DOE programs in fire and materials

Diverse laboratory experiments and a review of the most recent dose rate data from operating plants have identified key factors responsible for the increase in shutdown radiation fields at a number of BWRs following implementation of HWC. This information suggests strategies to minimize radiation field increases under HWC and to avoid possible problems during chemical decontamination. The results from corrosion release and activity deposition laboratory experiments, performed under NWC, HWC, and cycling conditions, and the chemistry and structure of films that form under cycling conditions were compiled and reviewed. Operating plant experience under HWC, including the on-line gamma spectroscopy measurements performed at Hope Creek, was also studied. The radiation buildup measurements at Monticello, Brunswick-2, and Duane Arnold were also considered. The focus was to identify those areas that provided a general consensus about the factors responsible for activity buildup under HWC. Once this task was accomplished, the information was used to identity procedures that plant operators could utilize to mitigate undesirable effects

The use of high-performance computing to solve participating media radiative heat transfer problems-results of an NSF workshop

Radiation in participating media is an important transport mechanism in many physical systems. The simulation of complex radiative transfer has not effectively exploited high-performance computing capabilities. In response to this need, a workshop attended by members active in the high-performance computing community, members active in the radiative transfer community, and members from closely related fields was held to identify how high-performance computing can be used effectively to solve the transport equation and advance the state-of-the-art in simulating radiative heat transfer. This workshop was held on March 29-30, 1994 in Albuquerque, New Mexico and was conducted by Sandia National Laboratories. The objectives of this workshop were to provide a vehicle to stimulate interest and new research directions within the two communities to exploit the advantages of high-performance computing for solving complex radiative heat transfer problems that are otherwise intractable

How Low Can the Influence of Meaning Go? Does Activation in the Semantic System Influence Object Detection?

Interacting with the objects we perceive in our environment is an essential aspect of daily life. Therefore, it is important to understand the factors that influence object detection. This dissertation, comprising three chapters, investigated whether object meaning (i.e., semantics) influences object detection. Figure assignment served as the index of object detection in all experiments in all chapters. Masked displays in which a portion of a familiar object was sketched on one side of the central border – the critical or “familiar configuration” side – were shown for either 90 ms or 100 ms; the longer exposure duration allowed more time for the familiar object in the displays to activate semantics. Familiar objects were depicted in both upright and inverted orientations; orientation-dependent detection is expected if configured representations of objects are involved. Chapter 1 investigated whether semantic expectations initiated by words denoting objects influence object detection. An unmasked word was presented before each test display to pre-activate the semantic network; the words denoted either the basic-level (BL) category of the objected sketched on the critical side of the display or an unrelated object from a different superordinate (natural vs. artificial) category (UNRdsc). Detection accuracy and detection RTs from experiments with words were compared to control experiments in which words did not precede test displays. For both 90-ms and 100-ms displays, object detection accuracy was higher than control following BL words but was unaffected by UNRdsc words. In the 100-ms condition, conflict emerged between the semantics activated by the UNR dsc word and the object in the display. Chapter 1 demonstrated that object detection is not only influenced by semantic activation, but it entails semantic activation in that object detection does not occur until conflict within the semantic system is resolved. Chapter 2 investigated whether semantic conflict in our paradigm emerged earlier in time when words in the UNR condition denoted objects in the same superordinate category (UNRssc) as the object sketched in the display. Semantic networks for objects in different superordinate categories have relatively few overlapping properties and are more distant from one another in cognitive and neural space than networks for objects in the same superordinate category. Conflict may emerge earlier in time for displays preceded by UNRssc words because the semantic networks have greater overlap and greater connectivity. Consistent with Chapter 1, object detection accuracy was higher than control for both 90-ms and 100-ms displays following BL words but was unaffected by UNRssc words. As predicted, conflict emerged earlier in time, with 90-ms displays, following UNRssc words. Together, the findings from Chapters 1 and 2 suggest that the amount of conflict in the semantic system at a given point in time varies as a joint function of the amount of semantic activation initiated by the display and the distance in cognitive and neural space between that display-generated semantic activation and the semantic activation initiated by the UNR word. Chapter 3 investigated whether unconsciously presented words affect object detection. BL and UNRdsc words were presented below conscious awareness threshold using sandwich masking in which the briefly presented word was immediately preceded and followed by a string of random letters. Results suggest that semantic activation from unconsciously presented words do not influence object detection. Together, the three chapters broaden our understanding of how, when, and where in the visual hierarchy semantic expectations influence object detection

Semantic Expectation Effects on Object Detection: Using Figure Assignment to Elucidate Mechanisms

