To help allies, send security guarantees, not nuclear bombs

Despite the end of the Cold War more than two decades ago, the U.S. still deploys nuclear weapons in several countries. But does deploying these weapons act as a deterrent to conflict, making these countries safer? In new research which analyses the effects of such nuclear deployments, Matthew Fuhrmann and Todd S. Sechser find that their presence does little, when compared with alliance guarantees. They write that having an alliance with a nuclear armed ally is actually more effective in preventing armed conflicts than the local deployment of the weapons themselves

Investigating GNSS multipath effects induced by co-located Radar Corner Reflectors

Abstract Radar Corner Reflectors (CR) are increasingly used as reference targets for land surface deformation measurements with the Interferometric Synthetic Aperture Radar (InSAR) technique. When co-located with ground-based Global Navigation Satellite Systems (GNSS) infrastructure, InSAR observations at CR can be used to integrate relative measurements of surface deformation into absolute reference frames defined by GNSS. However, CR are also a potential source of GNSS multipath effects and may therefore have a detrimental effect on the GNSS observations. In this study, we compare daily GNSS coordinate time series and 30-second signal-to-noise ratio (SNR) observations for periods before and after CR deployment at a GNSS site. We find that neither the site coordinates nor the SNR values are significantly affected by the CR deployment, with average changes being within 0.1 mm for site coordinates and within 1 % for SNR values. Furthermore, we generate empirical site models by spatially stacking GNSS observation residuals to visualise and compare the spatial pattern in the surroundings of GNSS sites. The resulting stacking maps indicate oscillating patterns at elevation angles above 60 degrees which can be attributed to the CR deployed at the analysed sites. The effect depends on the GNSS antenna used at a site with the magnitude of multipath patterns being around three times smaller for a high-quality choke ring antenna compared to a ground plane antenna without choke rings. In general, the CR-induced multipath is small compared to multipath effects at other GNSS sites located in a different environment (e. g. mounted on a building)

Combination of GNSS and InSAR measured at co-located geodetic monitoring sites

Global Navigation Satellite Systems (GNSS) can provide a temporally dense set of geodetic coordinate observations in three dimensions at a limited number of discrete measurement points on the ground. Compared to this, the Interferometric Synthetic Aperture Radar (InSAR) technique gives a spatially dense set of geodetic observations of ground surface movement in the viewing geometry of the satellite platform, but with a temporal sampling limited to the orbital revisit of the satellite. Using both of these methods together can leverage the advantages of each to derive more accurate, validated surface displacement estimates with both high temporal and spatial resolution. In this paper, we discuss the properties of both techniques with a view to combined usage for improving future national datums. We apply differential GNSS processing to data observed at a local geodetic network in the Sydney region as well as time series InSAR analysis of Radarsat-2 data. We compare and validate surface displacements resulting from the two techniques at 21 geodetic monitoring sites equipped with GNSS and radar corner reflectors (CRs). The resulting GNSS/InSAR displacement time series agree at the level of 5 to 10 mm. This case study shows that co-located GNSS/CR sites are well-suited to compare and combine GNSS and InSAR measurements. An investigation of potential multipath effects introduced by the CRs attached directly to GNSS monumentation found that daily site coordinates are affected at a level below 0.1 mm. The GNSS/CR sites may hence serve as a local tie for future incorporation of InSAR into national datums. This will allow frequent updates of national geodetic networks and corresponding datums by using the large-scale and spatially dense information on surface displacements resulting from InSAR analyses

Demo: A Low-Cost Fleet Monitoring System

Organizations use fleet monitoring systems for e.g., vehicle tracking, driver behavior analysis, and efficient fleet management. Current systems are designed for commercial use and are of high cost. We present a prototype of a low-cost fleet monitoring system that could be used for non-commercial applications. The system is composed of a device, a service application, and a Web application. The device reads data such as speed and fuel from the internal network of the connected vehicle and the location of the vehicle and sends them to a remote service. The remote service processes and stores the data. The users use a Web application to view the data about their vehicles in real-time

RPR Review of Policy Research Preferences, Knowledge, and Citizen Probability Assessments of the Terrorism Risk of Nuclear Powerr opr_552 207..227

Abstract How does the American public assess risk when it comes to national security issues? This paper addresses this question by analyzing variation in citizen probabilit

