Human Factors Standards and the Hard Human Factor Problems: Observations on Medical Usability Standards

With increasing variety and sophistication of computer-based medical devices, and more diverse users and use environments, usability is essential, especially to ensure safety. Usability standards and guidelines play an important role. We reviewed several, focusing on the IEC 62366 and 60601 sets. It is plausible that these standards have reduced risks for patients, but we raise concerns regarding: (1) complex design trade-offs that are not addressed, (2) a focus on user interface design (e.g., making alarms audible) to the detriment of other human factors (e.g., ensuring users actually act upon alarms they hear), and (3) some definitions and scope restrictions that may create “blind spots”. We highlight potential related risks, e.g. that clear directives on “easier to understand” risks, though useful, may preclude mitigating other, more “difficult” ones; but ask to what extent these negative effects can be avoided by standard writers, given objective constraints. Our critique is motivated by current research and incident reports, and considers standards from other domains and countries. It is meant to highlight problems, relevant to designers, standards committees, and human factors researchers, and to trigger discussion about the potential and limits of standards

Influence of Mortar Rheology on Aggregate Settlement

The influence of the rheology of fresh concrete on the settlement of aggregate is examined. Fresh concrete exhibits a yield stress that, under certain conditions, prevents the settlement of coarse aggregate, although its density is larger than that of the suspending mortar. Calculations, based on estimates of the yield stress obtained from slump tests, predict that aggregate normally used in concrete should not sink. To test this prediction, the settlement of a stone in fresh mortar is monitored. The stone does not sink in the undisturbed mortar (which has a high yield stress), but sinks when the mortar is vibrated, presumably due to a large reduction in its yield stress. This implies that during placement of concrete, the aggregate settles only while the concrete is being vibrated. A unique experimental method for measuring aggregate settlement is also introduced and demonstrated

Thixotropy in macroscopic suspensions of spheres

An experimental study of the viscosity of a macroscopic suspension, i.e. a suspension for which Brownian motion can be neglected, under steady shear is presented. The suspension is prepared with a high packing fraction and is density-matched in a Newtonian carrier fluid. The viscosity of the suspension depends on the shear rate and the time of shearing. It is shown for the first time that a macroscopic suspension shows thixotropic viscosity, i.e. shear-thinning with a long relaxation time as a unique function of shear. The relaxation times show a systematic decrease with increasing shear rate. These relaxation times are larger when decreasing the shear rates, compared to those observed after increasing the shear. The time scales involved are about 10000 times larger than the viscous time scale and about 1000 times smaller than the thermodynamic time scale. The structure of the suspension at the outer cylinder of a viscometer is monitored with a camera, showing the formation of a hexagonal structure. The temporal decrease of the viscosity under shear coincides with the formation of this hexagonal pattern

Quasi ALE finite element method for nonlinear water waves

This paper presents a newly developed quasi arbitrary Lagrangian-Eulerian finite element method (QALE-FEM) for simulating water waves based on fully nonlinear potential theory. The main difference of this method from the conventional finite element method developed by one of authors of this paper and others (see, e.g., [11] and [22]) is that the complex mesh is generated only once at the beginning and is moved at all other time steps in order to conform to the motion of the free surface and structures. This feature allows one to use an unstructured mesh with any degree of complexity without the need of regenerating it every time step, which is generally inevitable and very costly. Due to this feature, the QALE-FEM has high potential in enhancing computational efficiency when applied to problems associated with the complex interaction between large steep waves and structures since the use of an unstructured mesh in such a case is likely to be necessary. To achieve overall high efficiency, the numerical techniques involved in the QALE-FEM are developed, including the method to move interior nodes, technique to re-distribute the nodes on the free surface, scheme to calculate velocities and so on. The model is validated by water waves generated by a wavemaker in a tank and the interaction between water waves and periodic bars on the bed of tank. Satisfactory agreement is achieved with analytical solutions, experimental data and numerical results from other methods