Recent evidence suggesting that object detection is improved following valid rather than invalid labels implies that semantics influence object detection. It is not clear, however, whether the results index object detection or feature detection. Further, because control conditions were absent and labels and objects were repeated multiple times, the mechanisms are unknown. We assessed object detection via figure assignment, whereby objects are segmented from backgrounds. Masked bipartite displays depicting a portion of a mono-oriented object (a familiar configuration) on one side of a central border were shown once only for 90 or 100 ms. Familiar configuration is a figural prior. Accurate detection was indexed by reports of an object on the familiar configuration side of the border. Compared to control experiments without labels, valid labels improved accuracy and reduced response times (RTs) more for upright than inverted objects (Studies 1 and 2). Invalid labels denoting different superordinate-level objects (DSC; Study 1) or same superordinate-level objects (SSC; Study 2) reduced accuracy for upright displays only. Orientation dependency indicates that effects are mediated by activated object representations rather than features which are invariant over orientation. Following invalid SSC labels (Study 2), accurate detection RTs were longer than control for both orientations, implicating conflict between semantic representations that had to be resolved before object detection. These results demonstrate that object detection is not just affected by semantics, it entails semantics. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Open access journalThis item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at [email protected]

Radiative Heat Transfer for Emitting, Absorbing and Scattering Planar Media

485 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 1985.This analytical and experimental effort is directed toward understanding and predicting the radiative heat transfer in planar gas and particulate systems. The analysis models both nongray absorption of the gas phase by the exponential wide band model and the redirection of radiant energy by particulate scattering through the optical path length concept. The total hemispherical emittance for a single gas species in an isothermal planar layer with scattering particulate is developed. Exact results for a gas species of H(,2)O or CO(,2) are presented. A factor to incorporate scattering is presented to more easily utilize the analysis. The analysis is also applied to typical combustion processes. The results are given in terms of variables which are known or easily measured.A solution technique is also developed which predicts the radiative heat transfer in a layer having any temperature distribution. The analysis is not restricted to heat transfer, however, and can be applied to radiative transfer for a medium having any internal source distribution. The solution technique predicts the transfer from any single source by solving the photon equation of transfer. Path length distributions are shown for a number of layers and source locations. The technique models isothermal layers very accurately by summing the contributions from a finite number of sources. By weighting the sources appropriately, a nonisothermal layer of particulate is modeled. Results indicate the effect of the cold boundary region on the flux leaving the layer.An experimental system is developed to obtain a hot layer of gas and particulate which flows through a test section with cooled walls. Intrusive probes characterize the medium in terms of particle loading and temperature, and the normally-directed energy emitted from the one dimensional planar medium is measured radiometrically. Gas and particle flow are controlled. An optical system is designed to obtain spectral emittance data from the layer.An experimental investigation is undertaken yielding emittance data from a layer containing carbon dioxide and nitrogen gases, and particulate of BNi-2. Emittance data is presented and exhibits the effects of particulate scattering. An extension of the 4.3 micron carbon dioxide band wings due to scattering is noted. Emittance data for both pure gas and gas and particulate media are compared to analytical predictions.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD

Wind-induced interaction of a large cylindrical calorimeter and an engulfing JP-8 pool fire

As part of a research program in fire science and technology at Sandia National Laboratories (SNL), an experimental and computational investigation of the fire phenomenology associated with the presence of a large (3.66 m diameter), fuselage-sized cylindrical calorimeter engulfed in a large (18.9 m diameter) JP-8 pool fire subjected to high (10.2 m/s) winds were performed. The conditions investigated here resulted in a twofold increase in the incident heat flux to the surface of the object relative to heat fluxes typical of large hydrocarbon fires without engulfed objects. Due to the enhanced fuel/air mixing, enhanced turbulence, and larger flame volume, the highest heat fluxes are observed on the leeward side of the calorimeter. Radiative heat fluxes of 150--250 kW/m{sup 2} on this side, with the maximum heat flux occurring near the top of the calorimeter, were measured. Radiative heat fluxes of 60--200 kW/m{sup 2} were measured on the windward side, with the highest heat flux near the bottom of the calorimeter. Measured and predicted heat fluxes to the pool surface of 25--90 kW/m{sup 2} were observed. The presence of the calorimeter tends to decrease the overall fuel consumption rate primarily due to redirection of the flame zone away from the pool surface. Overall, the numerical models does a reasonable job of representing the essential features of the fire environment but under predicts the heat flux to the calorimeter. These results emphasize the importance of considering the wind-induced interaction of fires and large objects when estimating the incident heat fluxes on a engulfed object. The measurements and analyses are of particular interest since few studies to date have addressed cases where the fire and object are of comparable size