Performance modelling of the Cambridge Fast Ring protocol

The Cambridge Fast Ring is high-speed slotted ring. The features that make it suitable for use at very large transmission rates are the synchronous transmission, the simplicity of the medium-access-control protocol, and the possibility of immediate retransmission of erroneous packets. A novel analytical model of the Cambridge Fast Ring with normal slots is presented. The model is shown to be accurate and usable over wide range of parameters. A performance analysis based on this model is presented

Cremation practices and the creation of monument complexes: the Neolithic cremation cemetery at Forteviot, Strathearn, Perth & Kinross, Scotland, and its comparanda

Around the beginning of the 3rd millennium cal bc a cremation cemetery was established at Forteviot, central Scotland. This place went on to become one of the largest monument complexes identified in Mainland Scotland, with the construction of a palisaded enclosure, timber structures, and a series of henge monuments and other enclosures. The cemetery was established between 3080 and 2900 cal bc, probably in the 30th century cal bc, which is contemporary with the cremation cemetery at Stonehenge. Nine discrete deposits of cremated bone, representing the remains of at least 18 people, were identified. In most instances they were placed within cut features and, in one case, a series of cremation deposits was associated with a broken standing stone. This paper includes the first detailed assessment of the cremated remains at Forteviot and the features associated with the cemetery, and explores how the establishment of this cemetery may have been both a catalyst and inspiration for the elaborate monument building and prolonged acts of remembrance that occurred at this location over a period of almost 1000 years. The paper also outlines the parallels for Forteviot across Britain and, for the first time, draws together the dating evidence (including Bayesian modelling) for this major category of evidence for considering the nature of late 4th/early 3rd millennium cal bc society. The results and discussion have wide implications and resonances for contemplating the establishment and evolution of monument complexes in prehistoric Britain and beyond

Optimal edge termination for high oxide reliability aiming 10kV SiC n-IGBTs

The edge termination design strongly affects the ability of a power device to support the desired voltage and its reliable operation. In this paper we present three appropriate termination designs for 10kV n-IGBTs which achieve the desired blocking requirement without the need for deep and expensive implantations. Thus, they improve the ability to fabricate, minimise the cost and reduce the lattice damage due to the high implantation energy. The edge terminations presented are optimised both for achieving the widest immunity to dopant activation and to minimise the electric field at the oxide. Thus, they ensure the long-term reliability of the device. This work has shown that the optimum design for blocking voltage and widest dose window does not necessarily give the best design for reliability. Further, it has been shown that Hybrid Junction Termination Extension structure with Space Modulated Floating Field Rings can give the best result of very high termination efficiency, as high as 99%, the widest doping variation immunity and the lowest electric field in the oxide

The Morphology of the Expanding Ejecta of V2491 Cygni (2008 N.2)

Determining the evolution of the ejecta morphology of novae provides valuable information on the shaping mechanisms in operation at early stages of the nova outburst. Understanding such mechanisms has implications for studies of shaping for example in proto-Planetary Nebulae. Here we perform morpho-kinematical studies of V2491 Cyg using spectral data to determine the likely structure of the ejecta and its relationship to the central system and shaping mechanisms. We use Shape to model different morphologies and retrieve their spectra. These synthetic spectra are compared with observed spectra to determine the most likely morphology giving rise to them, including system inclination and expansion velocity of the nova ejecta. We find the best fit remnant morphology to be that of polar blobs and an equatorial ring with an implied inclination of 80$^{+3}_{-12}$ degrees and an maximum expansion velocity of the polar blobs of 3100$^{+200}_{-100}$ km/s and for the equatorial ring 2700$^{+200}_{-100}$ km/s. This inclination would suggest that we should observe eclipses which will enable us to determine more precisely important parameters of the central binary. We also note that the amplitude of the outburst is more akin to the found in recurrent nova systems.Comment: 9 pages, 7 figures, accepted for publication in MNRA

Kinematics in the Central Kiloparsec of Spiral Galaxies

Results from kinematic observations of the central regions of spiral galaxies are reviewed, with particular emphasis on starburst and AGN hosts. While morphological studies lead to important insight, a more complete understanding of the physical processes that drive the evolution of the central regions can be achieved with measurements of the kinematics of gas and stars. Here, a variety of observational techniques at different wavelengths is critically discussed, and specific areas of interest are highlighted, such as inflow in barred galaxies and the origin of nuclear spiral arms. A brief discussion of a number of case studies is presented to illustrate recent progress.Comment: Invited review, to appear in The Central kpc of Starbursts and AGN: the La Palma Connection, eds. J. H. Knapen, J. E. Beckman, I. Shlosman, and T. J. Mahoney (ASP: San Francisco), Vol. 249. 18 pages latex, includes 9 postscript figures. Uses newpasp.sty (included

SHARP - I. A high-resolution multi-band view of the infra-red Einstein ring of JVAS B1938+666

We present new mass models for the gravitational lens system B1938+666, using multi-wavelength data acquired from Keck adaptive optics (AO) and Hubble Space Telescope (HST) observations. These models are the first results from the Strong-lensing at High Angular Resolution Program (SHARP), a project designed to study known quadruple-image and Einstein ring lenses using high-resolution imaging, in order to probe their mass distributions in unprecedented detail. Here, we specifically highlight differences between AO- and HST-derived lens models, finding that -- at least when the lens and source galaxies are both bright and red, and the system has a high degree of circular symmetry -- AO-derived models place significantly tighter constraints on model parameters. Using this improved precision, we infer important physical properties about the B1938+666 system, including the mass density slope of the lensing galaxy (gamma = 2.045), the projected dark matter mass fraction within the Einstein radius (M_dark/M_lens = 0.55), and the total magnification factor of the source galaxy (~ 13). Additionally, we measure an upper-limit constraint on luminous substructure (M_V > 16.2), based on the non-detection of bright satellite galaxies in all data sets. Finally, we utilize the improved image resolution of the AO data to reveal the presence of faint arcs outside of the primary Einstein ring. The positions and orientations of these arcs raise the intriguing possibility that B1938+666 has a second source galaxy, located at a more distant redshift. However, future work is needed to verify this hypothesis.Comment: 12 pages, 7 figures; Accepted for publication in MNRA

An improved digital watermarking algorithm using combination of least significant bit (LSB) and inverse bit

Software watermarking is one of the most important methods for protecting copyrights and authenticating ownership; which can be used to prevent software piracy. In order to provide high quality watermarked image, the watermarked image should be imperceptible. Least significant bit (LSB) is a technique that has been used for digital watermarking. Many researchers have improved LSB to embed watermark in the image. In this thesis, we introduce an improved digital watermarking algorithm using least significant bit (LSB). This method is chosen due to its minimal effect on the image. LSB is used by inversing the binary values of the watermark text and shifting the watermark according to the odd or even number of pixel coordinates of image before embedding the watermark. The proposed algorithm can be personalized according to the length of the watermark text. If the length of the watermark text is more than ((M*N)/8)-2 (where M*N is the amount of pixels in the image), the proposed algorithm will also embed the extra of the watermark text in the second LSB. We compare our proposed algorithm with the 1-LSB algorithm and Lee’s algorithm and Yang's algorithm using Peak signal�to-noise ratio (PSNR). The value of the watermarked dock image is 54.5691 dB which is higher than the traditional LSB 53.6950 dB and Lee's algorithm 53.7041 db and Yang's algorithm 52.4518 dB. Also in the other image, the proposed algorithm got the highest value of PSNR. This improved algorithm improved its quality of the watermarked image. We also attack the watermarked image by using cropping and adding noise and we got good results as wel