10,358 research outputs found

    Study of space cabin atmospheres Semiannual status report, 1 Jul. - 31 Dec. 1965

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    Space cabin atmospheres - space cabin aerosol sampling device, field aerosol generator, and survey of particle counter design

    Respiratory protective device design using control system techniques

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    The feasibility of a control system analysis approach to provide a design base for respiratory protective devices is considered. A system design approach requires that all functions and components of the system be mathematically identified in a model of the RPD. The mathematical notations describe the operation of the components as closely as possible. The individual component mathematical descriptions are then combined to describe the complete RPD. Finally, analysis of the mathematical notation by control system theory is used to derive compensating component values that force the system to operate in a stable and predictable manner

    Study of space cabin atmospheres Status report, Jul. 1 - Dec. 31, 1967

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    Calibration of hot-wire detector for particle concentration and size distribution in closed spacecraft cabin atmosphere

    Study of Space Cabin Atmospheres Status Report, 1 Jan. - 30 Jun. 1966

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    Performance characteristics of aerosol generator, and distribution sampling errors of electrostatic precipitator sampling device for space cabin atmospher

    Initial states and infrared physics in locally de Sitter spacetime

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    The long wavelength physics in a de Sitter region depends on the initial quantum state. While such long wavelength physics is under control for massive fields near the Hartle-Hawking vacuum state, such initial states make unnatural assumptions about initial data outside the region of causal contact of a local observer. We argue that a reasonable approximation to a maximum entropy state, one that makes minimal assumptions outside an observer's horizon volume, is one where a cutoff is placed on a surface bounded by timelike geodesics, just outside the horizon. For sufficiently early times, such a cutoff induces secular logarithmic divergences with the expansion of the region. For massive fields, these effects sum to finite corrections at sufficiently late times. The difference between the cutoff correlators and Hartle-Hawking correlators provides a measure of the theoretical uncertainty due to lack of knowledge of the initial state in causally disconnected regions. These differences are negligible for primordial inflation, but can become significant during epochs with very long-lived de Sitter regions, such as we may be entering now.Comment: 19 pages, 4 figures, references adde

    The trauma memory quality questionnaire:Preliminary development and validation of a measure of trauma memory characteristics for children and adolescents

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    It has been suggested that post-traumatic stress is related to the nature of an individual's trauma memories. While this hypothesis has received support in adults, few studies have examined this in children and adolescents. This article describes the development and validation of a measure of the nature of children's trauma memories, the Trauma Memory Quality Questionnaire (TMQQ), that might test this hypothesis and be of clinical use. The measure was standardised in two samples, a cross-sectional sample of non-clinic referred secondary school pupils (n=254), and a sample participating in a prospective study of children and adolescents who had attended a hospital Accident and Emergency department following an assault or a road traffic accident (n=106). The TMQQ was found to possess good internal consistency, criterion validity, and construct validity, but test-retest reliability has yet to be established

    Bouncing Cosmology in Three Dimensions

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    We consider a dynamical two-brane in a four dimensional black hole background with scalar hair. At high temperature this black hole goes through a phase transition by radiating away the scalar. The end phase is a topological adS-Schwarzschild black hole. We argue here that for a sufficiently low temperature, the brane motion in this geometry is non-singular. This results in a universe which passes over from a contracting phase to an expanding one without reaching a singularity.Comment: 7 pages, LaTex, 3 figures, Journal versio

    Study of space cabin atmospheres Semiannual progress report, 1 Jan. - 30 Jun. 1968

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    Aerosol measurements in closed cabin environment optimizing geometry of aerosol particle analyzer, and calibrating hot-wire droplet senso

    The S2 VLBI Correlator: A Correlator for Space VLBI and Geodetic Signal Processing

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    We describe the design of a correlator system for ground and space-based VLBI. The correlator contains unique signal processing functions: flexible LO frequency switching for bandwidth synthesis; 1 ms dump intervals, multi-rate digital signal-processing techniques to allow correlation of signals at different sample rates; and a digital filter for very high resolution cross-power spectra. It also includes autocorrelation, tone extraction, pulsar gating, signal-statistics accumulation.Comment: 44 pages, 13 figure
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