Internal stresses in steel plate generated by shape memory alloy inserts

Neutron strain scanning was employed to investigate the internal stress fields in steel plate coupons with embedded prestrained superelastic NiTi shape memory alloy inserts. Strain fields in steel were evaluated at T = 21 °C and 130 °C on virgin coupons as well as on mechanically and thermally fatigued coupons. Internal stress fields were evaluated by direct calculation of principal stress components from the experimentally measured lattice strains as well as by employing an inverse finite element modeling approach. It is shown that if the NiTi inserts are embedded into the elastic steel matrix following a carefully designed technological procedure, the internal stress fields vary with temperature in a reproducible and predictable way. It is estimated that this mechanism of internal stress generation can be safely applied in the temperature range from −20 °C to 150 °C and is relatively resistant to thermal and mechanical fatigue. The predictability and fatigue endurance of the mechanism are of essential importance for the development of future smart metal matrix composites or smart structures with embedded shape memory alloy components

On the late northward propagation of the West African monsoon in summer 2006 in the region of Niger/Mali

International audienceThis paper investigates the fine-scale dynamical processes at the origin of the late northward migration of the monsoon flow in summer 2006 in the region of Niger and Mali (onset on 3 July 2006 compared to the climatological onset date, 24 June). Compared to a 28-year climatology, 2006 NCEP-2 reanalyses show evidence of an anomalous pattern during 10 days between 25 June and 3 July 2006, characterized by the African Easterly Jet (AEJ) blowing from the northeast along a narrow northeast/southwest band located over the Hoggar and Air mountains associated with an unusually strong northeasterly harmattan in the lee of the mountains. Using data collected during the African Monsoon Multidisciplinary Analysis (AMMA) experiment and mesoscale numerical simulations, this study shows evidence of interaction between the AEJ and the orography supported by the reduced gravity shallow water theory which explains the enhancement of the harmattan downstream of the Hoggar and Air mountains in summer 2006. The enhanced harmattan contributes to move southward the intertropical discontinuity (ITD) defined as the interface between the cool moist southwesterly monsoon flow and the warm dry harmattan. Finally, an interaction between the ITD and African Easterly waves contributes to propagate the ITD southward retreat about 1500 km to the west of the Hoggar and Air mountains

Health Status and Self-care Outcomes After an Education-Support Intervention for People with Chronic Heart Failure

BACKGROUND: The rising cost of hospitalizations for heart failure (HF) care mandates intervention models to address education for self-care success. The effectiveness of memory enhancement strategies to improve self-care and learning needs further examination. OBJECTIVE: The objective of this study was to examine the effects of an education-support intervention delivered in the home setting, using strategies to improve health status and self-care in adults/older adults with class I to III HF. Our secondary purpose was to explore participants\u27 subjective perceptions of the intervention. METHODS: This study used a randomized, 2-group design. Fifty people were enrolled for 9 months and tested at 4 time points-baseline; after a 3-month education-support intervention; at 6 months, after 3 months of telephone/e-mail support; and 9 months, after a 3-month period of no contact. Advanced practice registered nurses delivered the intervention. Memory enhancement methods were built into the teaching materials and delivery of the intervention. We measured the intervention\u27s effectiveness on health status outcomes (functional status, self-efficacy, quality of life, emotional state/depressive symptoms, and metamemory) and self-care outcomes (knowledge/knowledge retention, self-care ability). Subjects evaluated the usefulness of the intervention at the end of the study. RESULTS: The mean age of the sample was 62.4 years, with a slight majority of female participants. Participants were well educated and had other concomitant diseases, including diabetes (48%) and an unexpected degree of obesity. The intervention group showed significant improvements in functional status, self-efficacy, and quality of life (Kansas City Cardiomyopathy Questionnaire); metamemory Change and Capacity subscales (Metamemory in Adulthood Questionnaire); self-care knowledge (HF Knowledge Test); and self-care (Self-care in Heart Failure Index). Participants in both groups improved in depressive scores (Geriatric Depression Scale). CONCLUSIONS: An in-home intervention delivered by advanced practice registered nurses was successful in several health status and self-care outcomes, including functional status, self-efficacy, quality of life, metamemory, self-care status, and HF knowledge

ON THE INTERACTION BETWEEN SEA BREEZE AND SUMMER MISTRAL AT THE EXIT OF THE RHÔNE VALLEY DURING THE ESCOMPTE EXPERIMENT

The abstract investigates experimentally and numerically the structure of a combined Mistral sea breeze event at the exit of the Rhône valley in southeastern France, as well as the near shoreline water variability at the alternation between the Mistral and the sea breeze

Between supply and demand: the limits to participatory development in South Africa

Much of the focus in the literature on participatory development has been on the demand side and on the extent to which citizens succeed in pressuring the state to deliver basic services. Less attention has been focused on the supply side of participatory development, namely on how state institutions give effect to development policies. Post-Apartheid South Africa is replete with policies and legislation supporting participatory processes and yet in practice this has seldom lived up to the ideals espoused. This article examines the delivery of public housing in poor communities in three municipalities in South Africa and argues that there is a mismatch between how the formulators of policy understand participation and how it is interpreted by beneficiary communities and local officials. It concludes that considerably more attention needs to be focused on why officials fail to translate national policies into action if participatory democracy is to attain any legitimacy in the population at large.Web of Scienc

Stretching and squeezing of sessile dielectric drops by the optical radiation pressure

We study numerically the deformation of sessile dielectric drops immersed in a second fluid when submitted to the optical radiation pressure of a continuous Gaussian laser wave. Both drop stretching and drop squeezing are investigated at steady state where capillary effects balance the optical radiation pressure. A boundary integral method is implemented to solve the axisymmetric Stokes flow in the two fluids. In the stretching case, we find that the drop shape goes from prolate to near-conical for increasing optical radiation pressure whatever the drop to beam radius ratio and the refractive index contrast between the two fluids. The semi-angle of the cone at equilibrium decreases with the drop to beam radius ratio and is weakly influenced by the index contrast. Above a threshold value of the radiation pressure, these "optical cones" become unstable and a disruption is observed. Conversely, when optically squeezed, the drop shifts from an oblate to a concave shape leading to the formation of a stable "optical torus". These findings extend the electrohydrodynamics approach of drop deformation to the much less investigated "optical domain" and reveal the openings offered by laser waves to actively manipulate droplets at the micrometer scale

Laser microfluidics: fluid actuation by light

The development of microfluidic devices is still hindered by the lack of robust fundamental building blocks that constitute any fluidic system. An attractive approach is optical actuation because light field interaction is contactless and dynamically reconfigurable, and solutions have been anticipated through the use of optical forces to manipulate microparticles in flows. Following the concept of an 'optical chip' advanced from the optical actuation of suspensions, we propose in this survey new routes to extend this concept to microfluidic two-phase flows. First, we investigate the destabilization of fluid interfaces by the optical radiation pressure and the formation of liquid jets. We analyze the droplet shedding from the jet tip and the continuous transport in laser-sustained liquid channels. In the second part, we investigate a dissipative light-flow interaction mechanism consisting in heating locally two immiscible fluids to produce thermocapillary stresses along their interface. This opto-capillary coupling is implemented in adequate microchannel geometries to manipulate two-phase flows and propose a contactless optical toolbox including valves, droplet sorters and switches, droplet dividers or droplet mergers. Finally, we discuss radiation pressure and opto-capillary effects in the context of the 'optical chip' where flows, channels and operating functions would all be performed optically on the same device