Coherent Thermal Emission from Photonic Nanostructures Composed of TA, W, GE, and HFO2 Thin Films

Combining an understanding of thin films and structure/property relationships, photonic nano-structures were developed in order to affect the spectral and directional radiative properties of coherent thermal emission. The targeted emission range was 2-20 micrometer. Structures with appropriate materials in order to achieve thermal stability were designed and tested. Implementing a Finite Difference Time Domain numerical method, four truncated multilayer resonators were designed to selectively emit at certain transmissive wavelength bands of the atmosphere in 2-20 micrometer. Ellipsometric measurements and models were used in order to extract the optical constants of thin layers of materials chosen for the resonator designs. These values showed significant disagreement with bulk values found in literature and were used to make more accurate theoretical predictions. A Direct Current Magnetron Sputtering technique was used to fabricate the four resonators, W-Ge-W, W-HfO2-W, Ta-Ge-Ta, and Ta-HfO2-Ta, with layer thicknesses of 10-760-145 nm, 10-701-145 nm, 9.6-728-169 nm, and 9.6-301-169 nm, respectively. Reflectance measurements were taken at room temperature and various high temperatures to investigate the thermal stability of the spectral reflectance of the structures. From these reflectance measurements, the W-Ge-W and Ta-Ge-Ta designs proved to hold up the best at higher temperatures

Which Way Is Which? Examining Global/Local Processing With Symbolic Cues

A new method combining spatial-cueing and compound-stimulus paradigms draws on involuntary attentional orienting elicited by a spatially uninformative central arrow cue to investigate global/local processing under incidental processing conditions, wherein global/local levels were uninformative (do not aid performance) and task-irrelevant (need not be processed to perform the task). The task was peripheral target detection. Cues were compound arrows, which were either consistent (global/local arrows oriented in same direction) or inconsistent (global/local arrows oriented in opposite directions). Global/local processing was measured by spatial-cueing effects (response time [RT] difference between target locations validly cued by an arrow and targets at different locations), with the test of global/local advantage represented by the effect of cue-level for inconsistent cues (RT difference between global-valid and local-valid cues). Cue-target interval (stimulus-onset-asynchrony [SOA]) was manipulated to test whether global/local advantage varied with relative stimulus availability. Experiment 1 observed a Cue-Level × SOA interaction such that an early, large global cueing effect was followed by a later, smaller local cueing effect, indicative of a global-to-local shift in advantage. This occurred despite knowledge that global/local arrows were uninformative and task-irrelevant and could therefore be ignored, thus displaying key properties of an involuntary process. Experiment 2 added neutral cues (arrow at one level, rectangle at the other) and determined that the reversal was not due to inhibition of the globally cued location or to attenuation of global information but rather to the presence of conflicting spatial information. Experiments 3 and 4 ruled out alternative accounts for these results. These data indicate global precedence in attended but incidentally processed objects

Minority electron transport in InP/InGaAs heterojunction bipolar transistors

Electron transport across the base of InP/InGaAs heterojunction bipolar transistors is examined by Monte Carlo simulation. The base transit times and electron distribution functions are examined as a function of basewidth. Clear ballistic behavior is observed only for extremely thin bases (much less than 100 A). Over the range of basewidths of interest for devices, base transport appears diffusive, but the electrons are very far from thermal equilibrium. The diffusive behavior is shown to arise from the sensitivity of the steady-state carrier population to small amounts of large-angle scattering

Which way is which? Examining symbolic control of attention with compound arrow cues

