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48 records · Page 3

Simulation of January 1-7, 1978 events

The solar wind disturbances of January 1 to 7, 1978 are reconstructed by a modeling method. First, the interplanetary magnetic field (IMF) background pattern, including a corotating shock, is reproduced using the Stanford source surface map. Then, two solar flares with their onset times on January 1, 0717 UT at S17 deg E10 deg and 2147 UT S17 deg E32 deg, respectively, are selected to generate two interplanetary transient shocks. It is shown that these two shocks interacted with the corotating shock, resulting in a series of interplanetary events observed by four spacecraft, Helios 1 and 2, IMP-8 (Interplanetary Monitoring Platform 8), and Voyager 2. Results show that these three shock wave interact and coalesce in interplanetary space such that Helios 2 and Voyager 2 observed only one shock and Helios 1 and IMP-8 observed two shocks. All shocks observed by the four spacecraft, except the corotating shock at Helios 1, are either a transient shock or a shock which is formed from coalescing of the transient shocks with the corotating shock. The method is useful in reconstructing a very complicated chain of interplanetary events observed by a number of spacecraft.

Chao, J. K.↗

Oxygen isotopes implanted in the LDEF spacecraft

Depth profiles of O-16 and O-18/O-16 were measured on stainless steel nuts and copper sheet (from a grounding strap) recovered from the leading edge of LDEF (Tray E10). The measurements were obtained by dynamic SIMS (secondary ion mass spectrometry) using a VG Isolab 54 ion microprobe. Plots of O-18/O-16 against time, show large depletions of up to a factor of 2 compared to the O-18/O-16 value at sea level. The O-16 current decreases by 2 orders of magnitude in the interior of the metal, and the corresponding profile of anomalous O-16 is strongly peaked in the outer few tens of nanometers of the surface. This depth scale is a tentative one based on estimated sputtering rates. Plots of O-18/O-16 against 1/O-16 should be linear if two isotopically distinct components, one of variable concentration (orbital component) and one of fixed concentration (normal oxygen), are mixed. Data to be presented at the meeting show departures from linearity which result from variability in the concentration of normal oxygen, but may also arise from the implantation of oxygen with a range of fractionation due to the decaying orbit of the LDEF, sputtering of the surface by atomic oxygen, and the different momenta of the two isotopes due to their equal velocities. The potential for using this method as a means of identifying exposure to low-Earth orbit, de-convoluting the effects of space exposure from terrestrial contamination, and using the implanted anomolous oxygen as a means of studying the atomic oxygen density and upper atmosphere temperature height profile will be discussed at the meeting.

Saxton, J. M.↗

Oxygen isotopes implanted in the LDEF spacecraft

Secondary ion mass spectrometry was used to study oxygen implanted in the surface of copper from the Long Duration Exposure Facility (LDEF). Oxidation that occurred in orbit shows a characteristic oxygen isotope composition, depleted in O-18. The measured depletion is comparable to the predicted depletion (45 percent) based on a model of the gravitational separation of the oxygen isotopes. The anomalous oxygen was contained within 10nm of the surface. Tray E10 was calculated to have received 5.14 x 10(exp 21) atoms of oxygen cm(sup -2) during the LDEF mission and so there is sufficient anomalous implanted oxygen present in the surface to obtain a reliable isotopic profile.

Saxton, J. M.↗

Comparison of Spacecraft Contamination Models with Well-Defined Flight Experiment

During this reporting period, the phase 1 interim report was written and submitted. Detailed computer models were used to predict exposure to atomic oxygen and solar ultraviolet radiation. ESCA survey measurements were started on the tray wall section cut from LDEF tray location EIO-3. At this time there are no technical issues impeding the progress of the required tasks. Cost are in line withn the percentage of completion of tasks. The expended budget is 18% of the total and the project is approximately 18% complete. During the next reporting period we will continue to analyze points from tray locations E10-3 and A4-1 using ESCA and auger surface analysis techniques and a detailed location map will be produced.

Pippin, Gary↗

Initial Results on the Meteoritic Component of new Sediment Cores Containing Deposits of the Eltanin Impact Event

The late Pliocene impact of the Eltanin asteroid is the only known asteroid impact in a deep- ocean (-5 km) basin . This was first discovered in 1981 as an Ir anomaly in sediment cores collected by the USNS Eltanin in 1965. In 1995, Polarstern expedition ANT XII/4 made the first geological survey of the suspected impact region. Three sediment cores sampled around the San Martin seamounts (approx. 57.5 S, 91 W) contained well-preserved impact deposits that include disturbed ocean sediments and meteoritic impact ejecta. The latter is composed of shock-melted asteroidal materials and unmelted meteorites. In 2001, the FS Polarstern returned to the impact area during expedition ANT XVIIU5a. At least 16 cores were recovered that contain ejecta deposits. These cores and geophysical data from the expedition can be used to map the effects of the impact over a region of about 80,000 square km. To date we have measured Ir concentrations in sediments from seven of the new cores and preliminary data should be available for a few more by the time of the meeting. Our initial interpretation of these data is that there is a region in the vicinity of the San Martin Seamounts comprising at least 20,000 square km in which the average amount of meteoritic material deposited was more than 1 g per square cm. This alone is enough material to support a 500 m asteroid. Beyond this is a region of about 60,000 square km, mostly to the north and west, where the amount of ejecta probably averages about 0.2 g per square cm. Another 400 km to the east, USNS Eltanin core E10-2 has about 0.05 g per square cm, so we know that ejecta probably occurs across more than a million square km of ocean floor. A key to future exploration of this impact is to find evidence of the ejecta at more sites distant from the seamounts. We currently have almost no data from regions to the west or south of the San Martin seamounts.

