7,347 research outputs found

    Issues in Evaluating Health Department Web-Based Data Query Systems: Working Papers

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    Compiles papers on conceptual and methodological topics to consider in evaluating state health department systems that provide aggregate data online, such as taxonomy, logic models, indicators, and design. Includes surveys and examples of evaluations

    Can conduction induce convection? The non-linear saturation of buoyancy instabilities in dilute plasmas

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    We study the effects of anisotropic thermal conduction on low-collisionality, astrophysical plasmas using two and three-dimensional magnetohydrodynamic simulations. For weak magnetic fields, dilute plasmas are buoyantly unstable for either sign of the temperature gradient: the heat-flux-driven buoyancy instability (HBI) operates when the temperature increases with radius while the magnetothermal instability (MTI) operates in the opposite limit. In contrast to previous results, we show that, in the presence of a sustained temperature gradient, the MTI drives strong turbulence and operates as an efficient magnetic dynamo (akin to standard, adiabatic convection). Together, the turbulent and magnetic energies contribute up to ~10% of the pressure support in the plasma. In addition, the MTI drives a large convective heat flux, ~1.5% of rho c_s^3. These findings are robust even in the presence of an external source of strong turbulence. Our results on the nonlinear saturation of the HBI are consistent with previous studies but we explain physically why the HBI saturates quiescently by re-orienting the magnetic field (suppressing the conductive heat flux through the plasma), while the MTI saturates by generating sustained turbulence. We also systematically study how an external source of turbulence affects the saturation of the HBI: such turbulence can disrupt the HBI only on scales where the shearing rate of the turbulence is faster than the growth rate of the HBI. In particular, our results provide a simple mapping between the level of turbulence in a plasma and the effective isotropic thermal conductivity. We discuss the astrophysical implications of these findings, with a particular focus on the intracluster medium of galaxy clusters.Comment: 18 pages, 14 figures. Submitted to MNRA

    Motion software for a synergistic six-degree-of-freedom motion base

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    Computer software for the conversion of fixed-base simulations into moving-base simulations utilizing a synergistic six-degree-of-freedom motion simulator has been developed. This software includes an actuator extension transformation, inverse actuator extension transformation, a centroid transformation, and a washout circuit. Particular emphasis is placed upon the washout circuitry as adapted to fit the synergistic motion simulator. The description of the washout circuitry and illustration by means of a sample flight emphasize that translational cue representation may be of good fidelity, but care in the selection of parameters is very necessary, particularly in regard to anomalous rotational cues

    Comparison of a linear and a nonlinear washout for motion simulators utilizing objective and subjective data from CTOL transport landing approaches

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    Objective and subjective data gathered in the processes of comparing a linear and a nonlinear washout for motion simulators reveal that there is no difference in the pilot performance measurements used during instrument landing system (ILS) approaches with a Boeing 737 conventional takeoff and landing (CTOL) airplane between fixed base, linear washout, and nonlinear washout operations. However, the subjective opinions of the pilots reveal an important advance in motion cue presentation. The advance is not in the increased cue available over a linear filter for the same amount of motion base travel but rather in the elimination of false rotational rate cues presented by linear filters

    Empirical comparison of a fixed-base and a moving-base simulation of a helicopter engaged in visually conducted slalom runs

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    Combined visual, motion, and aural cues for a helicopter engaged in visually conducted slalom runs at low altitude were studied. The evaluation of the visual and aural cues was subjective, whereas the motion cues were evaluated both subjectively and objectively. Subjective and objective results coincided in the area of control activity. Generally, less control activity is present under motion conditions than under fixed-base conditions, a fact attributed subjectively to the feeling of realistic limitations of a machine (helicopter) given by the addition of motion cues. The objective data also revealed that the slalom runs were conducted at significantly higher altitudes under motion conditions than under fixed-base conditions

    Evaluation of a linear washout for simulator motion cue presentation during landing approach

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    The comparison of a fixed-base versus a five-degree-of-freedom motion base simulation of a 737 conventional take-off and landing (CTOL) aircraft performing instrument landing system (ILS) landing approaches was used to evaluate a linear motion washout technique. The fact that the pilots felt that the addition of motion increased the pilot workload and this increase was not reflected in the objective data results, indicates that motion cues, as presented, are not a contributing factor to root-mean-square (rms) performance during the landing approach task. Subjective results from standard maneuvering about straight-and-level flight for specific motion cue evaluation revealed that the longitudinal channels (pitch and surge) possibly the yaw channel produce acceptable motions. The roll cue representation, involving both roll and sway channels, was found to be inadequate for large roll inputs, as used for example, in turn entries

    What’s the Story Here? How Catholic University Leaders are Making Sense of Undocumented Student Access.

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    This study examines how leaders make sense of an unsettled, contemporary issue facing higher education. It deepens our understanding of how stories may operate in the process of sensemaking, which has been described as “the experience of being thrown into an ongoing, unknowable, unpredictable streaming of experience in search of answers to the question, ‘What's the story?’” (Weick, 2008, para. 1). Sensemaking is a powerful tool for understanding how people engage volatile issues. The study addresses two research questions: How are Catholic university leaders making sense of undocumented student access? and What role do stories play in the sensemaking of these leaders? Situating the study in Catholic higher education, with its own unique history— serving as a vehicle for assimilation into American society, especially for immigrants—allows us to explore the spiritual and religious values that operate differently within this sector than elsewhere in U.S. higher education. That the issue remains unsettled in policy and practice highlights the effects of volatility on sensemaking. To learn more about how leaders respond to the challenge of this situation, I conducted 55 interviews in 12 Catholic universities in regions of the U.S. with relatively high undocumented populations. I find that identity, social context, extracted cues, and stories play especially important roles in leader sensemaking. Leaders engaged in “constructing Catholic identity,” a process of reflection upon the espoused mission values in their institutions which led to the decision to admit undocumented students. Because of the volatility of undocumented access and leaders’ fear of negative consequences resulting from engaging the issue, leaders employed numerous behaviors to manage their commitment (Salancik, 1977). This resulted in strategic ambiguity that provided some protection for leaders; it also led to communication breakdowns in universities and the alienation of important institutional leaders. Canonical stories played an important role in sensemaking, as leaders referred to “community narratives” and “dominant cultural narratives” (Rappaport, 2000), often alluding to them in shorthand. Because their meaning is shared among group members, canonical stories were especially useful as leaders reflected on the link between institutional histories and charisms and the decision to admit undocumented students.PhDHigher EducationUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/111516/1/djpcsc_1.pd
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