Cross-layer framework and optimization for efficient use of the energy budget of IoT Nodes

Both physical and MAC-layer need to be jointly optimized to maximize the autonomy of IoT devices. Therefore, a cross-layer design is imperative to effectively realize Low Power Wide Area networks (LPWANs). In the present paper, a cross-layer assessment framework including power modeling is proposed. Through this simulation framework, the energy consumption of IoT devices, currently deployed in LoRaWAN networks, is evaluated. We demonstrate that a cross-layer approach significantly improves energy efficiency and overall throughput. Two major contributions are made. First, an open-source LPWAN assessment framework has been conceived. It allows testing and evaluating hypotheses and schemes. Secondly, as a representative case, the LoRaWAN protocol is assessed. The findings indicate how a cross-layer approach can optimize LPWANs in terms of energy efficiency and throughput. For instance, it is shown that the use of larger payloads can reduce up to three times the energy consumption on quasi-static channels yet may bring an energy penalty under adverse dynamic conditions

Structure and Evolution of the Envelopes of Deeply Embedded Massive Young Stars

The physical structure of the envelopes around a sample of fourteen massive (1000-100,000 solar L) young stars is investigated on 100- 100,000 AU scales using maps and spectra in submillimeter continuum and lines of C17O, CS and H2CO. The total column densities and the temperature profiles are obtained by fitting self-consistent dust models to submillimeter photometry. Both the molecular line and dust emission data indicate density gradients ~r^{-alpha}, with alpha=1.0-1.5, significantly flatter than the alpha=2.0 generally found for low-mass objects. This flattening may indicate that in massive young stellar objects, nonthermal pressure is more important for the support against gravitational collapse, while thermal pressure dominates for low-mass sources. We find alpha=2 for two hot core-type sources, but regard this as an upper limit since in these objects, the CS abundance may be enhanced in the warm gas close to the star.Comment: To be published in The Astrophysical Journal. 54 pages including 14 figures Revised version with references adde

The spatial distribution of excited H_2 in T Tau: a molecular outflow in a young binary system

Strong extended emission from molecular hydrogen in the v = 1 → 0 S(l) transition is mapped around T Tau. In addition, the v = 2 → 1 S(l) line is detected close to the star. The ratio of the two transitions is consistent with an excitation process in which both fluorescence by stellar ultraviolet radiation and collisions in a warm, dense medium play a role. The morphology is interpreted as emission from a molecular outflow which appears to wiggle as a result of the fact that T Tau is a binary system seen almost pole-on. It is shown that an outflow with a small opening angle can reproduce the observed extended emission. From comparison with previous studies it is argued that the molecular outflow originates from T Tau S, the infrared component. The presented model constrains the orientation and geometry of the system

Bargaining power and segmented markets:Evidence from rental and owner-occupied housing

In segmented markets for heterogeneous goods, prices reflect a mixture of demand for characteristics, bargaining power and market segmentation. This paper integrates bargaining into the search model to investigate bargaining for housing across investors and owner-occupiers when the investment housing segment is also subject to a rental property discount. It provides a framework for empirically identifying separate price effects of property type and bargaining power. We exploit homestead exemption information to empirically identify sellers and buyers as investors or owner-occupiers. Data from Orange County, Florida, over 2000-2012, show a greater rental discount when controlling for investor bargaining power than when estimated in the conventional manner. In addition, investor relative bargaining power is not the same when selling to an owner-occupier as when buying from an owner-occupier. The results are robust across market phases and across neighborhoods

The Impact of the Massive Young Star GL 2591 on its Circumstellar Material: Temperature, Density and Velocity Structure

The temperature, density and kinematics of the gas and dust surrounding the luminous young stellar object GL~2591 are investigated on scales as small as 100 AU, probed by 4.7 micron absorption spectroscopy, to over 60,000 AU, probed by single-dish submillimeter spectroscopy. These two scales are connected by interferometric 86-226 GHz images of size 60,000 AU and resolution 2000 AU in continuum and molecular lines. The data are used to constrain the physical structure of the envelope and investigate the influence of the young star on its immediate surroundings.Comment: To be published in The Astrophysical Journal, Vol. 522 No. 2 (1999 Sep 10). 45 pages including 11 figure

