Issue 10 Volume 41 May 16, 2003

PoRTIA, a small CdZnTe balloon instrument that was flown three times in three different shielding configurations. PoRTIA
was passively shielded during its first flight from Palestine, Texas and actively shielded as a piggyback instrument on the GRIS
balloon experiment during its second and third flights from Alice Springs, Australia, using the thick GRIS Nal anticoincidence
shield. A significant CdZnTe background reduction was achieved during the third flight with PoRTIA placed completely inside
the GRIS shield and blocking crystal, and thus completely surrounded by 15 cm of Nal. A unique balloon altitude background
data set is provided by CdZnTe and Ge detectors simultaneously surrounded by the same thick anticoincidence shield; the
presence of a single coxial Ge detector inside the shield next to PoRTIA allowed a measurement of the ambient neutron flux
inside the shield throughout the flight. These neutrons interact with the detector material to produce isomeric states of the Cd,
Zn and Te nuclei that radiatively decay; calculations are presented that indicate that these decays may explain most of the fully
shielded CdZnTe background.
Author
Balloon-Borne Instruments; Gamma Rays; X Rays; Anticoincidence Detectors; Electromagnetic Shielding; Sensitivity
Analysis; Measuring Instruments
20030034606 NASA Glenn Research Center, Cleveland, OH, USA
Effects on Diagnostic Parameters After Removing Additional Synchronous Gear Meshes
Decker, Harry J.; April 2003; 14 pp.; In English; 57th Meeting of the Society for Machinery Failure Prevention Technology
(MFPT), 14-18 Apr. 2003, Virginia Beach, VA, USA; Original contains color illustrations
Contract(s)/Grant(s): WBS-22-708-87-12; DA Proj. 1L1-61102-AF-20
Report No.(s): NASA/TM-2003-212312; NAS 1.15:212312; E-13899; ARL-TR-2933; No Copyright; Avail: CASI; A03,
Hardcopy
Gear cracks are typically difficult to diagnose with sufficient time before catastrophic damage occurs. Significant damage
must be present before algorithms appear to be able to detect the damage. Frequently there are multiple gear meshes on a
single shaft. Since they are all synchronous with the shaft frequency, the commonly used synchronous averaging technique
is ineffective in removing other gear mesh effects. Carefully applying a filter to these extraneous gear mesh frequencies can
reduce the overall vibration signal and increase the accuracy of commonly used vibration metrics. The vibration signals from
three seeded fault tests were analyzed using this filtering procedure. Both the filtered and unfiltered vibration signals were then
analyzed using commonly used fault detection metrics and compared. The tests were conducted on aerospace quality spur
gears in a test rig. The tests were conducted at speeds ranging from 2500 to 5000 revolutions per minute and torques from
184 to 228 percent of design load. The inability to detect these cracks with high confidence results from the high loading which
is causing fast fracture as opposed to stable crack growth. The results indicate that these techniques do not currently produce
an indication of damage that significantly exceeds experimental scatter.
Author
Systems Health Monitoring; Gear Teeth; Fracture Mechanics; Synchronous Motors; Crack Propagation; Grid Generation
(Mathematics)
20030036936 National Inst. of Standards and Technology (CSTL), Gaithersburg, MD
Wear Mechanisms of Valves and Valve Seat Inserts in a Gas-Fired Reciprocating Engine
Lacey, P. I.; Hsu, S. M.; Gates, R. S.; Lee, S.; Ives, L.; Jun. 1990; 80 pp.; In English
Report No.(s): PB2003-101410; NISTIR-90-4264; No Copyright; Avail: CASI; A05, Hardcopy
The objective of the report is to quantitatively measure wear and to identify the dominant wear mechanisms experienced
by selected valve and valve seat insert combinations during operation in a natural gas-fueled reciprocating engine.
NTIS
Valves; Wear Tests; Piston Engines
20030037026 National Renewable Energy Lab., Golden, CO
Durability of Solar Reflective Materials with an Alumina Hard Coat Produced by Ion-Bean-Assisted Deposition
Kennedy, C. E.; Smilgys, R. V.; Oct. 2002; In English
Report No.(s): DE2002-15002207; No Copyright; Avail: National Technical Information Service (NTIS)
A promising low-cost reflector material for solar concentrating power (CSP) generation is a silvered substrate protected
by an alumina coating several microns thick. The alumina hard coat is deposited under high vacuum by ion-beam-assisteddeposition
(IBAD). Samples of this material have been produced both by batch and continuous roll-coating processes. The
substrate materials investigated were polyethylene terephthalate (PET), PET laminated to stainless-steel foil, and chrome-
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