Cramér-Rao Bound for Hybrid GNSS-Terrestrial Cooperative Positioning

In this contribution we derive an expression of the Cramer-Rao bound for hybrid cooperative positioning, where GNSS information is combined with terrestrial range measurements through exchange of peer-to-peer messages. These results provide a theoretical characterization of achievable performance of hybrid positioning schemes, as well as allow to identify critical network configurations and devise optimized node placement strategies

Cramér-Rao, Bound for Hybrid Peer-to-Peer Positioning

Presented at IEEE Communication Theory Workshop (CTW), Cancun, Mexico, May 10-12, 2010. PROCEEDINGS ARE NOT AVAILABL

Drag force in a string model dual to large-N QCD

We compute the drag force exerted on a quark and a di-quark systems in a background dual to large-N QCD at finite temperature. We find that appears a drag force in the former setup with flow of energy proportional to the mass of the quark while in the latter there is no dragging as in other studies. We also review the screening length.Comment: 15 pages, typos removed, error corrected, refs adde

Capacity building in Ocean Bathymetry: The Nippon Foundation GEBCO Training Programme at the University of New Hampshire

A successful Capacity Building project in hydrography is underway at the University of New Hampshire. Organised by the General Bathymetric Chart of the Oceans and sponsored by the Nippon Foundation, the programme trains hydrographers and other marine scientists in bathymetric mapping. Participants are formally prepared to produce bathymetric maps when they return to their home countries through a combination of graduate level courses and workshops, practical field training, participation in deep ocean research cruises, working visits to other laboratories and institutions, focused lectures from visiting experts, and the preparation of a bathymetry map of their area from public domain data. Intangible but necessary preparation includes the networking with professionals in bathymetry and related fields within Ocean Mapping, and the building of a cadre of graduates who will form the basis of international bathymetric mapping in the future

Anelastic Phenomena in Mg-Al Alloys

Cyclic loading-unloading in tension and compression has been used to quantify the anelastic behaviour, in the form of hysteresis loops, of pure Mg and three Mg-Al alloys (0.5, 2, and 9 at.% Al). The effect reached a maximum at a plastic strain of approximate to 0.02 for all of the materials, and decreased at higher strains. The amount of anelasticity at any given strain was smaller for the dilute alloys in comparison with the pure Mg whereas it increased above that of pure Mg for the most concentrated alloy. Possible reasons for this behaviour are discussed in terms of reversible twinning, solid solution softening, and hardening and short range order

Effect of composition on secondary dendrite arm spacing of Al-Si-Cu-Mg (Fe/Mn) alloys for a given cooling rate

Experiments were carried out to study the variation of secondary dendrite arm spacing (SDAS) of Al-Si-Cu-Mg-(Fe/Mn) alloys with the cooling rate and composition. Sand casting trials were carried out in Al-Si-Cu-Mg-(Fe/Mn) alloys with varying compositions of Si, Cu and Fe using an inverted mould. Alloys were prepared in an induction furnace at about 730ºC and triple-plate castings were cast using chills at the bottom of the plates for promoting directional solidification. Thermal information was acquired using pre-installed thermocouples through the mould wall. Optical microscopy studies were implemented to study the variation of secondary dendrite arm spacing (SDAS) as a function of chemical composition and cooling rate. The relationships between cooling rate and SDAS were plotted for the alloys and SDAS decreased with an increase in cooling rate and also with the increase in alloy composition

The inner environment of Z~CMa: High-Contrast Imaging Polarimetry with NaCo

Context. Z\,CMa is a binary composed of an embedded Herbig Be and an FU Ori class star separated by $\sim100$ au. Observational evidence indicate a complex environment in which each star has a circumstellar disk and drives a jet, and the whole system is embedded in a large dusty envelope. Aims. We aim to probe the circumbinary environment of Z\,CMa in the inner 400 au in scattered light. Methods. We use high contrast imaging polarimetry with VLT/NaCo at $H$ and $K_s$ bands. Results. The central binary is resolved in both bands. The polarized images show three bright and complex structures: a common dust envelope, a sharp extended feature previously reported in direct light, and an intriguing bright clump located 0\farcs3 south of the binary, which appears spatially connected to the sharp extended feature. Conclusions.We detect orbital motion when compared to previous observations, and report a new outburst driven by the Herbig star. Our observations reveal the complex inner environment of Z\,CMa with unprecedented detail and contrast.Comment: Accepted for publication in A&A Letter

An Upper Limit on the Mass of the Circumplanetary Disk for DH Tau b

Indexación: Scopus.DH Tau is a young (sim;1 Myr) classical T Tauri star. It is one of the few young PMS stars known to be associated with a planetary mass companion, DH Tau b, orbiting at large separation and detected by direct imaging. DH Tau b is thought to be accreting based on copious Ha emission and exhibits variable Paschen Beta emission. NOEMA observations at 230 GHz allow us to place constraints on the disk dust mass for both DH Tau b and the primary in a regime where the disks will appear optically thin. We estimate a disk dust mass for the primary, DH Tau A of 17.2 ± 1.7 MÅ, which gives a disk to star mass ratio of 0.014 (assuming the usual gas to dust mass ratio of 100 in the disk). We find a conservative disk dust mass upper limit of 0.42M⊕ for DH Tau b, assuming that the disk temperature is dominated by irradiation from DH Tau b itself. Given the environment of the circumplanetary disk, variable illumination from the primary or the equilibrium temperature of the surrounding cloud would lead to even lower disk mass estimates. A MCFOST radiative transfer model, including heating of the circumplanetary disk by DH Tau b and DH Tau A, suggests that a mass-averaged disk temperature of 22 K is more realistic, resulting in a dust disk mass upper limit of 0.09M⊕ for DH Tau b. We place DH Tau b in context with similar objects and discuss the consequences for planet formation models.http://iopscience.iop.org/article/10.3847/1538-3881/aa74cd/met