Peer-to-Peer Communication Across Network Address Translators

Network Address Translation (NAT) causes well-known difficulties for peer-to-peer (P2P) communication, since the peers involved may not be reachable at any globally valid IP address. Several NAT traversal techniques are known, but their documentation is slim, and data about their robustness or relative merits is slimmer. This paper documents and analyzes one of the simplest but most robust and practical NAT traversal techniques, commonly known as "hole punching." Hole punching is moderately well-understood for UDP communication, but we show how it can be reliably used to set up peer-to-peer TCP streams as well. After gathering data on the reliability of this technique on a wide variety of deployed NATs, we find that about 82% of the NATs tested support hole punching for UDP, and about 64% support hole punching for TCP streams. As NAT vendors become increasingly conscious of the needs of important P2P applications such as Voice over IP and online gaming protocols, support for hole punching is likely to increase in the future.Comment: 8 figures, 1 tabl

Export plan for Maurertown trailers to Vietnam

Because of the scant information available on the market and competition in Vietnam, I recommend that Maurertown Trailers does not immediately enter the Vietnamese market. Prior to exporting to Vietnam, it would be best if Maurertown exports to other countries that are more similar to the United States market, such as Canada and Western Europe. If the company does determine that it is in its best interest to export to Vietnam, it should begin by engaging with trade shows, where it can showcase its product (most preferably its dump trailer since this attracts a wide customer base in the US) and gain an understanding of the Vietnamese market while necessarily building relationships with potential consumers and the general public. Keeping in line with the company’s current market base, it is recommended that Maurertown sell to the country’s construction companies, with a potential of someday selling to the large farming network found throughout Vietnam. The way by which Maurertown sells its trailers to these companies can vary, from using a distributor to selling it directly. Greater information on this and much more is found in this export plan

Vulnerability-attention analysis for space-related activities

Techniques for representing and analyzing trouble spots in structures and processes are discussed. Identification of vulnerable areas usually depends more on particular and often detailed knowledge than on algorithmic or mathematical procedures. In some cases, machine inference can facilitate the identification. The analysis scheme proposed first establishes the geometry of the process, then marks areas that are conditionally vulnerable. This provides a basis for advice on the kinds of human attention or machine sensing and control that can make the risks tolerable

Quantum inequalities for the free Rarita-Schwinger fields in flat spacetime

Using the methods developed by Fewster and colleagues, we derive a quantum inequality for the free massive spin-${3\over 2}$ Rarita-Schwinger fields in the four dimensional Minkowski spacetime. Our quantum inequality bound for the Rarita-Schwinger fields is weaker, by a factor of 2, than that for the spin-${1\over 2}$ Dirac fields. This fact along with other quantum inequalities obtained by various other authors for the fields of integer spin (bosonic fields) using similar methods lead us to conjecture that, in the flat spacetime, separately for bosonic and fermionic fields, the quantum inequality bound gets weaker as the the number of degrees of freedom of the field increases. A plausible physical reason might be that the more the number of field degrees of freedom, the more freedom one has to create negative energy, therefore, the weaker the quantum inequality bound.Comment: Revtex, 11 pages, to appear in PR

A Rigorous Free-form Lens Model of Abell 2744 to Meet the Hubble Frontier Fields Challenge

Hubble Frontier Fields (HFF) imaging of the most powerful lensing clusters provides access to the most magnified distant galaxies. The challenge is to construct lens models capable of describing these complex massive, merging clusters so that individual lensed systems can be reliably identified and their intrinsic properties accurately derived. We apply the free-form lensing method (WSLAP+) to A2744, providing a model independent map of the cluster mass, magnification, and geometric distance estimates to multiply-lensed sources. We solve simultaneously for a smooth cluster component on a pixel grid, together with local deflections by the cluster member galaxies. Combining model prediction with photometric redshift measurements, we correct and complete several systems recently claimed, and identify 4 new systems - totalling 65 images of 21 systems spanning a redshift range of 1.4<z<9.8. The reconstructed mass shows small enhancements in the directions where significant amounts of hot plasma can be seen in X-ray. We compare photometric redshifts with "geometric redshifts", finding a high level of self-consistency. We find excellent agreement between predicted and observed fluxes - with a best-fit slope of 0.999+-0.013 and an RMS of ~0.25 mag, demonstrating that our magnification correction of the lensed background galaxies is very reliable. Intriguingly, few multiply-lensed galaxies are detected beyond z~7.0, despite the high magnification and the limiting redshift of z~11.5 permitted by the HFF filters. With the additional HFF clusters we can better examine the plausibility of any pronounced high-z deficit, with potentially important implications for the reionization epoch and the nature of dark matter.Comment: Accepted for publication in ApJ with newly identified lensed images in complete HFF dat

