Optimal Policies Search for Sensor Management

International audienceThis paper introduces a new approach to solve sensor management problems. Classically sensor management problems can be well formalized as Partially-Observed Markov Decision Processes (POMPD). The original approach developped here consists in deriving the optimal parameterized policy based on a stochastic gradient estimation. We assume in this work that it is possible to learn the optimal policy off-line (in simulation ) using models of the environement and of the sensor(s). The learned policy can then be used to manage the sensor(s). In order to approximate the gradient in a stochastic context, we introduce a new method to approximate the gradient, based on Infinitesimal Perturbation Approximation (IPA). The effectiveness of this general framework is illustrated by the managing of an Electronically Scanned Array Radar. First simulations results are finally proposed

Simulated Impacts of Climate Change on Surface Water Yields over the Sondu Basin in Kenya

Potential impacts of climate change on surface water yields over the Sondu River basin in the western region of Kenya were analysed using the Soil and Water Assessment Tool (SWAT) model with climate input data obtained from the fourth generation coupled Ocean-Atmosphere European Community Hamburg Model (ECHAM4) using the Providing Regional Climates for Impacts Studies (PRECIS) model. Daily time step regional climate scenarios at a spatial grid resolution of 0.44Ëš over the Eastern Africa region were matched to the Sondu river basin and used to calibrate and validate the SWAT model.Analysis of historical and projected rainfall over the basin strongly indicated that the climate of the area will significantly change with wetter climates being experienced by 2030 and beyond. Projected monthly rainfall distribution shows increasing trends in the relatively dry DJF and SON seasons while showing decreasing trends in the relatively wet MAM and JJA seasons. Potential changes in water yields resulting from climate change were computed by comparing simulated yields under climate change scenarios with those simulated under baseline conditions. There was evidence of substantial increases in water yields ranging between 88% and 110% of the baseline yields by 2030 and 2050 respectively. Although simulated water yields are subject to further verification from observed values, this study has provided useful information about potential changes in water yields as a result of climate change over the Sondu River basin and in similar basins in this region

Experimental research of characteristics of shearing ring

Development of passive safety elements represents one of the most complex fields of mechanical engineering and requires practical and theoretical knowledge equally. A new standard EN15227 directed at railway vehicle structures defines the dimensions and phases of deformation of the end-of-vehicle structure during collision. Serbian railways have many passenger wagons over 20 years old that have no crash elements. These wagons are equipped with a standard buffer in accordance with UIC regulations. The challenge, therefore, is to install crash elements in line with the standard buffer as well as to define a moment when the crash element starts energy absorption. A shrinking tube absorber has the most acceptable absorption characteristics as well as being compact and compatible with the dimensions of standard buffer. In this research, the joint between the standard buffer and the collision energy absorber is a shearing ring designed to break in a specific way at a specific force. The standard buffer is designed to withstand a force of 800 kN without permanent deformation. When the force exceeds this value, the spring in the standard buffer is blocked and the shearing ring breaks, activating the energy absorber. The shearing ring is made from quenched and tempered carbon steel that has passed adequate thermal treatment. Dimensioning of the shearing ring required a series of experiments to determine mechanical characteristics using reduced- and full-scale samples. Final verification of dimensions and working principles of shearing ring was done via collision of two passenger coaches

A Modified Real-Time Fault-Tolerant Task Allocation Scheme for Wireless Sensor Networks

In WSNs, the sensor nodes are at risk of failure and malicious attacks (selective forwarding). This may have a profound negative effect when you consider real-time WSNs, making them challenging to deploy. When there is a delay in tasks allocation execution processes in real-time WSNs because of sensor nodes failures, this will cause disastrous consequences if the systems are safety-critical, e.g. aircraft, nuclear power plant, forest fire detection, battlefield monitoring, thus the need to developed a real-time system that is fault-tolerable. This paper developed a modified real-time fault-tolerant task allocation scheme (mRFTAS) for WSNs (wireless sensor networks), using active replication techniques. mRFTAS and RFTAS performance were compared using time of execution of the task, network lifetime and reliability cost. The mRFTAS performance showed an improvement over that of RFTAS when it comes to reducing the time it takes for task execution by 45.56% and reliability cost of 7.99% while prolonging the network lifetime by 36.35%

The effect of axial load on the sagittal plane curvature of the upright human spine in vivo