Kyte, Frank T.↗

Precise measurement of the nuclear dependence of the EMC effect in light nuclei

Measurements of inclusive electron scattering cross-section ratios from light nuclei over a wide range of the Björken G (0.3 ? G ? 1) up to &2 = 8.3 GeV2 were made as part of experiment E10-10-008, which was conducted in Hall C at the Thomas Jefferson National Accelerator Facility. The measurements were performed using a beam energy of 10.602 GeV and an average beam current of 45 `A. This dissertation provides a thorough description of the experiment as well as the extracted ratios of inclusive nuclear cross-sections with respect to the deuterium cross-sections (the EMC effect) for the targets 9Be, 12C, 10B, and 11B. The nuclear dependence of the inclusive inelastic electron scattering cross-section has been measured for the first time in 10B and 11B.

Karki, Abishek↗

Biofuels Information Center

The purpose of the Biofuels Information Center (BIC) task is to provide relevant data, information, reports, and web-based tools to all bioenergy stakeholders. The BIC task began in FY08 to meet the requirement under Title II, Sec. 229 of the Energy Independence and Security Act of 2007 (EISA) requires DOE to develop a "Biofuels and Biorefinery Information Center". The BIC task supports biofuels pages content on the EERE's most visited website - the Alternative Fuels Data Center (AFDC http://www.afdc.energy.gov) and the Bioenergy Atlas tools (currently archived) (previous address https://maps.nrel.gov). This task results in more than 1.7 million web pageviews (an instance of an internet user visiting a webpage) per year. In FY22, the task completed the final year of the 5 year USDA Biofuels Infrastructure Partnership (BIP). The USDA BIP expanded infrastructure for E15 and/or E85 to approximately 850 stations and NREL received and reviewed data for quality analyzed all infrastructure and sales data collected by USDA. Stations are privately held and previously it was difficult to ascertain infrastructure and sales data. This unique dataset allows insight into infrastructure data (number of pumps and tanks, costs to install new equipment) and sales data (price and volume for E10, E15, E85, and diesel by month). The 2021 USDA BIP National Summary Report is with DOE for review prior to publication. Future work will include the biannual Bioenergy Industry Status Report (4 previous versions have been published) . The task also supports the principal investigator's time to engage stakeholders on infrastructure and deployment of biofuels. This includes leading, membership, and participation in the following roles: member Board of Advisors at the Fuels Institute, voting member for multiple UL standards committees, Co-Chair of the Infrastructure team at Agriculture/Auto/Ethanol, Member of Coordination Research Council's ULSD Corrosion Committee. The Principal investigator routinely responds to industry inquires to assist in deployment of biofuels regularly.

biofuels↗

FLEX-FUEL MIXING CONTROLLED COMBUSTION ENABLED BY PRECHAMBER IGNITION

There is an imminent need to displace fossil diesel fuel with cleaner burning, domestically produced, renewable fuels for use in heavy-duty engines. Bioethanol is a prime candidate as it widely adopted in the U.S. as a gasoline additive ranging in volume percentage from 10% (E10) up to 85% (E85). Direct substitution of market available ethanol-gasoline blends for diesel fuel is not plausible as the stark reactivity differences would not constitute the same ignition quality nor achieve auto-ignition at all. This work focuses on the development of prechamber enabled mixing-controlled combustion (PC-MCC) as an advanced combustion strategy to facilitate reliable ignition and diffusion style combustion ethanol-gasoline fuel blends. PC-MCC involves integration of an actively fueled prechamber (PC) into a conventional compression ignition combustion system. When ignited, the PC ejects hot turbulent jets into the main combustion chamber that then interact with the direct injected fuel, prompting immediate ignition. The PC jet flames provide a robust thermal ignition source that allows the engine to operate agnostic of fuel composition, or flex-fuel. Computational fluid dynamics (CFD) modeling was used to assess critical design features of the PC while garnering insights into the ignition strategies that facilitate robust performance. A key finding was the ignition performance benefits of fuel-rich PC operation which yield exothermic jets. Based on the numerical findings, a prototype igniter was tested experimentally on both single and multi-cylinder engine platforms at a variety of operating conditions. The experimental results indicate flex-fuel PC-MCC is well capable of diesel-like combustion processes by demonstrating matched or improved gross thermal efficiencies and load variability within 2%. Fuel grade ethanol (E98) exhibited consistently lower NOx and immeasurable soot across the load space. E98 also demonstrated a significant improvement in thermal efficiency at light loads.

Zeman, Jared↗

Alternative Fuels Data Center Fuel Properties Comparison

This chart compares the physical fuel properties and considerations associated with gasoline/E10, low sulfur diesel, biodiesel, propane, compressed natural gas, liquefied natural gas, ethanol, methanol, hydrogen, and electricity for use as vehicle fuels.

47 OTHER INSTRUMENTATION↗

Consumer Guide to Ethanol and Flexible-Fuel Vehicles

Learn how ethanol is used in transportation fuels and about the different ethanol blends you may find at fueling stations. This fact sheet from Energy Saver includes information on the history of ethanol in the United States, what fuel ethanol is, the three categories of ethanol blends, and flex-fuel vehicles.

ethanol, flexible-fuel vehicles, E10, E15, E85, En↗

Alternative Fuels Data Center Fuel Properties Comparison

This chart compares the physical fuel properties and considerations associated with gasoline/E10, low sulfur diesel, biodiesel, renewable diesel, propane, compressed natural gas, liquefied natural gas, ethanol, methanol, hydrogen, and electricity for use as vehicle fuels.

ADVANCED PROPULSION SYSTEMS↗