Changes in Pilot Control Behaviour across Stewart Platform Motion Systems

Low-cost motion systems have been proposed for certain training tasks that would otherwise be performed on high-performance full flight simulators. These systems have shorter stroke actuators, lower bandwidth, and higher noise. The influence of these characteristics on pilot perception and control behaviour is unknown, and can be investigated by simulating a model of a simulator with limited capabilities on a high-end simulator. The platform limitations, such as a platform filter, time delay, and simulator noise characteristics, can then be removed one by one and their effect on control behaviour studied in isolation. By applying a cybernetic approach, human behaviour can be measured objectively in target-following disturbance-rejection control tasks. Experimental results show that small changes in time delay and simulator noise characteristics do not negatively affect human behaviour in these tasks. However, the motion system bandwidth has a significant effect on performance and control behaviour. Participants barely use motion cues when these have a low bandwidth, and instead rely on visual cues to generate lead to perform the control task. Therefore, simulator motion cues must be considered carefully in piloted control tasks in simulators and measured results depend on simulator characteristics as pilots adapt their control behaviour to the available cues

On the size and shape of excluded volume polymers confined between parallel plates

A number of recent experiments have provided detailed observations of the configurations of long DNA strands under nano-to-micrometer sized confinement. We therefore revisit the problem of an excluded volume polymer chain confined between two parallel plates with varying plate separation. We show that the non-monotonic behavior of the overall size of the chain as a function of plate-separation, seen in computer simulations and reproduced by earlier theories, can already be predicted on the basis of scaling arguments. However, the behavior of the size in a plane parallel to the plates, a quantity observed in recent experiments, is predicted to be monotonic, in contrast to the experimental findings. We analyze this problem in depth with a mean-field approach that maps the confined polymer onto an anisotropic Gaussian chain, which allows the size of the polymer to be determined separately in the confined and unconfined directions. The theory allows the analytical construction of a smooth cross-over between the small plate-separation de Gennes regime and the large plate-separation Flory regime. The results show good agreement with Langevin dynamics simulations, and confirm the scaling predictions.Comment: 15 pages, 3 figure

Sleutel van het verleden, sleutel tot de toekomst : de roemrijke cultuurhistorie van de Rijnstrangen als drijvende kracht voor economische vernieuwing. Een evaluatie van kwaliteiten en kansen

In het Rijnstrangengebied is het van groot belang om aan te sluiten bij ontwikkelingen, want er is sprake van een grote ruimtelijke dynamiek. Er zijn opgaven voor natuur, water en de landbouw. Daarnaast kent het gebied een grote toeristische en recreatieve potentie. Bij deze opgaven kan cultuurhistorie een rode lijn zijn, een verbindende factor

Design of an Ecological Vertical Separation Assistance Cockpit Display

A tactical navigation support tool was designed to effectively deal with conflict situations in the vertical plane, while preserving travel freedom as much as possible. Based on Ecological Interface Design principles, the Vertical Separation Assistance Display is developed as an extension to the existing Vertical Situation Display. Functional information is presented via overlays that show pilots how their vertical maneuvering possibilities are constrained by ownship performance, and by limits imposed by surrounding traffic. A questionnaire-based evaluation shows that the ecological overlays considerably improved pilot traffic awareness in vertical conflict situations

Axiomatic Characterization of the Mean Function on Trees

A mean of a sequence π = (x1, x2, . . . , xk) of elements of a finite metric space (X, d) is an element x for which is minimum. The function Mean whose domain is the set of all finite sequences on X and is defined by Mean(π) = { x | x is a mean of π } is called the mean function on X. In this paper the mean function on finite trees is characterized axiomatically

Investigation of the Effects of Autorotative Flare Index Variation on Helicopter Flight Dynamics in Autorotation

Autorotation is a flight condition whereby the engine of a helicopter is no longer supplying power to the main rotor system, which is driven solely by the upward flow of the air moving through the rotor. For helicopters, autorotation is a common emergency procedure performed by pilots to safely land the vehicle in the event of a power failure or tail-rotor failure. In the classic analysis of dynamic stability of helicopters in powered flight, it is common practice to neglect the effect of variation of rotor angular velocity, as the rotorspeed is constant. However, this assumption is no longer justified in case of autorotative flight. Therefore, the rotorspeed becomes an additional degree-of-freedom in autorotation, giving rise to a new stability mode that couples with classical rigid-body modes. The present paper aims at understanding the role of the rotorspeed degree-of-freedom in modifying the stability characteristics in autorotation of rotor systems with different autorotative flare indexes. Results show that the helicopter dynamics are considerably affected in autorotation as a consequence of the fact that the rotorspeed degree of freedom couples with the heave subsidence mode. Therefore, autorotation requires a different control strategy by the pilot and should not be mistakenly considered only as an energy management task. Furthermore, the autorotative flare index, used to characterize the autorotative performance during the preliminary design phase of a new helicopter, provides only energy information. Indeed, this paper demonstrates that high values of this index, representative of good autorotative performance in terms of available energy over required energy, may lead to degraded stability characteristics of the helicopter in autorotation.Control & Simulatio

Ultraviolet Signposts of Resonant Dynamics in the Starburst-Ringed Sab Galaxy, M94 (NGC 4736)