Spatial symbols can generate attentional biases toward peripheral locations compatible with the symbol’s meaning. An important question concerns how one symbol is selected when competing symbols are present. Studies examining this issue for spatially distinct symbols have suggested that selection depends on the task goals. In the present study, we examined whether the influence of competing symbolic stimuli (arrows) at different levels of structure on attentional control also depends on the task goals. Participants made simple detection responses to a peripheral target preceded by a spatially uninformative compound arrow (global arrow composed of local arrows). In addition, participants were required to perform a secondary task in which they matched the orientation of the global arrow (global task) or the location of a uniquely colored local arrow (local task) to a test display presented immediately following a detection response. When the global and local arrows pointed at opposite locations, a local cueing effect emerged in the local task, and a global cueing effect in the global task, indicating that the task goals influenced the selection of the level of structure. However, when the local level was spatially neutral (global arrow, local rectangles), a cueing effect was observed independent of task, and when the global level was spatially neutral (global rectangle, local arrows), a cueing effect was observed in the local task only, suggesting that global processing was obligatory and local processing optional. These findings suggest that attentional effects triggered by the global level are more strongly reflexive than those triggered by the local level

Collective excitations of atomic Bose-Einstein condensates

We apply linear-response analysis of the Gross-Pitaevskii equation to obtain the excitation frequencies of a Bose-Einstein condensate confined in a time-averaged orbiting potential trap. Our calculated values are in excellent agreement with those observed in a recent experiment.Comment: 11 pages, 2 Postscript figures, uses psbox.tex for automatic figure inclusion. More info at http://amo.phy.gasou.edu/bec.htm

Human classifier: Observers can deduce task solely from eye movements

Computer classifiers have been successful at classifying various tasks using eye movement statistics. However, the question of human classification of task from eye movements has rarely been studied. Across two experiments, we examined whether humans could classify task based solely on the eye movements of other individuals. In Experiment 1, human classifiers were shown one of three sets of eye movements: Fixations, which were displayed as blue circles, with larger circles meaning longer fixation durations; Scanpaths, which were displayed as yellow arrows; and Videos, in which a neon green dot moved around the screen. There was an additional Scene manipulation in which eye movement properties were displayed either on the original scene where the task (Search, Memory, or Rating) was performed or on a black background in which no scene information was available. Experiment 2 used similar methods but only displayed Fixations and Videos with the same Scene manipulation. The results of both experiments showed successful classification of Search. Interestingly, Search was best classified in the absence of the original scene, particularly in the Fixation condition. Memory also was classified above chance with the strongest classification occurring with Videos in the presence of the scene. Additional analyses on the pattern of correct responses in these two conditions demonstrated which eye movement properties successful classifiers were using. These findings demonstrate conditions under which humans can extract information from eye movement characteristics in addition to providing insight into the relative success/failure of previous computer classifiers

The Spitzer Science Center: using metrics analysis to improve system stability

The Spitzer Science Center (SSC) Software Science Operations System (SOS) is a large, complex software system. Over 1.2 million lines of code had been written for the SOS by time of launch (August 2003). The SSC uses a defect tracking tool called GNATS to enter defect reports and change requests. GNATS has been useful beyond just tracking defects to closure. Prior to launch a number of charts and graphs were generated using metrics collected from GNATS. These reports demonstrated trends and snapshots of the state of the SOS and enabled the SSC to better identify risks to the SOS and focus testing efforts. This paper will focus primarily on the time period of Spitzer's launch and In Orbit Checkout. It will discuss the metrics collected, the analyses done, the format the analyses was presented in, and lessons learned. This work was performed at the California Institute of Technology under contract to the National Aeronautics and Space Administration

Advanced load-testing techniques for a science archive

Performance goals for data archive systems need to be established early in the design process to ensure stability and acceptable response throughput. Load testing is one technique used to measure the progress towards these performance goals. Providing resources for load-test planning is critical, and this planning must include feasibility studies, tool analyses, and generation of an overall load-test strategy. This strategy is much different for science data archives than other systems, including commercial websites and high-volume data centers. This paper will provide an overview of the load testing performed on the Spitzer Space Telescope's science archive, which is part of Science Operations System at the Spitzer Science Center (SSC). Methods used for planning and conducting SSC load tests will be presented, and advanced load-testing techniques will be provided to address runtime issues and enhance verification results. This work was performed at the California Institute of Technology under contract to the National Aeronautics and Space Administration