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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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Irregular variations of earth's rotation velocity and action of solar corpuscular streams on the earth's magnetosphere
Irregular variations of earth rotation velocity explained by action of solar corpuscular streams on magnetosphere
A theoretical and experimental investigation of secondary jets in a Mach 6 free stream with emphasis on the structure of the jet and separation ahead of the jet
Secondary jet flow interaction in hypersonic free stream - structure and flow separation ahead of jet
Some theoretical and experimental investigations of self-oscillations of curved panels in a gas stream
Methods of calculating short shells and reinforced shells, and experiments on self-oscillations of cylindrical panels in supersonic gas stream
Steady geomagnetic micropulsations and solar corpuscular streams
Steady geomagnetic micropulsations and solar corpuscular streams
Free-stream interference effects on effectiveness of control jets near the wing tip of a VTOL aircraft model
Free-stream interference effects on effectiveness of control jets near wing tip of VTOL aircraft model
Unsteady stagnation point heat transfer due to arbitrary timewise-variant free stream velocity.
Unsteady incompressible laminar forced convection around stagnation point due to arbitrary timewise- variant free stream velocity, considering skin friction and heat transfer
Diagnosis of an eddy-resolving Atlantic Ocean model simultation in the vicinity of the Gulf Stream. Part I: Potential voracity
Output of an eddy-resolving model of the North Atlantic is diagnosed in the vicinity of the Gulf Stream (GA), using quasigeostrophic potential voracity (QGPV), Ertel's potential voracity (PV), and particle trajectories. Time series of QGPV show strong input of QGPV by the GS in the top 100 m of the model ocean.
Ulysses Composition, Plasma and Magnetic Field Observations of High Speed Solar wind Streams
During 1992-3 as the Ulysses spacecraft passed in and out of the southern high speed solar wind stream, the Solar Wind Ion Spectrometer, SWICS made continuous composition and temperature measurements of all major solar wind ions.
Radar Interferometry Detection of Hinge Line Migration on Rutford Ice Stream and Carlson Inlet, Antarctica
Satellite synthetic-aperture radar (SAR) Interferometry is employed to map the hinge line, or limit of tidal flexing, of Rutford Ice Stream and Carlson Inlet, Antarctica, and detect its migration between 1992 and 1996. The hinge line is mapped using a model fit from an elastic beam theory.
The Distant Tail Behavior During High Speed Solar Wind Streams and Magnetic Storms
We have examined the ISEE-3 distant tail data during three intense (Dst< -100(sub n)T) magnetic storms and have identified the tail response to high speed solar wind streams, interplanetary magnetic clouds, and near-Earth storms. The three storms have a peak Dst ranging from -150 to -220 nT, and occur on Jan. 9, Feb. 4, and Aug. 8, 1993.
Performance Comparison of Data-Derived Symbol Synchronizers in the Presence of Unbalanced Data Streams
This paper compares the performances of two different types of data-derived symbol synchronizers, namely, Filter and Square (FS) and Digital Data Transition Tracking Loop (DTTL), in the presence of unbalanced data streams.
Radar Backscatter Across the Gulf Stream Sea Surface Temperature Front
Ocean backscatter signatures were measured by the Jet Propulsion Laboratory airborne NUSCAT K(sub u)-band scatterometer across the Gulf Stream sea surface temperature front. The measurements were made during the Surface Wave Dynamics Experiment (SWADE) off the coast of Virginia and Maryland in the winter of 1991.
Identification of Solar Wind Stream Interfaces: A Comparison of Ulysses Plasma and Composition Measurements
Measurements of the specific entropy argument of solar wind protons, T/n superscript y-1, reveal that nearly every occurrence of a high-speed stream seen at Ulysses in 1992-3 is characterized by an abrupt interface at its trailing edge.
Observations on the Long-Period Variability of the Gulf Stream Downstream of Cape Hatteras
This paper indicates that topography, Rossby wave dynamics, and eddy/stream interactions, all appear to have a significant role in determining the space-time scales and propagation properties of the long-period response of sea level in the Gulf Stream.
