1,318,246 research outputs found
A comparison of Thellier-type and multispecimen paleointensity determinations on Pleistocene and historical lava flows from Lanzarote (Canary Islands, Spain)
Sixteen Miocene, Pleistocene, and historic lava flows have been sampled in Lanzarote (Canary
Islands) for paleointensity analysis with both the Coe and multispecimen methods. Besides obtaining new
data, the main goal of the study was the comparison of paleointensity results determined with two different
techniques. Characteristic Remanent Magnetization (ChRM) directions were obtained in 15 flows, and
12 were chosen for paleointensity determination. In Thellier-type experiments, a selection of reliable
paleointensity determinations (43 of 78 studied samples) was performed using sets of criteria of different
stringency, trying to relate the quality of results to the strictness of the chosen criteria. Uncorrected and
fraction and domain-state corrected multispecimen paleointensity results were obtained in all flows. Results
with the Coe method on historical flows either agree with the expected values or show moderately lower
ones, but multispecimen determinations display a large deviation from the expected result in one case. No
relation can be detected between correct or anomalous results and paleointensity determination quality or
rock-magnetic properties. However, results on historical flows suggest that agreement between both
methods could be a good indicator of correct determinations. Comparison of results obtained with both
methods on seven Pleistocene flows yields an excellent agreement in four and disagreements in three
cases. Pleistocene determinations were only accepted if either results from both methods agreed or a result
was based on a sufficiently large number (n>4) of individual Thellier-type determinations. In most
Pleistocene flows, a VADM around 5 31022 Am2 was observed, although two flows displayed higher values
around 931022 Am2.project
CGL2012-32149 (Ministerio de
Econom ıa y Competitividad, Spain),
project 320/2011 (Ministerio de Medio
Ambiente y Medio Rural y Marino,
Spain) and the European Regional
Development Fund (ERDF)
Models for the Effects of G-seat Cuing on Roll-axis Tracking Performance
Including whole-body motion in a flight simulator improves performance for a variety of tasks requiring a pilot to compensate for the effects of unexpected disturbances. A possible mechanism for this improvement is that whole-body motion provides high derivative vehicle state information whic allows the pilot to generate more lead in responding to the external disturbances. During development of motion simulating algorithms for an advanced g-cuing system it was discovered that an algorithm based on aircraft roll acceleration producted little or no performance improvement. On the other hand, algorithms based on roll position or roll velocity produced performance equivalent to whole-body motion. The analysis and modeling conducted at both the sensory system and manual control performance levels to explain the above results are described
Evolutionary design of a full-envelope full-authority flight control system for an unstable high-performance aircraft
The use of an evolutionary algorithm in the framework of H1 control theory is being considered as a means for synthesizing controller gains that minimize a weighted combination of the infinite norm of the sensitivity function (for disturbance attenuation requirements) and complementary sensitivity function (for robust stability requirements) at the same time. The case study deals with a complete full-authority longitudinal control system for an unstable high-performance jet aircraft featuring (i) a stability and control augmentation system and (ii) autopilot functions (speed and altitude hold). Constraints on closed-loop response are enforced, that representing typical requirements on airplane handling qualities, that makes the control law synthesis process more demanding. Gain scheduling is required, in order to obtain satisfactory performance over the whole flight envelope, so that the synthesis is performed at different reference trim conditions, for several values of the dynamic pressure, used as the scheduling parameter. Nonetheless, the dynamic behaviour of the aircraft may exhibit significant variations when flying at different altitudes, even for the same value of the dynamic pressure, so that a trade-off is required between different feasible controllers synthesized at different altitudes for a given equivalent airspeed. A multiobjective search is thus considered for the determination of the best suited solution to be introduced in the scheduling of the control law. The obtained results are then tested on a longitudinal non-linear model of the aircraft
The effects of bed rest on crew performance during simulated shuttle reentry. Volume 1: Study overview and physiological results
A centrifuge study was carried out to measure physiological stress and control task performance during simulated space shuttle orbiter reentry. Jet pilots were tested with, and without, anti-g-suit protection. The pilots were exposed to simulated space shuttle reentry acceleration profiles before, and after, ten days of complete bed rest, which produced physiological deconditioning similar to that resulting from prolonged exposure to orbital zero g. Pilot performance in selected control tasks was determined during simulated reentry, and before and after each simulation. Physiological stress during reentry was determined by monitoring heart rate, blood pressure, and respiration rate. Study results indicate: (1) heart rate increased during the simulated reentry when no g protection was given, and remained at or below pre-bed rest values when g-suits were used; (2) pilots preferred the use of g-suits to muscular contraction for control of vision tunneling and grayout during reentry; (3) prolonged bed rest did not alter blood pressure or respiration rate during reentry, but the peak reentry acceleration level did; and (4) pilot performance was not affected by prolonged bed rest or simulated reentry
Computer simulation of a single pilot flying a modern high-performance helicopter
Presented is a computer simulation of a human response pilot model able to execute operational flight maneuvers and vehicle stabilization of a modern high-performance helicopter. Low-order, single-variable, human response mechanisms, integrated to form a multivariable pilot structure, provide a comprehensive operational control over the vehicle. Evaluations of the integrated pilot were performed by direct insertion into a nonlinear, total-force simulation environment provided by NASA Lewis. Comparisons between the integrated pilot structure and single-variable pilot mechanisms are presented. Static and dynamically alterable configurations of the pilot structure are introduced to simulate pilot activities during vehicle maneuvers. These configurations, in conjunction with higher level, decision-making processes, are considered for use where guidance and navigational procedures, operational mode transfers, and resource sharing are required
The Philippine Health Institutions: Some Problems, Approaches and Policy Issues
This paper presents a brief analysis of the current situation of Philippine health institutions using secondary data. It locates the different types of health institutions, describes its major problems, discusses recent approaches these institutions have adopted to improve delivery of health care services and extricates policy-related issues and data gaps from available literature.health sector, hospitals, hospital care, health centers
Blending online and offline anxiety treatment in routine mental health care:Research on acceptability, effectiveness and cost-effectiveness of Internet-supported and blended cognitive behavioral therapy for patients with severe anxiety disorders
G-load indicator and warning device for aircraft
Device facilitates pilot control of g-load maneuvers and provides immediate indication of g-load constraint violations. It may be used in test flights, in aircraft simulators, or in displays of performance of remotely piloted aircraft
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