optical pointing system). The configuration of the laboratory and the systems used are set forth in terms of monitoring simulated disturbances. The Shuttle-based CASES experiment involves a 105-foot boom as part of an X-ray experiment, and the control of this structure will be tested at the CASES GTF. The actuation, measurement, sensor, and computer systems are described, and the configuration of the GTF is given.

Jones, Victoria L.↗
DOE OSTI2017

Efficient Fresnel zoneplate pattern data preparation for high-resolution nanofabrication

A Fresnel zoneplate is a diffractive optical element consisting of concentric rings (zones) for which the transmitted light produces a focal spot that is used in all wavelength regimes, including X-rays. The pattern of transmission openings determines the location of the spot and the sub-half wavelength size of the openings can adjust the intensity. Today, very general transmission zoneplate patterns are used for many special imaging and image compensation purposes. Manufacturing zoneplates require a zoneplate pattern file, which precisely describes the size, shape, and contour of the rings based on the desired optical properties of the lens. Generating such a pattern requires the delicate balance of achieving the required optical performance while maintaining manageable file sizes and computation times. Here we describe a new algorithm meeting these needs. In conclusion, by precisely controlling the number of shapes in each zone, the algorithm simultaneously optimizes the desired optical tolerances with the pattern file size.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

A Dynamically-Reconfigurable Burst-Mode Link Using a Nanosecond Photonic Switch

Fast optical circuit switching has great potential to solve scaling issues with traditional packet-switch based networks and improve bandwidth and power efficiency in datacenter and high-performance computing applications. One difficultly in utilizing a fast optical switch is that the optical signal must be rapidly reacquired after each switching event so as to not significantly impact the overall throughput of the system. In this work we present a system-level integration of a nanosecond-scale $2 \times 2$ silicon photonic switch with a 25-Gbps burst-mode receiver that can lock in 31 ns. A novel FPGA-based control plane was used to generate test data, control the silicon photonic switch and burst-mode receiver, and measure bit errors at 12.5 and 20 Gbps. Error-free links (BER $< 10^{-12}$ ) with system-level reconfiguration times below 60 ns (at 20 Gbps) and 90 ns (at 12.5 Gbps) including bit- and frame-synchronization are demonstrated.

32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATI↗
DOE OSTI2020

Flexspander: augmenting expander networks in high-performance systems with optical bandwidth steering

Communication efficiency is one of the deciding factors in determining many of today’s high-performance computing (HPC) applications. Traditionally, HPC systems have been on static network topologies, making them inflexible to the variety of skewed traffic demands that may arise due to the spatial locality inherent in many applications. To handle traffic locality, researchers have proposed integrating optical circuit switches (OCSs) into the network architecture, which reconfigures the network topology to alter and dynamically adapt to the predicted traffic. In this paper, we present a novel reconfigurable network topology called Flexspander. Beyond offering a flexible interconnect, Flexspander also offers full flexibility in terms of construction and can be built with any arbitrary combination of commercial electrical packet switches and OCSs. We evaluate Flexspander performance through extensive simulations with multiple network traces, and our results show improved performance for Flexspander over currently proposed static and reconfigurable topologies in terms of the flow completion time.

Teh, Min Yee↗
DOE OSTI2013

DETERMINING HEATING RATES IN RECONNECTION FORMED FLARE LOOPS OF THE M8.0 FLARE ON 2005 MAY 13

We analyze and model an M8.0 flare on 2005 May 13 observed by the Transition Region and Coronal Explorer and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) to determine the energy release rate from magnetic reconnection that forms and heats numerous flare loops. The flare exhibits two ribbons in UV 1600 A emission. Analysis shows that the UV light curve at each flaring pixel rises impulsively within a few minutes, and decays slowly with a timescale longer than 10 minutes. Since the lower atmosphere (the transition region and chromosphere) responds to energy deposit nearly instantaneously, the rapid UV brightening is thought to reflect the energy release process in the newly formed flare loop rooted at the footpoint. In this paper, we utilize the spatially resolved (down to 1'') UV light curves and the thick-target hard X-ray emission to construct heating functions of a few thousand flare loops anchored at the UV footpoints, and compute plasma evolution in these loops using the enthalpy-based thermal evolution of loops model. The modeled coronal temperatures and densities of these flare loops are then used to calculate coronal radiation. The computed soft X-ray spectra and light curves compare favorably with those observed by RHESSI and by the Geostationary Operational Environmental Satellite X-ray Sensor. The time-dependent transition region differential emission measure for each loop during its decay phase is also computed with a simplified model and used to calculate the optically thin C IV line emission, which dominates the UV 1600 A bandpass during the flare. The computed C IV line emission decays at the same rate as observed. This study presents a method to constrain heating of reconnection-formed flare loops using all available observables independently, and provides insight into the physics of energy release and plasma heating during the flare. With this method, the lower limit of the total energy used to heat the flare loops in this event is estimated to be 1.22 Multiplication-Sign 10{sup 31} erg, of which only 1.9 Multiplication-Sign 10{sup 30} erg is carried by beam-driven upflows during the impulsive phase, suggesting that the coronal plasmas are predominantly heated in situ.