Patriot Games? Determinants of Responses to Chinese and Foreign Sponsors of the Beijing Olympics

The paper assesses the generalizability of Speed and Thompson’s (2000) model of the determinants of sponsorship response to an important and growing market for sponsorship (China). It extends the model by considering differences in effects for foreign and domestically owned sponsors and the role of patriotism. The findings confirm that personal liking for the sponsored event, status of the event, attitude to the sponsor, perceived sincerity of the sponsor and perceived fit between the sponsor and the event are significant factors underpinning positive responses. In contrast to Speed and Thompson (2000), ubiquity of the sponsor is not significant for China. Whether the sponsor is of domestic or foreign origin is identified as an important moderator of sponsorship effects but there is no consistent evidence that foreign sponsors suffer from relatively poorer outcomes in emerging markets compared to domestically owned rivals

Mapping to underpin management of tropical littoral rainforest

[Extract] The aim of the project was to produce fine-resolution mapping of the location of the critically endangered Littoral Rainforest & Coastal Vine Thickets of Eastern Australia ecological community (LRF) between Townsville and Cooktown and the threats to its persistence and condition from the impacts of sea-level rise, storm surge and extreme weather events. A pilot study conducted in the Mission Beach area (Metcalfe et al. 2014) developed a mapping approach which accounts for the identification and distribution of Littoral rainforest consistent with the Listing Advice. This project extended that approach across the distribution of the ecological community from Townville to Cooktown. This project used coastal LiDAR data (1 m grid, 0.15 m accuracy) to compile fine-scale terrain layers to derive inundation levels for an 80 cm sea-level rise and for eight storm surge Annual Recurrence Intervals (ARIs) between 20 and 10,000 years. Spatial layers of the location of LRF and inundation were overlaid to determine the probability and magnitude of risk to the ecological community from these effects and to prioritise management interventions. The following spatial layers were derived and are available at the CSIRO data portal: • LRF vegetation that ‘wholly-equates’ to the EPBC Listing Advice • ‘Potential’ LRF delineating areas consistent with broad characteristics of the community described in the EPBC Listing Advice • Inundation statistics for each patch of wholly-equate LRF and potential LRF (patches defined by RE mapping) indicating: o the proportion of each patch inundated with 80 cm sea-level rise o the proportion of each patch inundated at each of 8 ARIs with and without sea-level rise o the ARI at which a patch first becomes inundated o the ARI at which a patch is >20% inundated o the ARI at which a patch is >50% inundated We describe the distribution and extent of LRF in the study region, the current pressures on LRF in the region and the distribution of LRF in the region with respect to the conservation estate and other tenures. Our mapping and inundation analysis can be used to define a number of different roles of LRF in the landscape on which a portfolio of management approaches can be derived which allow for the short-, medium- and long-term effects of sea-level rise and storm surge. We define ‘refugial’, ‘buffer’ and ‘leading-edge’ LRF patches by the relative frequency at which they become inundated and suggest management actions to improve resilience of the community as a whole

A Free-Form Prediction for the Reappearance of Supernova Refsdal in the Hubble Frontier Fields Cluster MACSJ1149.5+2223

The massive cluster MACSJ1149.5+2223(z=0.544) displays five very large lensed images of a well resolved spiral galaxy at $z_{\rm spect}=1.491$. It is within one of these images that the first example of a multiply-lensed supernova has been detected recently as part of the Grism Lens-Amplified Survey from Space. The depth of this data also reveals many HII regions within the lensed spiral galaxy which we identify between the five counter-images. Here we expand the capability of our free-form method to incorporate these HII regions locally, with other reliable lensed galaxies added for a global solution. This improved accuracy allows us to estimate when the Refsdal supernova will appear within the other lensed images of the spiral galaxy to an accuracy of $\sim$ 7\%. We predict this supernova will reappear in one of the counter-images (RA=11:49:36.025, DEC=+22:23:48.11, J2000) and on November 1$^{st}$ 2015 (with an estimated error of $\pm$ 25 days) it will be at the same phase as it was when it was originally discovered, offering a unique opportunity to study the early phases of this supernova and to examine the consistency of the mass model and the cosmological model that have an impact on the time delay prediction.Comment: 12 images, 11 pages. Mateches accepted version in MNRAS. MNRAS in pres