Maximum isometric finger pull forces

The current study determined the maximal voluntary isometric forces for a variety of finger pulling tasks. Twenty healthy females, with no history of upper extremity injuries, were asked to use the fingers from their dominant hands and apply their maximal voluntary pull forces for seven conditions that varied in the number of fingers, force application location and interface characteristics. All conditions were tested with and without the use of a glove. However, there was no significant effect of wearing a glove. As expected, the maximum force increased with the number of fingers used and decreased when forces were applied on the finger tip instead of the first distal inter-phalangeal joint. Maximum forces ranged from 59.5 ± 21.4 N when using the index finger tip on a thin ring, to 268.7 ± 77.2 N when using all four fingers on a straight bar.

Relevance to industry

Many industrial tasks require pulling with the finger(s). The current study provides a set of maximal finger pull force values that can be used to set force limits that will contribute to protecting worker health and safety and insuring manufacturing quality.     

Makespan minimisation for a parallel machine scheduling problem with preemption and job incompatibility

In this paper, an extension of the graph colouring problem is introduced to model a parallel machine scheduling problem with job incompatibility. To get closer to real-world applications, where the number of machines is limited and jobs have different processing times, each vertex of the graph requires multiple colours and the number of vertices with the same colour is bounded. In addition, several objectives related to scheduling are considered: makespan, number of pre-emptions and summation over the jobs’ throughput times. Different solution methods are proposed, namely, two greedy heuristics, two tabu search methods and an adaptive memory algorithm. The latter uses multiple recombination operators, each one being designed for optimising a subset of objectives. The most appropriate operator is selected dynamically at each iteration, depending on its past performance. Experiments show that the proposed algorithm is effective and robust, while providing high-quality solutions on benchmark instances for the graph multi-colouring problem, a simplification of the considered problem.     

Catalytic reduction of nitrogen monoxide by propene in the presence of excess oxygen over gold based ceria catalyst

The catalytic reduction of nitrogen monoxide by propene in the presence of excess oxygen over gold based ceria catalyst was studied. Adsorption and temperature programmed desorption of NO/O₂ on Au/CeO₂ reveal that the catalyst adsorbs and desorbs NO over a large range of temperature. A maximum of 26% conversion of NO _x was obtained around 210 °C, with a selectivity of 50% to N₂.     

Portrait des différences entre les genres dans le contexte de l'apprentissage de l'électricité en fonction de la certitude exprimée lors de la production de réponses

Abstract

This exploratory research aims to describe changes in the “feeling-of-knowing” (FOK) experienced by high school students who are being introduced to the fundamental concepts of electricity through learning by discovery. The analysis focuses first on the initial state of boys and girls in terms of their prior experience and the perception they have of their abilities in science and technology, then on the change in their performance (i.e. the conceptual shifts that take place) and the FOK of these same groups as they participate in “electronic problem-solving” activities. The results seem to indicate that this pedagogical approach produces the same results among both sexes in terms of learning acquisition, but favors boys in terms of the certainty they have of the solutions they provide.     

Social support network evolution after the birth of their first baby: comparison between lower and middle class mothers

The social support networks of a group of low socio-economic status (S.E.S.) mothers (n = 87) and a group of higher S.E.S. mothers (n = 44) are described and compared at the 30th week of pregnancy and at the third week after the birth of their first baby. The evolution of the support networks for these two groups of mothers during this period is also examined. A modified form of the ASSIS from Barrera has been used to measure the social support network. Results show that, during pregnancy, the social support network of low-S.E.S. mothers is more restricted than that of higher S.E.S. mothers. Although the actual number of people around them after the birth of the baby did not increase, low-S.E.S. mothers said they felt a slight increase in the number of people available to give support in some way. They also reported that conflicts were more frequent with some of them. For higher S.E.S. mothers, all social network variables remained stable from pregnancy through the first postpartum month.     

Multidirectional manual arm strength and its relationship with resultant shoulder moment and arm posture

Previous work has quantified manual force capabilities for ergonomics design, but the number of studies and range of conditions tested are limited in scope. Therefore, the aims of this study were to collect seated manual arm strength (MAS) data from 24 females in several unique exertion directions (n = 26) and hand locations relative to the shoulder (n = 8), and to investigate the associations between MAS and shoulder/elbow moments. MAS was generally highest when the direction of force application was oriented parallel to the vector from the shoulder to knuckle, and weakest when oriented orthogonal to that vector. Moderate correlations were found between MAS and: (1) resultant shoulder moment (r = 0.34), (2) resultant moment arms (r = ?0.545) and (3) elbow flexion/extension moment (r = 0.481). Our strength data will be used in the development of a comprehensive MAS predictive method, so that strength capabilities can be predicted to help design acceptable tasks in the workplace.

Practitioner Summary: This study sought to enhance our understanding of one-handed manual arm strength capabilities for ergonomics task evaluations. Our findings provide researchers and practitioners with manual strength data for off-axis force directions, as well as hand locations not previously measured. These data will contribute to future methods for predicting strength capabilities.     

Optimizing profits from hydroelectricity production

This paper presents a deterministic and a stochastic mathematical model for maximizing the profits obtained by selling electricity produced through a cascade of dams and reservoirs in a deregulated market. The first model is based on deterministic electricity prices while the other integrates price stochasticity through the management of a tree of potential price scenarios. Numerical results based on historical data demonstrate the superiority of the stochastic model over the deterministic one. It is also shown that price volatility impacts the profits obtained by the stochastic model.     

Passive versus active engulfment: verdict from trajectory simulations of lunge-feeding fin whales Balaenoptera physalus

Lunge-feeding in rorqual whales represents the largest biomechanical event on Earth and one of the most extreme feeding methods among aquatic vertebrates. By accelerating to high speeds and by opening their mouth to large gape angles, these whales generate the water pressure required to expand their mouth around a large volume of prey-laden water. Such large influx is facilitated by highly extensible ventral groove blubber (VGB) associated with the walls of the throat (buccal cavity). Based on the mechanical properties of this tissue, previous studies have assumed lunge-feeding to be an entirely passive process, where the flow-induced pressure driving the expansion of the VGB is met with little resistance. Such compliant engulfment would be facilitated by the compliant properties of the VGB that have been measured on dead specimens. However, adjoining the ventral blubber are several layers of well-developed muscle embedded with mechanoreceptors, thereby suggesting a capability to gauge the magnitude of engulfed water and use eccentric muscle action to control the flux of water into the mouth. An unsteady hydrodynamic model of fin whale lunge-feeding is presented here to test whether engulfment is exclusively passive and compliant or involves muscle action. The model is based on the explicit simulation of the engulfed water as it interacts with the buccal cavity walls of the whale, under different heuristically motivated cavity forces. Our results, together with their comparison with velocity data collected in the field, suggest that adult rorquals actively push engulfed water forward from the very onset of mouth opening in order to successfully complete a lunge. Interestingly, such an action involves a reflux of the engulfed mass rather than the oft-assumed rebound, which would occur mainly at the very end of a lunge sequence dominated by compliant engulfment. Given the great mass of the engulfed water, reflux creation adds a significant source of hydrodynamic drag to the lunge process, but with the benefit of helping to circumvent the problem of removing prey from baleen by enhancing the efficiency of cross-flow filtration after mouth closing. Reflux management for a successful lunge will therefore demand well-coordinated muscular actions of the tail, mouth and ventral cavity.