2,786 research outputs found

    Frequency‐Dependent Moment Tensors of Induced Microearthquakes

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    Analysis of 984 induced microearthquakes from The Geysers geothermal reservoir in California reveals that the retrieved moment tensors depend on the frequency band of the inverted waveforms. The observed dependence is more significant for the percentages of the double‐couple, compensated linear vector dipole, and isotropic (ISO) components than for the focal mechanisms. The average root‐mean‐square of the moment tensors obtained in different frequency bands is correlated with spectra of ambient noise. The percentages of double‐couple and ISO components tend to decrease and increase with the upper cutoff frequency (fu), respectively. This suggests that shear rupture radiates energy preferentially in a lower frequency band and tensile rupture in a higher frequency band. Events displaying a strong increase of the ISO with fu are confined within the same depth interval as the injection points. This might be related to the strong thermoelastic effects in the vicinity of injection points that promote opening of small cracks adjacent to the main fractures

    Neutrinos from Early-Phase, Pulsar-Driven Supernovae

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    Neutron stars, just after their formation, are surrounded by expanding, dense, and very hot envelopes which radiate thermal photons. Iron nuclei can be accelerated in the wind zones of such energetic pulsars to very high energies. These nuclei photo-disintegrate and their products lose energy efficiently in collisions with thermal photons and with the matter of the envelope, mainly via pion production. When the temperature of the radiation inside the envelope of the supernova drops below ∌3×106\sim 3\times 10^6 K, these pions decay before losing energy and produce high energy neutrinos. We estimate the flux of muon neutrinos emitted during such an early phase of the pulsar - supernova envelope interaction. We find that a 1 km2^2 neutrino detector should be able to detect neutrinos above 1 TeV within about one year after the explosion from a supernova in our Galaxy. This result holds if these pulsars are able to efficiently accelerate nuclei to energies ∌1020\sim 10^{20} eV, as postulated recently by some authors for models of Galactic acceleration of the extremely high energy cosmic rays (EHE CRs).Comment: 16 pages, 3 figures, revised version submitted to Ap

    Photo sensor array technology development

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    The development of an improved capability photo sensor array imager for use in a Viking '75 type facsimile camera is presented. This imager consists of silicon photodiodes and lead sulfide detectors to cover a spectral range from 0.4 to 2.7 microns. An optical design specifying filter configurations and convergence angles is described. Three electronics design approaches: AC-chopped light, DC-dual detector, and DC-single detector, are investigated. Experimental and calculated results are compared whenever possible using breadboard testing and tolerance analysis techniques. Results show that any design used must be forgiving of the relative instability of lead sulfide detectors. A final design using lead sulfide detectors and associated electronics is implemented by fabrication of a hybrid prototype device. Test results of this device show a good agreement with calculated values

    Study of SEM induced current and voltage contrast modes to assess semiconductor reliability

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    The purpose of the scanning electron microscopy study was to review the failure history of existing integrated circuit technologies to identify predominant failure mechanisms, and to evaluate the feasibility of their detection using SEM application techniques. The study investigated the effects of E-beam irradiation damage and contamination deposition rates; developed the necessary methods for applying the techniques to the detection of latent defects and weaknesses in integrated circuits; and made recommendations for applying the techniques

    Neuropsychological and information processing deficits following mild traumatic brain injury

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    Neuroradiological and neuropathological investigations have found evidence of diffuse brain damage in the frontal and temporal lobes, corpus callosum, and fornices in patients who have sustained a mild traumatic brain injury (TBI). However, neuropsychological assessments of these patients do not typically target many of the subtle information processing deficits that may arise from diffuse damage involving the frontotemporal regions of the brain as well as white matter pathology, including the corpus callosum. Consequently, we have a limited understanding of the deficits that may be attributable to temporary or permanent disruptions to these functional pathways. This study assessed a group of mild TBI patients (N = 40) and a matched control group (N = 40) on a number of standard neuropsychological tests of selective and sustained attention, verbal and non-verbal fluency, and verbal memory. In addition, reaction time (RT) tasks, requiring both the inter- and intra-hemispheric processing of visual and tactile information, were used to assess the functional integrity of the tracts that are likely to be affected by diffuse damage. In the 1st month after sustaining their injury, the mild TBI group demonstrated deficits in attention, non-verbal fluency, and verbal memory. They also demonstrated slower visual and tactile RTs, with the visual RTs of mild TBI patients being more affected by increased task difficulty and the need to transfer information across the corpus callosum, than did their matched controls.Jane L. Mathias, Jaqcui A. Beall and Erin D. Bigle

    On the Physical Environment in the Galactic Nuclei

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    Galactic nuclei and quasars emit radiation over the entire electromagnetic spectrum. This suggests that concurrent observations over a wide frequency range may provide useful information in determining appropriate models for the physical environment in which the radiation is produced. In conjunction with observations by the high energy spectrometer on OSO-8, four sources have been studied in this manner; the nucleus of the elliptical galaxy, Centaurus A (NGG 5128); the quasar, 30273; the Seyfert galaxy, NGC 4151 and the nucleus of the Milky Way (GCX). Concurrent observations are used to construct the composite spectra (from radio to X-ray) for Cen A and NGC 4151 while the composite spectra of 30273 and GCX are derived from the OSO-8 data and from other observers. A skymap technique used to analyze observations of the galactic center region yielded data consistent with a significant, hard X-ray source at the radio and infrared position of the nucleus of the Milky Way. A theoretical analysis of the temporal variability of the Cen A data is undertaken and its implications discussed. Similarities between the composite spectra of the observed sources suggest that radio-bright and radio-quiet quasars may represent the emission from galactic nuclei with elliptical and Seyfert-like morphologies, respectively

    PRELIMINARY RESULTS OF THE SNAP 2 EXPERIMENTAL REACTOR

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    The operating history of the SNAP 2 Experimental Reactor (SER) and the preliminary results from the testing program are presented. The total energy generated during the life of the reactor was 224,650 kilowatt hours. This is equivalent to approximately one-half year of full-power operation. The methods used to obtain the reactor parameters are also described. The experimental data obtained were generally in excellent agreement with calculated valuess The principal comparisons are tabulated. (auth

    Exploring the Referral and Usage of Science Fiction in HCI Literature

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    Research on science fiction (sci-fi) in scientific publications has indicated the usage of sci-fi stories, movies or shows to inspire novel Human-Computer Interaction (HCI) research. Yet no studies have analysed sci-fi in a top-ranked computer science conference at present. For that reason, we examine the CHI main track for the presence and nature of sci-fi referrals in relationship to HCI research. We search for six sci-fi terms in a dataset of 5812 CHI main proceedings and code the context of 175 sci-fi referrals in 83 papers indexed in the CHI main track. In our results, we categorize these papers into five contemporary HCI research themes wherein sci-fi and HCI interconnect: 1) Theoretical Design Research; 2) New Interactions; 3) Human-Body Modification or Extension; 4) Human-Robot Interaction and Artificial Intelligence; and 5) Visions of Computing and HCI. In conclusion, we discuss results and implications located in the promising arena of sci-fi and HCI research.Comment: v1: 20 pages, 4 figures, 3 tables, HCI International 2018 accepted submission v2: 20 pages, 4 figures, 3 tables, added link/doi for Springer proceedin
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