M94 (NGC 4736) is investigated using images from the Ultraviolet Imaging Telescope (FUV-band), Hubble Space Telescope (NUV-band), Kitt Peak 0.9-m telescope (H-alpha, R, and I bands), and Palomar 5-m telescope (B-band), along with spectra from the International Ultraviolet Explorer and Lick 1-m telescopes. The wide-field UIT image shows FUV emission from (a) an elongated nucleus, (b) a diffuse inner disk, where H-alpha is observed in absorption, (c) a bright inner ring of H II regions at the perimeter of the inner disk (R = 48 arcsec. = 1.1 kpc), and (d) two 500-pc size knots of hot stars exterior to the ring on diametrically opposite sides of the nucleus (R= 130 arcsec. = 2.9 kpc). The HST/FOC image resolves the NUV emission from the nuclear region into a bright core and a faint 20 arcsec. long ``mini-bar'' at a position angle of 30 deg. Optical and IUE spectroscopy of the nucleus and diffuse inner disk indicates an approximately 10^7 or 10^8 yr-old stellar population from low-level starbirth activity blended with some LINER activity. Analysis of the H-alpha, FUV, NUV, B, R, and I-band emission along with other observed tracers of stars and gas in M94 indicates that most of the star formation is being orchestrated via ring-bar dynamics involving the nuclear mini-bar, inner ring, oval disk, and outer ring. The inner starburst ring and bi-symmetric knots at intermediate radius, in particular, argue for bar-mediated resonances as the primary drivers of evolution in M94 at the present epoch. Similar processes may be governing the evolution of the ``core-dominated'' galaxies that have been observed at high redshift. The gravitationally-lensed ``Pretzel Galaxy'' (0024+1654) at a redshift of approximately 1.5 provides an important precedent in this regard.Comment: revised figure 1 (corrected coordinate labels on declination axis); 19 pages of text + 19 figures (jpg files); accepted for publication in A

Extramural Venous Invasion as Prognostic Factor of Recurrence in Stage 1 and 2 Colon Cancer

Aim. Extramural venous invasion (EMVI) is a prognostic indicator in patients with colorectal cancer. However, its additional value in patients with stage 1 and 2 colorectal cancer is uncertain. In the present study, the incidence of EMVI and the hazard ratio for recurrence in patients with stage 1 and 2 colon cancer were studied. Methods. 184 patients treated for stage 1 and 2 colon cancer were included with a follow-up of at least 5 years. Chart review was performed and EMVI was assessed by two separate pathologists. EMVI was scored with additional caldesmon staining on the resection specimen. Primary outcomes were recurrence-free survival (RFS) measured through the Cox regression analysis and prevalence of EMVI. Results. There were 10 cases of EMVI and 3 cases of intramural venous invasion (IMVI) all occurring in patients with stage 2 disease corresponding to a prevalence of 9%. Thirty-one percent of the patients with venous invasion experienced recurrence versus 14% in patients without, corresponding with a hazard ratio of 2.39 (p=0.11). Conclusion. The present study demonstrates a trend towards an increased risk of recurrence in patients with stage 2 colon cancer with venous invasion. This warrants consideration of adjuvant chemotherapy despite the lack of lymph node metastases

Faculty and student perceptions of the feasibility of individual student–faculty meetings

The extent to which students feel involved in their education positively influences academic achievement. Individual student–faculty meetings can foster student involvement. To be effective, faculty acknowledgement of the benefit of these meetings is a prerequisite. The aim of this study was to explore faculty perceptions of individual student–faculty meetings. In addition we investigated students’ perceptions. As part of the undergraduate programme, mandatory individual intake and follow-up meetings between first-year medical students (n = 425) and senior faculty members (n = 34) have been implemented from 2009 onwards. We administered a questionnaire on faculty perceptions of the benefit and impact of intake meetings. Subsequently, after both meetings had been held, strong and weak points of the mandatory programme were explored using open-ended questions. Students’ perceptions were investigated by open-ended questions as a part of the curriculum evaluation process. Faculty enjoyed the meetings (90 %), perceived the meetings to be beneficial (74 %) and expected a positive effect on student involvement (74 %). Faculty appreciated the opportunity to give advice tailored to students’ personal needs and levels of performance. The students appreciated the meetings and the attention given to their personal situation and study progress. Faculty and student appreciation of the meetings seems to support the assumption that the individual meetings increase students’ social and academic involvement. Further research should focus on the impact of individual student–faculty meetings on students’ learning behaviours

Symbiotic Ocean Modeling Using Physics-Controlled Echo State Networks

We introduce a “symbiotic” ocean modeling strategy that leverages data-driven and machine learning methods to allow high- and low-resolution dynamical models to mutually benefit from each other. In this work we mainly focus on how a low-resolution model can be enhanced within a symbiotic model configuration. The broader aim is to enhance the representation of unresolved processes in low-resolution models, while simultaneously improving the efficiency of high-resolution models. To achieve this, we use a grid-switching approach together with hybrid modeling techniques that combine linear regression-based methods with nonlinear echo state networks. The approach is applied to both the Kuramoto–Sivashinsky equation and a single-layer quasi-geostrophic ocean model, and shown to simulate short-term and long-term behavior better than either purely data-based methods or low-resolution models. By maintaining key flow characteristics, the hybrid modeling techniques are also able to provide higher quality initial conditions for high-resolution models, thereby improving their efficiency.</p