4,147 research outputs found

    Documenting Current Instructional Design Practices: Towards a Typology of Instructional Designer Activities, Roles, and Collaboration

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    The overall goal of this study was to conduct a yearlong inquiry into an instructional designer’s activities and interactions with his clients. Exclusive focus of this study was on an instructional designer who worked at a large public university in the southeastern region of the United States. Documented in an instructional design activities log, this study analyzed 115 distinct activities. Using an emergent theme analysis approach, specific instructional design activities and roles emerged. In addition, the instructional designer’s collaboration with his clients was analyzed. Results of this study augment the knowledge base of existing studies of instructional design practices

    Lafitau et la pensée ethnologique de son temps

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    The Case for State Pollution Taxes

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    Visual suppression of the vestibulo-ocular reflex during space flight

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    Visual suppression of the vestibulo-ocular reflex was studied in 16 subjects on 4 Space Shuttle missions. Eye movements were recorded by electro-oculography while subjects fixated a head mounted target during active sinusoidal head oscillation at 0.3 Hz. Adequacy of suppression was evaluated by the number of nystagmus beats, the mean amplitude of each beat, and the cumulative amplitude of nystagmus during two head oscillation cycles. Vestibulo-ocular reflex suppression was unaffected by space flight. Subjects with space motion sickness during flight had significantly more nystagmus beats than unaffected individuals. These susceptible subjects also tended to have more nystagmus beats before flight

    Eye and head motion during head turns in spaceflight

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    Eye-head motion was studied pre-, in- and postflight during single voluntary head turns. A transient increase in vestibulo-ocular reflex (VOR) gain occurred early in the flight, but later trended toward normal. This increased gain was produced by a relative increase in eye counterrotation velocity. Asymmetries in gain with right and left turns also occurred, caused by asymmetries in eye counterrotation velocities. These findings were remarkably similar to those from Soviet primate studies using gaze fixation targets, except the human study trended more rapidly toward normal. These findings differ substantially from those measuring VOR gain by head oscillation, in which no significant changes were found inflight. No visual disturbances were noted in either test condition or in normal activities. These head turn studies are the only ones to date documenting any functional change in VOR in weightlessness

    Studies of the vestibulo-ocular reflex on STS 4, 5 and 6

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    The vestibulo-ocular reflex (VOR) may be altered by weightlessness. Since this reflex plays a large role in visual stabilization, it was important to document any changes caused by space flight. This is a report on findings on STS-4 through 6 and is part of a larger study of neurosensory adaptation done on STS-4 through 8. Voluntary horizontal head oscillations at 1/3 Hz with amplitude of 30 deg right and left of center were recorded by a potentiometer and compared to eye position recorded by electroculography under the following conditions: eyes open, head fixed, tracking horizontal targets switched 0, 15, and 30 degrees right and left (optokinetic reflex - OKR - and calibration); eyes open and fixed on static external target with oscillation, (vestibulo ocular reflex, eyes closed - VOR EC); eyes open and wearing opaque goggles with target fixed in imagination (vestibulo-ocular reflex, eyes shaded - VOR ES); and eyes open and fixed on a head synchronized target with head oscillation (VOR suppression). No significant changes were found in voluntary head oscillation frequency or amplitude in those with (n=5), and without (n=3), space motion sickness (SMS), with phase of flight or test condition. Variations in head oscillation were too small to have produced detectable changes in test results

    Studies of the horizontal vestibulo-ocular reflex on STS 7 and 8

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    Unpaced voluntary horizontal head oscillation was used to study the Vestibulo-Ocular Reflex (VOR) on Shuttle flights STS 7 and 8. Ten subjects performed head oscillations at 0.33 Hz + or - 30 deg amplitude under the followng conditions: VVOR (visual VOR), eyes open and fixed on a stationary target; VOR-EC, with eyes closed and fixed on the same target in imagination; and VOR-S (VOR suppression), with eyes open and fixed on a head-synchronized target. Effects of weightlessness, flight phase, and Space Motion Sickness (SMS) on head oscillation characteristics were examined. A significant increase in head oscillation frequency was noted inflight in subjects free from SMS. In subjects susceptible to SMS, frequency was reduced during their Symptomatic period. The data also suggest that the amplitude and peak velocity of head oscillation were reduced early inflight. No significant changes were noted in reflex gain or phase in any of the test conditions; however, there was a suggestion of an increase in VVOR and VOR-ES gain early inflight in asymptomatic subjects. A significant difference in VOR-S was found between SMS susceptible and non-susceptible subjects. There is no evidence that any changes in VOR characteristics contributed to SMS

    Arctic Marine Terminals -- Some Environmental and Engineering Considerations

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    Studies are presently underway to determine the technical and economic feasibility of various Arctic marine transportation systems, including ice-breaker super-tankers and submarine tankers. An important consideration in these studies is the design and construction of marine terminal facilities which will be suited to the unique problems of the Arctic. Factors which will significantly affect the design of proposed marine terminals include: 1) bathymetric configuration of the continental shelf;2) influence of moving pack ice on artificial structures, both at the air-water interface and along the bottom;3) lateral and vertical variations in soil conditions, including residual permafrost, which might adversely affect stability of offshore pipelines or structures; and4) instability of existing shoreline. Several basic designs for marine terminals are considered with respect to environmental and engineering problems including:1) nearshore harbor sheltered by a breakwater;2) offshore artificial islands;3) underwater terminals; and4) cone-shaped offshore platforms, either pile supported or gravity-type structures

    Saccadic eye movement during spaceflight

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    Saccadic eye movements were studied in six subjects during two Space Shuttle missions. Reaction time, peak velocity and accuracy of horizontal, visually-guided saccades were examined preflight, inflight and postflight. Conventional electro-oculography was used to record eye position, with the subjects responding to pseudo-randomly illuminated targets at 0 deg and + or - 10 deg and 20 deg visual angles. In all subjects, preflight measurements were within normal limits. Reaction time was significantly increased inflight, while peak velocity was significantly decreased. A tendency toward a greater proportion of hypometric saccades inflight was also noted. Possible explanations for these changes and possible correlations with space motion sickness are discussed
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