Driver detection and recognition of lineside signals and signs at different approach speeds

A study was carried out using simulation to investigate driver responses to lineside signals and signs at various approach speeds. The objectives of the study were: (1) to find out whether train speed would significantly affect signal/sign reading; (2) to examine at which point certain types of signs or signals could be detected or recognised, and (3) to determine a speed cut-off level above which certain types of signs or signals are no longer recognisable or detectable. Fifty-seven train drivers from 12 Train Operating Companies in the UK participated in the trials. Twenty different types of lineside signs and ten types of signals were tested under six different approach speeds ranging from 100 to 350 km/h (62–218 mph). Driver performance measures were ‘time remaining to the signal/sign’ at the point of detection or recognition, and reading error rate. The results showed a significant influence of train speed on driver responses to lineside signals/signs and demonstrated a non-linear relationship between driver responses to signals/signs and approach speed. This has been used to estimate a maximum approach speed limit within which a specific signal or sign can be correctly detected or recognised. The findings and implications of the study are discussed in the paper.     

Halo effects in grading student projects.

Halo effects in rating specific pieces of work, as in educational grading, have received little attention. Grades awarded by 2 independent graders to undergraduate projects were analyzed with a correlated uniqueness model. Grades showed substantial halo despite being awarded by expert assessors at the time of reading the work. There was greater halo between different grades applying to the same section of the project than between grades applying to different sections. Supervisors who had regular contact with the student whose work they were grading showed no more halo than other graders. More reliable graders showed less within-section halo than graders of lower reliability but equal between-sections halo. The halo effects observed cannot be entirely attributable to a unitary general impression. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Anatomical suitability of abdominal aortic aneurysms for endovascular repair

BACKGROUND: Aortic aneurysm anatomy is crucial when considering patients for endovascular repair. The aim of this study was to determine the proportion of patients with aortic aneurysm suitable for endovascular repair with three different graft-stent systems. METHODS: Spiral computed tomographic angiography was used to assess the anatomy of 154 abdominal aortic aneurysms. Measurements were made of aneurysm neck length and diameter, renal artery to aortic bifurcation length, common iliac artery diameter and length, and external iliac artery diameter. Aneurysms were assessed for anatomical suitability for currently available aortoaortic, aortobi-iliac and aortouni-iliac devices. RESULTS: Six patients (4 per cent) had a distal aortic neck suitable for implantation of a straight aortic graft. Fifteen patients (10 per cent) had arterial anatomy suitable for implantation of a bifurcated graft and 85 (55 per cent) patients were suitable for endovascular repair with an aortouni-iliac graft. The primary reasons for unsuitability were: proximal neck length less than 1.5 cm (44 patients), proximal neck diameter greater than 3.0 cm (12), and angulation of the proximal neck (three). A further ten patients were considered unsuitable for an aortouni-iliac graft because of bilateral common iliac artery aneurysms (four), tortuous iliac arteries (four) and narrow external iliac arteries (two). CONCLUSION: The aortouni-iliac device has the widest applicability of the currently available endovascular systems but open repair remains the only option for a large proportion of patients.     

The generation effect is no artifact: Generating makes words distinctive.

The generation effect occurs if people remember items they complete from fragments better than complete items they read. Four experiments investigate two questions. When does the effect occur, and why does it do so? Targets generated in related contexts are recognized better than read targets, and they are recalled better with the contexts as cues; the contexts are recognized equally well, and the relation between the context and target is not enhanced by generation. Furthermore, generated items exceed items read in pure lists even when read ones from the mixed list are no worse than the controls. The generation effect is real; it is not an artifact. However, there is nothing special about generation. Generating is a type of encoding, and like any other type of encoding, its effects are maximal on tests that require subjects to do again whatever they did at study. Generating makes targets distinctive by contrasting them with other relatives of the context, and, as a result, the targets enjoy benefits in later discriminations within their family. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Periodic dynamics of coupled cell networks I: rigid patterns of synchrony and phase relations

It has recently been proved by Golubitsky and coworkers that in any network of coupled dynamical systems, the possible 'rigid' patterns of synchrony of hyperbolic equilibria are determined by purely combinatorial properties of the network, known as 'balanced equivalence relations'. A pattern is 'rigid' if it persists under small 'admissible' perturbations of the differential equation — ones that respect the network structure. We discuss a natural generalisation of these ideas to time-periodic states, and motivate two basic conjectures, the Rigid Synchrony Conjecture and the Rigid Phase Conjecture. These conjectures state that for rigid hyperbolic time-periodic patterns, cells with synchronous dynamics must have synchronous input cells, and cells with phase-related dynamics must have input cells that have the same phase relations. We provide evidence supporting the two conjectures, by proving them for a special class of periodic orbits, which we call 'tame', under strong assumptions on the network architecture and the symmetries of the periodic state. The discussion takes place in the formal setting of coupled cell networks. We prove that rigid patterns of synchrony are balanced, together with the analogous result for rigid patterns of phase relations. The assumption on the network architecture simplifies the geometry of admissible vector fields, while tameness rules out patterns with non-trivial local or multilocal symmetry. The main idea is to perturb an admissible vector field in a way that retains sufficient control over the associated perturbed periodic orbit. We present two techniques for constructing these perturbations, both using a general theorem on groupoid-symmetrisation of vector fields, which has independent interest. In particular we introduce a method of 'patching' that makes local changes to an admissible vector field. Having established these results for all-to-all coupled networks and tame periodic orbits we prove more general versions that require these assumptions only on a suitable quotient network. These conditions are weaker and encompass a larger class of networks and periodic orbits. We give an example to show that rigidity cannot be relaxed to hyperbolicity. We also prove, without any technical assumptions, that rigidly synchronous or phase-related cells must be input-isomorphic, a necessary precondition for the two conjectures to hold.