A Climatology of Cold-Season Nonconvective Wind Events in the Great Lakes Region

A 44-yr climatology of nonconvective wind events (NCWEs) for the Great Lakes region has been created using hourly wind data for 38 first-order weather stations during the months of November through April. The data were analyzed in terms of the two National Weather Service (NWS) criteria for a high-wind watch or warning: sustained winds of at least 18 m s-1for at least 1 h or a wind gust of at least 26 m s-1for any duration. The results indicate a pronounced southwest quadrant directional preference for nonconvective high winds in this region. Between 70% and 76% of all occurrences that satisfied the NWS criteria for NCWEs were associated with wind directions from 180° through 270°. Within the southwest quadrant, the west-southwest direction is preferred, with 14%-35% of all NCWEs coming from this particular compass heading. This directional preference is borne out in five out of six stations with high occurrences of cold-season NCWEs (Buffalo, New York; Dayton, Ohio; Lansing, Michigan; Moline, Illinois; Springfield, Illinois). Given the geographic spread of these stations, a nontopographic cause for the directional preference of cold-season NCWEs is indicated. The connection between NCWEs and low pressure systems found in this climatology and in case studies suggests that midlatitude cyclone dynamics may be a possible cause of the directional preference

A Climatology of Cold-Season Nonconvective Wind Events in the Great Lakes Region

ABSTRACT A 44-yr climatology of nonconvective wind events (NCWEs) for the Great Lakes region has been created using hourly wind data for 38 first-order weather stations during the months of November through April. The data were analyzed in terms of the two National Weather Service (NWS) criteria for a high-wind watch or warning: sustained winds of at least 18 m s Ϫ1 for at least 1 h or a wind gust of at least 26 m s Ϫ1 for any duration. The results indicate a pronounced southwest quadrant directional preference for nonconvective high winds in this region. Between 70% and 76% of all occurrences that satisfied the NWS criteria for NCWEs were associated with wind directions from 180°through 270°. Within the southwest quadrant, the west-southwest direction is preferred, with 14%-35% of all NCWEs coming from this particular compass heading. This directional preference is borne out in five out of six stations with high occurrences of cold-season NCWEs (Buffalo, New York; Dayton, Ohio; Lansing, Michigan; Moline, Illinois; Springfield, Illinois). Given the geographic spread of these stations, a nontopographic cause for the directional preference of cold-season NCWEs is indicated. The connection between NCWEs and low pressure systems found in this climatology and in case studies suggests that midlatitude cyclone dynamics may be a possible cause of the directional preference

Abundance Patterns in the Draco, Sextans and Ursa Minor Dwarf Spheroidal Galaxies

The Keck I telescope has been used to obtain HIRES spectra for red giants belonging to the Draco, Sextans and Ursa Minor dwarf spheroidal (dSph) galaxies. An analysis of these spectra is presented, along with abundance ratios for more than 20 elements. The resulting database of element abundances for 17 stars is the most extensive yet assembled for stars in dSph environments. Our main findings are summarized as follows: (1) There is unambiguous evidence for a large internal spread in metallicity in all three galaxies: our program stars span a range of [Fe/H] = 1.53, 1.40 and 0.73 dex in Draco, Sextans and Ursa Minor, respectively. (2) The abundance patterns among the dSph stars are remarkably uniform, suggesting that all three galaxies have similar nucleosynthetic histories. (3) A comparison of the measured abundance ratios for our sample of dSph stars with published values for Galactic halo and disk field stars suggests that the dSph galaxies have 0.02 < [alpha/Fe] < 0.13 dex, whereas the halo field star sample has [alpha/Fe] ~ 0.28 dex over the same range in metallicity. (4) The most metal-rich dSph stars in our sample have [Y/Fe] abundances which are significantly lower than those measured for halo field stars of similar metallicity, while the measured [Ba/Eu] ratios for the dSph stars suggest that the early chemical evolution of these galaxies was dominated by the r-process. Taken together, these results suggest that the Galactic halo is unlikely to have assembled, in its entirety, through the disruption of dwarf galaxies similar to the low-luminosity dSphs studied here. (ABRIDGED).Comment: 24 pages, 8 postscript figures (including 6 color figures). Accepted for publication in the Astrophysical Journa

Exoplanet imaging data challenge: benchmarking the various image processing methods for exoplanet detection

The Exoplanet Imaging Data Challenge is a community-wide effort meant to offer a platform for a fair and common comparison of image processing methods designed for exoplanet direct detection. For this purpose, it gathers on a dedicated repository (Zenodo), data from several high-contrast ground-based instruments worldwide in which we injected synthetic planetary signals. The data challenge is hosted on the CodaLab competition platform, where participants can upload their results. The specifications of the data challenge are published on our website https://exoplanet-imaging-challenge.github.io/. The first phase, launched on the 1st of September 2019 and closed on the 1st of October 2020, consisted in detecting point sources in two types of common data-set in the field of high-contrast imaging: data taken in pupil-tracking mode at one wavelength (subchallenge 1, also referred to as ADI) and multispectral data taken in pupil-tracking mode (subchallenge 2, also referred to as ADI+mSDI). In this paper, we describe the approach, organisational lessons-learnt and current limitations of the data challenge, as well as preliminary results of the participants’ submissions for this first phase. In the future, we plan to provide permanent access to the standard library of data sets and metrics, in order to guide the validation and support the publications of innovative image processing algorithms dedicated to high-contrast imaging of planetary systems