11 research outputs found
Insoluble Coatings for Stirling Engine Heat Pipe Condenser Surfaces
The principal objective of this Phase 2 SBIR program was to develop and demonstrate a practically insoluble coating for nickel-based superalloys for Stirling engine heat pipe applications. Specific technical objectives of the program were: (1) Determine the solubility corrosion rates for Nickel 200, Inconel 718, and Udimet 72OLI in a simulated Stirling engine heat pipe environment, (2) Develop coating processes and techniques for capillary groove and screen wick structures, (3) Evaluate the durability and solubility corrosion rates for capillary groove and screen wick structures coated with an insoluble coating in cylindrical heat pipes operating under Stirling engine conditions, and (4) Design and fabricate a coated full-scale, partial segment of the current Stirling engine heat pipe for the Stirling Space Power Convertor program. The work effort successfully demonstrated a two-step nickel aluminide coating process for groove wick structures and interior wall surfaces in contact with liquid metals; demonstrated a one-step nickel aluminide coating process for nickel screen wick structures; and developed and demonstrated a two-step aluminum-to-nickel aluminide coating process for nickel screen wick structures. In addition, the full-scale, partial segment was fabricated and the interior surfaces and wick structures were coated. The heat pipe was charged with sodium, processed, and scheduled to be life tested for up to ten years as a Phase 3 effort
An Overview of Long Duration Sodium Heat Pipe Tests
High temperature heat pipes are being evaluated for use in energy conversion applications such as fuel cells, gas turbine re-combustors, and Stirling cycle heat sources; with the resurgence of space nuclear power, additional applications include reactor heat removal elements and radiator elements. Long operating life and reliable performance are critical requirements for these applications. Accordingly long-term materials compatibility is being evaluated through the use of high temperature life test heat pipes. Thermacore International, Inc., has carried out several sodium heat pipe life tests to establish long term operating reliability. Four sodium heat pipes have recently demonstrated favorable materials compatibility and heat transport characteristics at high operating temperatures in air over long time periods. A 3l6L stainless steel heat pipe with a sintered porous nickel wick structure and an integral brazed cartridge heater has successfully operated at 650 to 700 C for over 115,000 hours without signs of failure. A second 3l6L stainless steel heat pipe with a specially-designed Inconel 60 I rupture disk and a sintered nickel powder wick has demonstrated over 83,000 hours at 600 to 650 C with similar success. A representative one-tenth segment Stirling Space Power Converter heat pipe with an Inconel 718 envelope and a stainless steel screen wick has operated for over 41 ,000 hours at nearly 700 0c. A hybrid (i.e. gas-fired and solar) heat pipe with a Haynes 230 envelope and a sintered porous nickel wick structure was operated for about 20,000 hours at nearly 700 C without signs of degradation. These life test results collectively have demonstrated the potential for high temperature heat pipes to serve as reliable energy conversion system components for power applications that require long operating lifetime with high reliability, Detailed design specifications, operating hi story, and test results are described for each of these sodium heat pipes. Lessons learned and future life test plans are also discussed
Unravelling the phylogenetic relationships of lichenised fungi in Dothideomyceta
We present a revised phylogeny of lichenised Dothideomyceta
(Arthoniomycetes and Dothideomycetes) based on a combined
data set of nuclear large subunit (nuLSU) and mitochondrial small subunit
(mtSSU) rDNA data. Dothideomyceta is supported as monophyletic with
monophyletic classes Arthoniomycetes and Dothideomycetes;
the latter, however, lacking support in this study. The phylogeny of
lichenised Arthoniomycetes supports the current division into three
families: Chrysothrichaceae (Chrysothrix),
Arthoniaceae (Arthonia s. l., Cryptothecia,
Herpothallon), and Roccellaceae (Chiodecton, Combea,
Dendrographa, Dichosporidium, Enterographa, Erythrodecton, Lecanactis,
Opegrapha, Roccella, Roccellographa, Schismatomma, Simonyella). The
widespread and common Arthonia caesia is strongly supported as a
(non-pigmented) member of Chrysothrix. Monoblastiaceae, Strigulaceae,
and Trypetheliaceae are recovered as unrelated, monophyletic clades
within Dothideomycetes. Also, the genera Arthopyrenia
(Arthopyreniaceae) and Cystocoleus and Racodium
(Capnodiales) are confirmed as Dothideomycetes but unrelated
to each other. Mycomicrothelia is shown to be unrelated to
Arthopyrenia s.str., but is supported as a monophyletic clade sister
to Trypetheliaceae, which is supported by hamathecium characters. The
generic concept in several groups is in need of revision, as indicated by
non-monophyly of genera, such as Arthonia, Astrothelium, Cryptothecia,
Cryptothelium, Enterographa, Opegrapha, and Trypethelium in our
analyses
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Spall experiments in convergent geometry using the atlas pulsed power facility.
{sm_bullet}Four spall experiments have been performed using Atlas {sm_bullet} Purpose was to investigate damage in convergent geometry {sm_bullet} Impact pressures ranged between 45 kbars - 110 kbars {sm_bullet} Diagnostics included VISAR and axial and radial radiographs {sm_bullet} Targets were recovered for post-metallugical analysi
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Material science experiments on the Atlas Facility
Three material properties experiments that are to be performed on the Atlas pulsed power facility are described; friction at sliding metal interfaces, spallation and damage in convergent geomety, and plastic flow at high strain and high strain rate. Construction of this facility has been completed and experiments in high energy density hydrodynamics and material dynamics will begin in 2001
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Comparative Effects of Therapy With Captopril and Digoxin in Patients With Mild to Moderate Heart Failure
This multicenter, double-blind, placebo-controlled study compares the effects of captopril treatment with those of digoxin treatment during maintenance diuretic therapy in patients with mild to moderate heart failure. Compared with placebo, captopril therapy resulted in significantly improved exercise time (mean increase, 82 s vs 35 s) and improved New York Heart Association class (41% vs 22%), but digoxin therapy did not. Digoxin treatment increased ejection fraction (4.4% increase) compared with captopril therapy (1.8% increase) and placebo (0.9% increase). The number of ventricular premature beats decreased 45% in the captopril group and increased 4% in the digoxin group in patients with more than ten ventricular premature beats per hour. Treatment failures, increased requirements for diuretic therapy, and hospitalizations were significantly more frequent in patients receiving placebo compared with those receiving either active drug. Transitory hypotension occurred more frequently with administration of captopril. Captopril treatment is significantly more effective than placebo and is an alternative to digoxin therapy in patients with mild to moderate heart failure who are receiving diuretic maintenance therapy.(JAMA 1988;259:539-544