447 research outputs found
Internet of things
Manual of Digital Earth / Editors: Huadong Guo, Michael F. Goodchild, Alessandro Annoni .- Springer, 2020 .- ISBN: 978-981-32-9915-3Digital Earth was born with the aim of replicating the real world within the digital world. Many efforts have been made to observe and sense the Earth, both from space (remote sensing) and by using in situ sensors. Focusing on the latter, advances in Digital Earth have established vital bridges to exploit these sensors and their networks by taking location as a key element. The current era of connectivity envisions that everything is connected to everything. The concept of the Internet of Things(IoT)emergedasaholisticproposaltoenableanecosystemofvaried,heterogeneous networked objects and devices to speak to and interact with each other. To make the IoT ecosystem a reality, it is necessary to understand the electronic components, communication protocols, real-time analysis techniques, and the location of the objects and devices. The IoT ecosystem and the Digital Earth (DE) jointly form interrelated infrastructures for addressing todayâs pressing issues and complex challenges. In this chapter, we explore the synergies and frictions in establishing an efïŹcient and permanent collaboration between the two infrastructures, in order to adequately address multidisciplinary and increasingly complex real-world problems. Although there are still some pending issues, the identiïŹed synergies generate optimism for a true collaboration between the Internet of Things and the Digital Earth
Simulations of Aerodynamic Damping for MEMS Resonators
Aerodynamic damping for MEMS resonators is studied based on the numerical solution of Boltzmann-ESBGK equation. A compact model is then developed based on numerical simulations for a wide range of Knudsen numbers. The damping predictions are compared with both Reynold equation based models and several sets of experimental data. It has been found that the structural damping is dominant at low pressures (high Knudsen numbers). For cases with small length-to-width ratios and large vibration amplitudes, the threedimensionality effects must be taken into account. Finally, an uncertainty quantification approach based on the probability transformation method has been applied to assess the influence of pressure and geometric uncertainties. The output probability density functions (PDF) of the damping ratio has been studied for various input PDF of beam geometry and ambient pressure
Magnetoconductivity of quantum wires with elastic and inelastic scattering
We use a Boltzmann equation to determine the magnetoconductivity of quantum
wires. The presence of a confining potential in addition to the magnetic field
removes the degeneracy of the Landau levels and allows one to associate a group
velocity with each single-particle state. The distribution function describing
the occupation of these single-particle states satisfies a Boltzmann equation,
which may be solved exactly in the case of impurity scattering. In the case
where the electrons scatter against both phonons and impurities we solve
numerically - and in certain limits analytically - the integral equation for
the distribution function, and determine the conductivity as a function of
temperature and magnetic field. The magnetoconductivity exhibits a maximum at a
temperature, which depends on the relative strength of the impurity and
electron-phonon scattering, and shows oscillations when the Fermi energy or the
magnetic field is varied.Comment: 21 pages (revtex 3.0), 5 postscript figures available upon request at
[email protected] or [email protected]
The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies
We performed a 4.5-month multi-instrument campaign (from radio to VHE gamma
rays) on Mrk421 between January 2009 and June 2009, which included VLBA,
F-GAMMA, GASP-WEBT, Swift, RXTE, Fermi-LAT, MAGIC, and Whipple, among other
instruments and collaborations. Mrk421 was found in its typical (non-flaring)
activity state, with a VHE flux of about half that of the Crab Nebula, yet the
light curves show significant variability at all wavelengths, the highest
variability being in the X-rays. We determined the power spectral densities
(PSD) at most wavelengths and found that all PSDs can be described by
power-laws without a break, and with indices consistent with pink/red-noise
behavior. We observed a harder-when-brighter behavior in the X-ray spectra and
measured a positive correlation between VHE and X-ray fluxes with zero time
lag. Such characteristics have been reported many times during flaring
activity, but here they are reported for the first time in the non-flaring
state. We also observed an overall anti-correlation between optical/UV and
X-rays extending over the duration of the campaign.