The price of ignorance:foreclosures, uninformed buyers and house prices

Uninformed buyers may pay more when purchasing complex assets, such as houses. This paper compares local house buyers who are later foreclosed with those not foreclosed for various buyer-types, namely, owner-occupier households, investor-companies, second-home buyers, and small-scale investors. Data from one of the foreclosure epicenters, Orange County, Florida, reveal that subsequent foreclosures are associated with higher prices for comparable housing at the time of purchase. The premium paid by buyers between 2000 and 2007 who experience foreclosure after 2007 is larger closer to the 2007 market peak, approaching 3 percent. We find considerable heterogeneity across buyer-types. In particular, foreclosed second-home buyers and small-scale investors systematically pay more, while investor-companies and owneroccupiers do not. The pattern is consistent with the hypothesis that the premium paid by foreclosed households reflects poor information or limited financial acumen

Rags to Riches and Conflict on the Playground: Contrasting Narratives of E-Learning in an Educational Faculty

We have argued before that personal learning experiences and, to a degree, the teaching experiences of lecturers could be seen as directive indicators of their e-learning uptake. We have also proposed that their \u27narrative situatedness\u27 is where we believe reasoning about engagement with educational technology can be found. Through narrative analysis of a number of interviews conducted with lecturers we have identified contrasting \u27stories\u27 from two lecturers who started out using technology in their teaching at around about the same time within an Education Faculty. These two narratives provide insight into why the one lecturer (Ellen) succeeded in her e-learning endeavours and why Rose has not yet managed to change her fundamental ideas about teaching and knowledge in any significant way. These two narratives are presented in this paper to expose these lecturer\u27s unique and contrasting \u27cultural worlds\u27 and shed light on issues that may not have emerged through other methods

Annular Vortex Solutions to the Landau-Ginzburg Equations in Mesoscopic Superconductors

New vortex solutions to the Landau-Ginzburg equations are described. These configurations, which extend the well known Abrikosov and giant magnetic vortex ones, consist of a succession of ring-like supercurrent vortices organised in a concentric pattern, possibly bound to a giant magnetic vortex then lying at their center. The dynamical and thermodynamic stability of these annular vortices is an important open issue on which hinges the direct experimental observation of such configurations. Nevertheless, annular vortices should affect indirectly specific dynamic properties of mesoscopic superconducting devices amenable to physical observation.Comment: 12 pages, LaTeX, 2 Postscript figure

The role of physical and mental multimorbidity in suicidal thoughts and behaviours in a Scottish population cohort study

Background: Physical illness and mental disorders play a significant role in fatal and non-fatal suicidal behaviour. However, there is no clear evidence for the effect of physical and mental illness co-occurrence (multimorbidity) in suicidal ideation and attempts. The aim of the current study was to investigate, whether physical/mental health multimorbidity predicted suicidal thoughts and behaviours as outcomes. Methods: Data from the West of Scotland Twenty-07 cohort were analysed. Twenty-07 is a multiple cohort study following people for 20 years, through five waves of data collection. Participants who responded to past-year suicidal thoughts and suicide attempt items were grouped into four distinct health-groups based on having: (1) neither physical nor mental health condition (controls); (2) one or more physical health condition; (3) one or more mental health condition and; (4) multimorbidity. The role of multimorbidity in predicting suicidal ideation and suicide attempts was tested with a generalised estimating equation (GEE) model and odds ratios (ORs) and 95% CIs are presented. Whether the effect of multimorbidity was stronger than either health condition alone was also assessed. Results: Multimorbidity had a significant effect on suicidal thoughts and suicide attempts, compared to the control group, but was not found to increase the risk of either suicide-related outcomes, more than mental illness alone. Conclusions: We identified an effect of physical/mental multimorbidity on risk of suicidal thoughts and suicide attempts. Considering that suicide and related behaviour are rare events, future studies should employ a prospective design on the role of multimorbidity in suicidality, employing larger dataset