Enhancing mathematical understanding through real objects: Insights from Tanzanian classrooms

This research investigates the use of real objects and improvisation as learning aids by mathematics teachers in secondary schools within Morogoro Municipality. The study employed a quantitative approach, involving 101 mathematics teachers, to assess the effectiveness of real objects and improvisation in enhancing students' understanding of mathematical concepts. Using a case study research design, the study targeted mathematics teachers in secondary schools in Morogoro Municipality, selected through purposive and convenience sampling. The findings reveal that real objects and improvisation have great potential in enhancing students’ understanding of mathematical concepts. Real objects can be effectively used to reinforce students’ comprehension of mathematics during classroom instruction. They also facilitate easier understanding of mathematical concepts, such as perimeter and area. Additionally, real objects promote student engagement in learning mathematics during lesson delivery and help students bridge the gap between theory and practice. These findings have significant implications for the teaching and learning of mathematics, as they indicate that students become more actively engaged with mathematical concepts, while teachers improve their pedagogical practices in secondary school settings. This study recommends the use of real objects in mathematics classrooms to increase student participation, relate mathematical concepts to students’ daily experiences, and enhance learning outcomes

Performance of Optimization Algorithms in the Model Fitting of the Multi-Scale Numerical Simulation of Ductile Iron Solidification

The use of optimization algorithms to adjust the numerical models with experimental values has been applied in other fields, but the efforts done in metal casting sector are much more limited. The advances in this area may contribute to get metal casting adjusted models in less time improving the confidence in their predictions and contributing to reduce tests at laboratory scale. This work compares the performance of four algorithms (compass search, NEWUOA, genetic algorithm (GA) and particle swarm optimization (PSO)) in the adjustment of the metal casting simulation models. The case study used in the comparison is the multiscale simulation of the hypereutectic ductile iron (SGI) casting solidification. The model fitting criteria is the value of the tensile strength. Four different situations have been studied: model fitting based in 2, 3, 6 and 10 variables. Compass search and PSO have succeeded in reaching the error target in the four cases studied, while NEWUOA and GA have failed in some cases. In the case of the deterministic algorithms, compass search and NEWUOA, the use of a multiple random initial guess has been clearly beneficious.This research was funded by the Basque Government under the ELKARTEK Program (ARGIA Project, ELKARTEK KK-2019/00068) and by the HAZITEK Program (CASTMART Project, HAZITEK ZL-2019/00562)

Pourquoi exposer : les enjeux de l’exposition en bibliothèque

Mémoire de fin d\u27étude du diplôme de conservateur, promotion DCB17, portant sur les expositions en bibliothèque : état des lieux, enjeux, perspectives

WTC2005-63076 THREE-DIMENSIONAL THERMAL FIELD IN SLIDER BEARINGS

ABSTRACT A three dimensional thermohydrodynamic lubrication model which couples the Reynolds and energy equations is developed. The model uses the streamline upwind Petrov-Galerkin (SUPG) method to solve the nonsymmetric stiffness matrix that results from the convective-dominated flow. Model results indicate that the peak temperature is not on the mid-plane surface, a fact that cannot be predicted with two dimensional models. This position shifts towards the mid-plane as the width to length ratio is reduced from ten to one (square slider) as well as when pressure boundary conditions are altered in such a way that the inlet/outlet pressure is higher than the side pressure. The square slider has a peak temperature 4°K less than the wider slider. This is due to the higher side flow in the square slider. INTRODUCTION Slider bearings are widely used in applications such as mechanical seals, plain collar thrust bearings, machine tool guides, and piston rings. They have good load-carrying capacity, excellent stability and durability. Investigation of the thermal effect leads to a better understanding of the load-carrying capacity. Recent studies of thermohydrodynamic lubrication (THDL) slider models include the work of Rodkiewicz [1], Schumack [2], and Kumar et a