79 ASTRONOMY AND ASTROPHYSICS↗
DOE OSTI2024

Light-induced microwave noise in superconducting microwave-optical transducers

Microwave-to-optical transducers are integral to the future of superconducting quantum computing, as they would enable scaling and long-distance communication of superconducting quantum processors through optical-fiber links. However, optically induced microwave noise poses a significant challenge in achieving quantum transduction between microwave and optical frequencies. In this work, we study light-induced microwave noise in an integrated electro-optical transducer harnessing the Pockels effect of thin-film lithium niobate. We reveal three sources of added noise with distinctive time constants ranging from sub-100 ns to milliseconds. Furthermore, our results provide insights into the mechanisms and corresponding mitigation strategies for light-induced microwave noise in superconducting microwave-optical transducers and pave the way toward realizing the ultimate goal of quantum transduction.

42 ENGINEERING↗
DOE OSTI2018

Embedded 100 Gbps Photonic Components

This innovation to fiber optic component technology increases the performance, reduces the size and reduces the power consumption of optical communications within dense network systems, such as advanced distributed computing systems and data centers. VCSEL technology is enabling short-reach (< 100 m) and >100 Gbps optical interconnections over multi-mode fiber in commercial applications.

42 ENGINEERING↗
NASA NTRS1980

Intercommunications in Real Time, Redundant, Distributed Computer System

An investigation into the applicability of fiber optic communication techniques to real time avionic control systems, in particular the total automatic flight control system used for the VSTOL aircraft is presented. The system consists of spatially distributed microprocessors. The overall control function is partitioned to yield a unidirectional data flow between the processing elements (PE). System reliability is enhanced by the use of triple redundancy. Some general overall system specifications are listed here to provide the necessary background for the requirements of the communications system.

Zanger, H.↗
NASA NTRS1979

Laser Research

Eastman Kodak Company, Rochester, New York is a broad-based firm which produces photographic apparatus and supplies, fibers, chemicals and vitamin concentrates. Much of the company's research and development effort is devoted to photographic science and imaging technology, including laser technology. Eastman Kodak is using a COSMIC computer program called LACOMA in the analysis of laser optical systems and camera design studies. The company reports that use of the program has provided development time savings and reduced computer service fees.

Source record↗
DOE OSTI2022

A wide-field micro-computed tomography detector: micron resolution at half-centimetre scale

Ideal three-dimensional imaging of complex samples made up of micron-scale structures extending over mm to cm, such as biological tissues, requires both wide field of view and high resolution. For existing optics and detectors used for micro-CT (computed tomography) imaging, sub-micron pixel resolution can only be achieved for fields of view of <2 mm. This article presents a unique detector system with a 6 mm field-of-view image circle and 0.5 µm pixel size that can be used in micro-CT units utilizing both synchrotron and commercial X-ray sources. A resolution-test pattern with linear microstructures and whole adult Daphnia magna were imaged at beamline 8.3.2 of the Berkeley Advanced Light Source. Volumes of 10000 × 10000 × 7096 isotropic 0.5 µm voxels were reconstructed over a 5.0 mm × 3.5 mm field of view. Measurements in the projection domain confirmed a 0.90 µm measured spatial resolution that is largely Nyquist-limited. This unprecedented combination of field of view and resolution dramatically reduces the need for sectional scans and computational stitching for large samples, ultimately offering the means to elucidate changes in tissue and cellular morphology in the context of larger, whole, intact model organisms and specimens. This system is also anticipated to benefit micro-CT imaging in materials science, microelectronics, agricultural science and biomedical engineering.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