Mitre Corporation

About: Mitre Corporation is a company organization based out in Bedford, Massachusetts, United States. It is known for research contribution in the topics: Air traffic control & National Airspace System. The organization has 4884 authors who have published 6053 publications receiving 124808 citations. The organization is also known as: Mitre & MITRE.

The many origins of natural gas

Abstract: Thermodynamic calculations for the C-O-S-H system indicate that at a fixed oxygen fugacity methane is in a stable phase relative to carbon dioxide at high pressures and low temperatures. At a constant temperature and pressure, methane is favored at low oxygen fugacities. Volcanic gases and near-surface igneous rocks exhibit high values of oxygen fugacity. However, direct measurement of the oxygen fugacity of spinels from peridotites of deep origin indicate that the oxygen fugacity of these rocks is low, corresponding to an iron - wustite buffer. The relative abundance of the carbon isotopes C12 and C13 varies widely in natural gases. Methane formed by bacterial fermentation is highly enriched in the lighter isotope, while methane from deep deposits is much less so as is the methane flowing from hydrothermal vents on the East Pacific Rise. Except In extreme cases, the carbon isotope ratio cannot be used alone to assess whether methane is biogenic or abiogenic. The carbon isotope ratio in coexisting methane and carbon dioxide can be used to estimate the temperature at which the two gases came into isotopic equilibrium. This ratio indicates a high temperature of equilibration for a number of gas deposits. The carbon and helium isotope ratios together with their geologic settings are strongly suggestive that the large quantities of methane in Lake Kivu and the gases venting along the East Pacific Rise are abiogenic. Methane associated with the Red Sea brines and various geothermal areas may also be in part abiogenic. The high abundance of carbon in the Sun, the atmosphere of the outer planets, carbonaceous chondrites and comets, suggests that carbon may be more abundant in the Earth than it is in near-surface igneous rocks. Such a high abundance could lead to a progressive outgassing of methane at depth, which then is oxidized near the surface or in the atmosphere. Methane hydrates are stable at low temperatures and high pressures. Today, methane hydrates are found in areas of permafrost and in ocean sediments. Methane hydrates in ocean sediments were first formed about 20 mya (million years ago) when the Antarctic ice sheet reached sea level. Terrestrial methane hydrates formed more recently during the glaciations beginning 1.6 mya. Methane hydrates and trapped gas are probably abundant under the Antarctic ice sheet. The formation of methane hydrates may be related to the low values of carbon dioxide in the atmosphere some 20,000 years ago.

Triple band GPS trap-loaded inverted L antenna array

Abstract: The antenna includes four elements excited with equal amplitudes but with a relative phase difference of 0°, −90°, −180°, and −270°. Each element includes a vertical and horizontal portion. An RF trap filter is located within the horizontal portion so that the antenna provides good gain coverage at all three frequency bands of a modernized global positioning system.

Some invariant properties of the polarization scattering matrix

Abstract: A set of parameters can be based on properties of the polarization scattering matrix which are invariant to change in the axial ratio of the polarization ellipse for the measuring antenna, or to rotation of the antenna about the line of sight. These invariant quantities have the advantage that they are free of the effects of Faraday rotation and of certain errors in antenna polarization, yet depend upon the nature of the scattering body and as such can be used to classify certain characteristics of the body. Some of the parameters of special representations for the scattering matrix, such as the null polarization and eigenpolarization, are simply related to the invariant quantities. However, not all of the significant characteristics of the scattering matrix can be specified in terms of invariant quantities, since two degrees of freedom are necessary, one to account for the axial ratio of measuring antenna and one to account for the relative orientation of the antenna and scatterer about the line of sight. The decomposition of these effects into the product of a rotation operator and an ellipticity operator offers a convenient method for critical examination of polarization dependent characteristics.

Performance Evaluations of the New GPS L5 and L2 Civil (L2C) Signals

Abstract: The United States is planning to implement two new civil signals on the GPS satellites in the next few years. The L2 civil (L2C) signal will be implemented beginning with the first Block IIR-M satellite, anticipated to be launched in 2004. The L5 signal will be implemented beginning with the first Block IIF satellite, anticipated to be launched in 2006. Both new civil signals include design features that make them very different from the only existing civil GPS signal—the L1 C/A-code. In a previous paper, signal structure, cross-correlation protection, tracking loop performance, and multipath were evaluated for each signal. This paper presents additional performance evaluations, such as proposed methods of code acquisition, and receiver tracking thresholds considering platform dynamics and receiver oscillator phase noise. The performance trade-offs between carrier loop bandwidth and loop update time, as well as data demodulation performance, are also evaluated.

Should Chloral Hydrate Be Banned

Abstract: Objective. Current federal regulations of potentially carcinogenic environmental chemicals are based on the assumption that risks for humans can be extrapolated from the effects of chronic high-dose exposure of rodents. It is assumed that all chemicals induce cancer by a genotoxic mechanism (direct interaction with DNA) and that humans metabolize chemicals by the same pathways as the test rodents. Trichloroethylene, a former medicine, is now regulated because of rodent studies. Its major metabolite, chloral hydrate, widely used as a sedative in both adults and children, is in danger of being banned by comparable studies. This paper assesses the safety of chloral hydrate. Design. Analysis of the literature regarding the metabolic, toxicologic, and epidemiologic data on trichloroethylene and chloral hydrate. Results. The dose-response relationship for carcinogenesis of chioral hydrate and other chemicals in its metabolic breakdown pathway is nonlinear in rodents: very high doses given chronically, sufficient to cause cellular necrosis, are necessary for induction of malignancies. In addition, epidemiologic data on people exposed to substantial amounts of trichloroethylene (which is metabolized to chloral hydrate) show no increase in mortality or cancers. Conclusions. The assumptions underlying current regulatory practices for environmental chemicals are not applicable to the medicinal use of chloral hydrate. Instead, a threshold model is appropriate. The data do not suggest the need to ban chloral hydrate as a medicine; however, possible modifications in its use are suggested.