19,785 research outputs found
Narrative Policy Analysis
This review explores the book All Hell Breaking Loose: The Pentagons View on Climate Change, written by Micheal Klare, highlighting how the US national security offices are viewing and responding to the ominous looming threats posed by climate change
Some studies on the behavior of W-RE thermocouple materials at high temperatures
Bare 0.25 mm diameter W-Re alloy thermoelements (W, W-3% Re, W-5% Re and W-25%) and BeO-insulated W-3% Re and W-25% Re thermoelements were examined for metallurgical, chemical and thermal emf changes after testing for periods up to 1000 hours at temperatures principally in the range 2000 to 2400 K. Environments for the tests consisted of high purity argon, hydrogen, helium or nitrogen gases. Commercially obtained bare-wire thermoelements typically exhibited a shift in their emf-temperature relationship upon initial exposure. The shift was completed by thermally aging the W-3% Re thermoelement for 1 hour and the W-25% Re thermoelement for 2 minutes at 2400 K in argon or hydrogen. Aged thermoelements experienced no appreciable drift with subsequent exposure at 2400 K in the gaseous environments. The chemically doped W3% Re thermoelement retained a small-grained structure for exposure in excess of 50 hours at 2400 K. BeO-insulated thermoelement assemblies showed varied behavior that depended upon the method of exposure. However, when the assemblies were heated in a furnace, no serious material incompatibility problems were found if the materials were given prior thermal treatments. Thermocouples, assembled from aged W-3% Re and W-25% Re thermoelements and degassed sintered BeO insulators, exhibited a drift of only 2 to 3 K during exposure in argon at 2070 K for 1029 hours
The determination of atmospheric temperature profiles from planetary limb radiance profiles
Inverted planetary limb radiance for determining earth atmosphere temperature from orbiting satellit
An investigation of W-3% Re and W-25% Re thermoelements in vacuum, argon and hydrogen Final report
High vacuum, argon, and hydrogen effects on bare wire rhenium thermoelements at high temperature
State-plane trajectories used to observe and control the behavior of a voltage step-up dc-to-dc converter
State-plane analysis techniques are employed to study the voltage step up energy storage dc-to-dc converter. Within this framework, an example converter operating under the influence of a constant on time and a constant frequency controller is examined. Qualitative insight gained through this approach is used to develop a conceptual free running control law for the voltage step up converter which can achieve steady state operation in one on/off cycle of control. Digital computer simulation data is presented to illustrate and verify the theoretical discussions presented
Development and field testing of a Light Aircraft Oil Surveillance System (LAOSS)
An experimental device consisting of a conventional TV camera with a low light level photo image tube and motor driven polarized filter arrangement was constructed to provide a remote means of discriminating the presence of oil on water surfaces. This polarized light filtering system permitted a series of successive, rapid changes between the vertical and horizontal components of reflected polarized skylight and caused the oil based substances to be more easily observed and identified as a flashing image against a relatively static water surface background. This instrument was flight tested, and the results, with targets of opportunity and more systematic test site data, indicate the potential usefulness of this airborne remote sensing instrument
Silicon strain sensors enable pressure measurement at cryogenic temperatures
Miniature pressure transducers with diffused, heavily doped silicon strain-gage sensor elements, operates over a wide temperature range. Small thermal mass combined with close coupling between a metallic diaphragm and sensor elements minimizes sensitivity to temperature transients
Degradation of Fe-Mg silicates in hot CO2 atmospheres: Applications to Venus
Experiments demonstrated that oxidation of ferromagnesian silicates and magnetite occurs when these minerals are heated at 800 C in 1 atmosphere of CO2, under which conditions hematite is thermodynamically stable. The 30 ppm oxygen impurity in CO2 presumably facilitates the oxidation of some of the ferrous iron initially present in the crystal structures of the minerals. Mossbauer spectral measurements reveal, however, that only CO2 degraded olivine and pigeonite is hematite formed as a magnetically ordered phase at ambient temperatures. In orthopyroxene, some of the ferric iron produced by oxidation is present as nanophase hematite which, because it remains superparamagnetic until 4.2 K, must exist as particles less than or equal to 4 nm in diameter. In the calcic pyroxenes much of the oxidized ferrous iron may still remain as structural Fe3(+) in the host silicates. Some ferric iron may also be present as unit cell sized Fe2O3 inclusions in the pyroxenes, or be segregated along cleavage planes, or be coating mineral grains. In these states of aggregation, the Fe2O3 is unidentifiable by x ray diffraction and in low temperature Mossbauer spectra. Applications of this research to the surface of Venus are discussed
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