Copyright © 2008 Elsevier. NOTICE: this is the author’s version of a work that was accepted for publication in Pattern Recognition . Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Journal of Biomechanics, Vol. 41 Issue 13 (2008), DOI: 10.1016/j.jbiomech.2008.06.035Determining the effect of load carriage on the human spine in vivo is important for determining spinal forces and establishing potential mechanisms of back injury. Previous studies have suggested that the natural curvature of the spine straightens under load, but are based on modelling and external measurements from the surface of the back. In the current study, an upright positional MRI scanner was used to acquire sagittal images of the lumbar and lower thoracic spine of 24 subjects. The subjects were imaged in standing whilst supporting 0, 8 and 16 kg of load which was applied axially across the shoulders using an apron. An active shape model of the vertebral bodies from T10 to S1 was created and used to characterise the effect of load. The results from the shape model showed that the behaviour of the average-shaped spine was to straighten slightly. However, the shape model also showed that the effect of load exhibited systematic variation between individuals. Those who had a smaller than average curvature before loading straightened under load, whereas those who had a greater than average curvature before loading showed an increase in curvature under load. The variation in behaviour of differently shaped spines may have further implications for the effects of load in lifting manoeuvres and in understanding the aetiology of back pain

Science and Ideology in Economic, Political, and Social Thought

This paper has two sources: One is my own research in three broad areas: business cycles, economic measurement and social choice. In all of these fields I attempted to apply the basic precepts of the scientific method as it is understood in the natural sciences. I found that my effort at using natural science methods in economics was met with little understanding and often considerable hostility. I found economics to be driven less by common sense and empirical evidence, then by various ideologies that exhibited either a political or a methodological bias, or both. This brings me to the second source: Several books have appeared recently that describe in historical terms the ideological forces that have shaped either the direct areas in which I worked, or a broader background. These books taught me that the ideological forces in the social sciences are even stronger than I imagined on the basis of my own experiences. The scientific method is the antipode to ideology. I feel that the scientific work that I have done on specific, long standing and fundamental problems in economics and political science have given me additional insights into the destructive role of ideology beyond the history of thought orientation of the works I will be discussing

Continued availability and sale of pangolins in a major urban bushmeat market in Cameroon despite national bans and the COVID-19 outbreak

First paragraph: Bushmeat (or ‘wild meat’, defined as the meat of wild animals) is a major source of protein for rural people across sub-Saharan Africa (Ingram et al., 2021), yet some species suffer unsustainable levels of exploitation often to meet the demands of increasing urban populations (Coad et al., 2019; Wilkie et al., 2016). As in the rest of Central Africa, Cameroon has a long history of bushmeat consumption and trade (Bahuchet & Ioveva, 1999; Randolph, 2016). Pangolins (Family: Manidae) have been one of the many groups of species exploited as they are highly valued for food and, in some countries, used as traditional remedies (Soewu et al., 2020). Pangolin meat is favoured for its taste and it remains commonly offered for sale in Cameroonian markets and restaurants (Ingram et al., 2018; Nguyen et al., 2021). Furthermore, Cameroon has become one of the major export countries for the illegal trade in pangolin scales from Africa to Asia (Ingram et al., 2019a), to supply the market for Asian traditional medicines, for example in traditional Chinese medicine (Wang et al., 2020). All African pangolin species are now considered to have declining population trends (Ingram et al., 2019b; Nixon et al., 2019; Pietersen et al., 2019a, 2019b)

The contribution of geogenic particulate matter to lung disease in indigenous children

© 2019 by the authors. Licensee MDPI, Basel, Switzerland. Indigenous children have much higher rates of ear and lung disease than non-Indigenous children, which may be related to exposure to high levels of geogenic (earth-derived) particulate matter (PM). The aim of this study was to assess the relationship between dust levels and health in Indigenous children in Western Australia (W.A.). Data were from a population-based sample of 1077 Indigenous children living in 66 remote communities of W.A. (>2,000,000 km2), with information on health outcomes derived from carer reports and hospitalisation records. Associations between dust levels and health outcomes were assessed by multivariate logistic regression in a multi-level framework. We assessed the effect of exposure to community sampled PM on epithelial cell (NuLi-1) responses to non-typeable Haemophilus influenzae (NTHi) in vitro. High dust levels were associated with increased odds of hospitalisation for upper (OR 1.77 95% CI [1.02–3.06]) and lower (OR 1.99 95% CI [1.08–3.68]) respiratory tract infections and ear disease (OR 3.06 95% CI [1.20–7.80]). Exposure to PM enhanced NTHi adhesion and invasion of epithelial cells and impaired IL-8 production. Exposure to geogenic PM may be contributing to the poor respiratory health of disadvantaged communities in arid environments where geogenic PM levels are high