The harder-when-brighter behavior in the X-ray spectra and the measured
positive X-ray/VHE correlation during the 2009 multi-wavelength campaign
suggests that the physical processes dominating the emission during non-flaring
states have similarities with those occurring during flaring activity. In
particular, this observation supports leptonic scenarios as being responsible
for the emission of Mrk421 during non-flaring activity. Such a temporally
extended X-ray/VHE correlation is not driven by any single flaring event, and
hence is difficult to explain within the standard hadronic scenarios. The
highest variability is observed in the X-ray band, which, within the one-zone
synchrotron self-Compton scenario, indicates that the electron energy
distribution is most variable at the highest energies.Comment: Accepted for publication in A&A, 18 pages, 14 figures (v2 has a small
modification in the acknowledgments, and also corrects a typo in the field
"author" in the metadata
The Kuiper Belt and Other Debris Disks
We discuss the current knowledge of the Solar system, focusing on bodies in
the outer regions, on the information they provide concerning Solar system
formation, and on the possible relationships that may exist between our system
and the debris disks of other stars. Beyond the domains of the Terrestrial and
giant planets, the comets in the Kuiper belt and the Oort cloud preserve some
of our most pristine materials. The Kuiper belt, in particular, is a
collisional dust source and a scientific bridge to the dusty "debris disks"
observed around many nearby main-sequence stars. Study of the Solar system
provides a level of detail that we cannot discern in the distant disks while
observations of the disks may help to set the Solar system in proper context.Comment: 50 pages, 25 Figures. To appear in conference proceedings book
"Astrophysics in the Next Decade
The impact of Curtin University's Activity, Food and Attitudes Program on physical activity, sedentary time and fruit, vegetable and junk food consumption among overweight and obese adolescents: A waitlist controlled trial
Background: To determine the effects of participation in Curtin University's Activity, Food and Attitudes Program (CAFAP), a community-based, family-centered behavioural intervention, on the physical activity, sedentary time, and healthy eating behaviours of overweight and obese adolescents. Methods: In this waitlist controlled clinical trial in Western Australia, adolescents (n = 69, 71% female, mean age 14.1 (SD 1.6) years) and parents completed an 8-week intervention followed by 12 months of telephone and text message support. Assessments were completed at baseline, before beginning the intervention, immediately following the intervention, and at 3-, 6-, and 12- months follow-up. The primary outcomes were physical activity and sedentary time assessed by accelerometers and servings of fruit, vegetables and junk food assessed by 3-day food records. Results: During the intensive 8-week intervention sedentary time decreased by â5.1 min/day/month (95% CI: â11.0, 0.8) which was significantly greater than the rate of change during the waitlist period (p = .014). Moderate physical activity increased by 1.8 min/day/month (95% CI: â0.04, 3.6) during the intervention period, which was significantly greater than the rate of change during the waitlist period (p = .041). Fruit consumption increased during the intervention period (monthly incidence rate ratio (IRR) 1.3, 95% CI: 1.10, 1.56) and junk food consumption decreased (monthly IRR 0.8, 95% CI: 0.74, 0.94) and these changes were different to those seen during the waitlist period (p = .004 and p = .020 respectively). Conclusions: Participating in CAFAP appeared to have a positive influence on the physical activity, sedentary and healthy eating behaviours of overweight and obese adolescents and many of these changes were maintained for one year following the intensive intervention. Trial Registration: Australia and New Zealand Clinical Trials Registry ACTRN12611001187932
Michael Goveâs war on professional historical expertise : conservative curriculum reform, extreme Whig history and the place of imperial heroes in modern multicultural Britain
Six years of continuously baiting his opponents within the history profession eventually amounted to little where it mattered most. UK Secretary of State for Education, Michael Gove, finally backtracked in 2013 on his plans to impose a curriculum for English schools based on a linear chronology of the achievements of British national heroes. His âhistory as celebrationâ curriculum was designed to instil pride amongst students in a supposedly shared national past, but would merely have accentuated how many students in modern multicultural Britain fail to recognise themselves in what is taught in school history lessons. Now that the dust has settled on Goveâs tenure as Secretary of State, the time is right for retrospective analysis of how his plans for the history curriculum made it quite so far. How did he construct an âideologicalâ conception of expertise which allowed him to go toe-to-toe for so long with the âprofessionalâ expertise of academic historians and history teachers? What does the content of this ideological expertise tell us about the politics of race within Conservative Party curriculum reforms? This article answers these questions to characterise Gove as a âwhig historianâ of a wilfully extreme nature in his attachment to imperial heroes as the best way to teach national history in modern multicultural Britain
Temperature-ramped 129Xe spin-exchange optical pumping
We describe temperature-ramped spin-exchange optical pumping (TR-SEOP) in an automated high-throughput batch-mode 129Xe hyperpolarizer utilizing three key temperature regimes: (i) âhotâwhere the 129Xe hyperpolarization rate is maximal, (ii) âwarmâ-where the 129Xe hyperpolarization approaches unity, and (iii) âcoolâ where hyperpolarized 129Xe gas is transferred into a Tedlar bag with low Rb content (<5 ng per âŒ1 L dose) suitable for human imaging applications. Unlike with the conventional approach of batch-mode SEOP, here all three temperature regimes may be operated under continuous high-power (170 W) laser irradiation, and hyperpolarized 129Xe gas is delivered without the need for a cryocollection step. The variable-temperature approach increased the SEOP rate by more than 2-fold compared to the constant-temperature polarization rate (e.g., giving effective values for the exponential buildup constant ÎłSEOP of 62.5 ± 3.7 Ă 10â3 minâ1 vs 29.9 ± 1.2 Ă 10â3 minâ1) while achieving nearly the same maximum %PXe value (88.0 ± 0.8% vs 90.1% ± 0.8%, for a 500 Torr (67 kPa) Xe cell loadingcorresponding to nuclear magnetic resonance/magnetic resonance imaging (NMR/MRI) enhancements of âŒ3.1 Ă 105 and âŒ2.32 Ă 108 at the relevant fields for clinical imaging and HP 129Xe production of 3 T and 4 mT, respectively); moreover, the intercycle âdeadâ time was also significantly decreased. The higher-throughput TR-SEOP approach can be implemented without sacrificing the level of 129Xe hyperpolarization
or the experimental stability for automation-making this approach beneficial for improving the overall 129Xe production rate in clinical settings
Exposing the Contradictory Claims, Myths and Illusions of the âSecrets of Business Success and Company LongevityĂ¹ùâÂŹ Genre
Over the last three decades, several management consultants, academics and business practitioners have laid claim to identifying âthe secretsĂ¹ùâÂŹ of business success and company longevity. However, a systematic analysis of 24 studies in this genre revealed fundamental disagreements over the elements these authors claim are the primary drivers of business performance and longevity, and demonstrates that they share eight methodological and analytical flaws. Furthermore, many of the claims they made about âthe secretsĂ¹ùâÂŹ of business success have not stood the test of time. The paper explains why business practitioners will find little in these studies to help their companies become more successful now and in the future, and also speculates why several of these studies became international best-sellers during the 1980s, 1990s and 2000s. It concludes by suggesting some new avenues for future research in this domain, and highlights the practical implications of these findings for business practitioners
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