From subsidies to stressors: Positively skewed ecological gradients alter biological responses to nutrients in streams
Abstract Subsidy–stress gradients offer a useful framework for understanding ecological responses to perturbation and may help inform ecological metrics in highly modified systems. Historic, region‐wide shifts from bottomland hardwood forest to row crop agriculture can cause positively skewed impact gradients in alluvial plain ecoregions, resulting in tolerant organisms that typically exhibit a subsidy response (increased abundance in response to environmental stressors) shifting to a stress response (declining abundance at higher concentrations). As a result, observed biological tolerance in modified ecosystems may differ from less modified regions, creating significant challenges for detecting biological responses to restoration efforts. Using the agriculturally dominated Mississippi Alluvial Plain (MAP) ecoregion in Mississippi, USA, as a case study, we tested the hypothesis that macroinvertebrate taxa that typically display a subsidy response to nutrient enrichment in less modified ecoregions (i.e., nutrient‐tolerance) shift to a stress response to increasing nutrients in highly modified watersheds with elevated baseline nutrient conditions (i.e., nutrient intolerance). The abundance and diversity of MAP‐specific intolerant taxa identified with threshold indicator taxa analysis were either unresponsive or exhibited a subsidy response to increasing nutrients in less modified ecoregions in Mississippi with less land alteration and lower nutrient concentrations, but declined at higher concentrations, providing evidence for a stress response to elevated nutrients in the MAP. Additionally, MAP‐specific tolerant and intolerant taxa richness responded to increased nutrients predictably and consistently across space and time within the MAP. However, in MAP streams, elevated specific conductance was predicted to dampen the response of tolerant and intolerant taxa richness to increasing nutrient concentrations, highlighting the importance of considering multistressor interactions when interpreting biological data. Lastly, we demonstrate the efficacy of this approach with sediment bacterial communities characterized with amplicon sequencing, which lack sufficient life history characteristics necessary for the development of multimetric indices. Both macroinvertebrate and bacterial communities responded similarly to increasing nutrient concentrations, suggesting DNA‐based approaches may provide an efficient biological assessment tool for monitoring water quality improvements in highly modified watersheds.
GraphTango: A Hybrid Representation Format for Efficient Streaming Graph Updates and Analysis
Abstract Streaming graph processing performs batched updates and analytics on a time-evolving graph. The underlying representation format of the graph largely determines the throughputs of these updates and analytics phases. Existing representation formats usually employ variations of hash tables or adjacency lists. However, a recent study showed that the adjacency-list-based approaches perform poorly on heavy-tailed graphs, and the hash table-based approaches suffer on short-tailed graphs. We propose GraphTango, a hybrid representation format that provides excellent update and analytics throughput regardless of the graph’s degree distribution. GraphTango dynamically switches among three different formats based on a vertex’s degree: (i) Low-degree vertices store the edges directly with the neighborhood metadata, confining accesses to a single cache line, (2) Medium-degree vertices use adjacency lists, and (3) High-degree vertices use hash tables as well as adjacency lists. In this case, the adjacency list provides fast traversal during the analytics phase, while the hash table provides constant-time lookups during the update phase. We further optimized the performance by designing an open-addressing-based hash table that fully utilizes every fetched cache line. In addition, we developed a thread-local lock-free memory pool that allows fast growing/shrinking of the adjacency lists and hash tables in a multi-threaded environment. We evaluated GraphTango with the help of the SAGA-Bench framework and compared it with four other representation formats: Stinger, Degree-aware Robin Hood Hashing, and two adjacency list-based formats with different workload balancing scheme. On average, GraphTango provides 4.5x higher insertion throughput, 3.2x higher deletion throughput, and 1.1x higher analytics throughput over the next best format. Furthermore, we integrated GraphTango with the state-of-the-art graph processing frameworks DZiG and RisGraph. Compared to the vanilla DZiG and vanilla RisGraph , [ GraphTango + DZiG ] and [ GraphTango + RisGraph ] reduces the average batch processing time by 2.3x and 1.5x, respectively.
Real-time gross actinide monitoring in extreme (10 6 :1) beta-gamma background fluid streams using mini-ATMFDs
Real-time, trace alpha activity monitoring in extreme mixed radiation fields is a well-known challenge in fission product-rich streams containing mixtures of beta-gamma-alpha radiation-emitting isotopes, arising due to the extreme 10 6 :1 ratio of background beta-gamma vs. alpha radiation activity levels. This paper presents results from a novel approach to addressing this challenge, based on Tensioned Metastable Fluid Detector (TMFD) sensing technology. An acoustically driven technique was developed and tested at Purdue University (using dissolved Rn-Po and U-chain alpha emitters), and validated (with dissolved Pu) at Savannah River National Laboratory for real-time monitoring of alpha activity in the 100–10,000 dpm/mL range.