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Applications of molecular spectroscopy methods to the study of metal dusting corrosion. (open access)

Applications of molecular spectroscopy methods to the study of metal dusting corrosion.

The interrogation of molecular vibrations in crystalline and amorphous solids by Raman and infrared spectroscopy methods can provide a wealth of revealing information concerning the composition, morphology, and spatial distribution of the extant phases. When these measurements are made in situ, such as during processes taking place in extreme environments (e.g., elevated temperature and pressure, oxidizing or reducing), where phases are evolving and/or dissipating, it is also possible to derive kinetic and mechanistic parameters. This paper summarizes the possibilities and limitations involved in using various types of Raman and infrared measurement methods to study metal dusting corrosion. Applications of conventional, microprobe, and imaging molecular spectroscopy approaches are discussed, with examples taken directly from metal dusting investigations. Some perspective is offered concerning the origin of observable condensed matter phonons emanating from the surface films and the carbon particles that accompany carbon dusting on various types of metals and alloys. Concepts for the systematic investigation of carbon dusting chemistry using molecular spectroscopy methods are presented.
Date: March 11, 2002
Creator: Maroni, V. A.
System: The UNT Digital Library
Barriers in developing and using simulation-based decision-support software (open access)

Barriers in developing and using simulation-based decision-support software

The need for proper consideration of energy-related performance aspects during building design has been identified since the energy crises of the 1970s. However, energy performance is still considered in a very small fraction of building projects, mainly because proper consideration is very expensive. It requires the use of computational software tools, which are not easy to learn and are time-consuming to use. Several attempts have been made to facilitate the use of energy simulation tools, but none has brought a significant increase in the consideration of energy performance. Energy related performance criteria are still considered only in a small fraction of buildings and, in most cases, after most of the building design is complete. This paper is focused on the main barriers in properly considering energy-related performance aspects in building decisions, which range from sociopolitical, to technical. The paper includes consideration of issues related to the general interest of the building industry in energy performance and environmental impact, current practice trends, modeling capabilities and performance of tools, compatibility of computational models and availability of data. Finally, a strategy for government-industry collaboration towards removing the barriers is presented, along with the main issues that need to be resolved towards potential implementation.
Date: March 11, 2002
Creator: Papamichael, Konstantinos & Pal, Vineeta
System: The UNT Digital Library
Deflagration Behavior of PBXN-109 and Composition B at High Pressures and Temperatures (open access)

Deflagration Behavior of PBXN-109 and Composition B at High Pressures and Temperatures

We report deflagration rate measurements on PBXN-109 (RDWAVHTPB) and Composition B (RXDTTNThrvax) at pressures from 1,500-100,000 psi (10-700 MPa). This was done with the LLNL High Pressure Strand Burner, in which embedded wires are used to record the time-of-arrival of the burn front in the cylindrical sample as a function of pressure. The propellant samples are 6.4 mm in diameter and 6.4 mm long, with burn wires inserted between samples. Burning on the cylindrical surface is inhibited with an epoxy or polyurethane layer. With this direct measurement we do not have to account for product gas equation of state or heat losses in the system, and the burn wires allow detection of irregular burning. We report deflagration results for PBXN-109 as received, and also after it has been damaged by heating. The burn behavior of pristine PBXN-109 is very regular, and exhibits a reduction in pressure exponent from 1.32 to 0.85 at pressures above 20,000 psi (135 MPa). When PBXN-109 is thermally damaged by heating to 170-180 C, the deflagration rate is increased by more than a factor of 10. This appears to be a physical effect, as the faster burning may be explained by an increase in surface area. …
Date: March 11, 2002
Creator: Maienschein, J L & Wardell, J F
System: The UNT Digital Library
Pressure Measurements in a PBX 9501 Gauged Acceptor When Impacted by a Steel Plate that is Accelerated by a Thermally Cooked Off PBX 9501 Charge (open access)

Pressure Measurements in a PBX 9501 Gauged Acceptor When Impacted by a Steel Plate that is Accelerated by a Thermally Cooked Off PBX 9501 Charge

Measuring the violence of a thermal explosion of a cased explosive is important for evaluating safety issues of explosive devices in fires. A sympathetic initiation scenario was studied here where a 9.0 cm diameter by 2.5 cm thick disc of PBX 9501 donor charge encased in a 304 stainless steel assembly was heated on top and bottom flat surfaces until it thermally exploded. The initial heating rate at the metal/explosive interface was 5 C per minute until it reaches 170 C; then this temperature is held for 35 minutes to allow temperature equilibration to within a few degrees throughout the explosive. The heating resumed at a rate of 1 C per minute until the PBX 9501 donor thermally exploded. A PBX 9501 acceptor charge with carbon resistor and manganin foil pressure gauges inserted at various depths was placed at a 10 cm standoff distance from the donor charge's top steel cover plate. Piezoelectric arrival time pins were placed in front of the acceptor surface to measure the velocity and shape of the impacting plate. The stainless steel cover plate of the donor charge had a nominal velocity of 0.55 {+-} 0.04 mm/{micro}s upon impact and was non-symmetrically warped. The impact …
Date: March 11, 2002
Creator: Forbes, J W; Garcia, F; Urtiew, P A; Vandersall, K S; Greenwood, D W & Tarver, C M
System: The UNT Digital Library
Vitalinks (open access)

Vitalinks

The objectives of the VITALINKS tabletop exercise are to: Raise awareness of infrastructure interdependency issues; Identify and focus on the most important vulnerabilities and restoration priorities resulting from infrastructure disruptions; Examine the resources (people and equipment) required to sustain systems under emergency conditions; Identify and highlight roles, responsibilities, and authorities (including trans-border issues); and Continue to foster a more effective interface among public and private sector service providers and public officials in developing and implementing critical infrastructure protection, mitigation, response, and recovery options.
Date: March 11, 2002
Creator: Baldwin, T. B.
System: The UNT Digital Library