251 research outputs found
Can Punctured Rate-1/2 Turbo Codes Achieve a Lower Error Floor than their Rate-1/3 Parent Codes?
In this paper we concentrate on rate-1/3 systematic parallel concatenated
convolutional codes and their rate-1/2 punctured child codes. Assuming
maximum-likelihood decoding over an additive white Gaussian channel, we
demonstrate that a rate-1/2 non-systematic child code can exhibit a lower error
floor than that of its rate-1/3 parent code, if a particular condition is met.
However, assuming iterative decoding, convergence of the non-systematic code
towards low bit-error rates is problematic. To alleviate this problem, we
propose rate-1/2 partially-systematic codes that can still achieve a lower
error floor than that of their rate-1/3 parent codes. Results obtained from
extrinsic information transfer charts and simulations support our conclusion.Comment: 5 pages, 7 figures, Proceedings of the 2006 IEEE Information Theory
Workshop, Chengdu, China, October 22-26, 200
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Profit-oriented cooperative caching algorithm for hierarchical content centric networking
Separation of natural from laboratory-grown diamond using time-gated luminescence imaging
A technique that expands on the surface luminescence imaging used in the DiamondView instrument has been developed at De Beers Group Technology, Maidenhead, UK. This provides an additional level of imaging information by way of separating prompt and delayed surface luminescence. The technique has the added benefit of quickly and easily distinguishing colorless or near-colorless natural diamond from laboratory-grown diamond. It can be applied when the identification of natural diamond is required in the study of single stones, multiples in batches, set jewelry, or in a fully automated process. The prompt and delayed luminescence characteristics of natural diamond are compared with a range of chemical vapor deposition (CVD) and high-pressure, high-temperature (HPHT) synthetic diamonds. Of significant interest are some of the less common CVD synthetic samples that have been observed in recent years. This article will summarize the luminescence observed in different diamond types, discuss its spectral characteristics, and serve as a useful reference when interpreting such luminescence images
Wage Distribution Impacts of Higher Education Faculty Unionization
The literature on the effects of unions on the distribution of wages at the macroeconomic and inter-industry levels has given little attention to the effects at the firm level. At the same time, research on collective bargaining impacts in higher education has focused on the overall wage level rather than on the distribution of salaries. Using panel data on individual faculty members, we find faculty unionization to be associated with a significant flattening of the wage distribution across academic disciplines. This has implications for why faculty might choose to unionize, even in the absence of an overall wage premium
Veterinary dairy herd fertility service provision in seasonal and non-seasonal dairy industries - a comparison
The decline in dairy herd fertility internationally has highlighted the limited impact of traditional veterinary approaches to bovine fertility management. Three questionnaire surveys were conducted at buiatrics conferences attended by veterinary practitioners on veterinary dairy herd fertility services (HFS) in countries with a seasonal (Ireland, 47 respondents) and non-seasonal breeding model (The Netherlands, 44 respondents and Portugal, 31 respondents). Of the 122 respondents, 73 (60%) provided a HFS and 49 (40%) did not. The majority (76%) of all practitioners who responded stated that bovine fertility had declined in their practice clients' herds with inadequate cow management, inadequate nutrition and increased milk yield as the most important putative causes. The type of clients who adopted a herd fertility service were deemed more educated than average (70% of respondents), and/or had fertility problems (58%) and/or large herds (53%). The main components of this service were routine postpartum examinations (95% of respondents), fertility records analysis (75%) and ultrasound pregnancy examinations (69%). The number of planned visits per annum varied between an average of four in Ireland, where breeding is seasonal, and 23 in Portugal, where breeding is year-round. The benefits to both the practitioner and their clients from running a HFS were cited as better fertility, financial rewards and job satisfaction. For practitioners who did not run a HFS the main reasons given were no client demand (55%) and lack of fertility records (33%). Better economic evidence to convince clients of the cost-benefit of such a service was seen as a major constraint to adoption of this service by 67% of practitioners
Milli-arcsecond images of the Herbig Ae star HD 163296
The very close environments of young stars are the hosts of fundamental
physical processes, such as planet formation, star-disk interactions, mass
accretion, and ejection. The complex morphological structure of these
environments has been confirmed by the now quite rich data sets obtained for a
few objects by near-infrared long-baseline interferometry. We gathered numerous
interferometric measurements for the young star HD163296 with various
interferometers (VLTI, IOTA, KeckI and CHARA), allowing for the first time an
image independent of any a priori model to be reconstructed. Using the
Multi-aperture image Reconstruction Algorithm (MiRA), we reconstruct images of
HD 163296 in the H and K bands. We compare these images with reconstructed
images obtained from simulated data using a physical model of the environment
of HD 163296. We obtain model-independent and -band images of the
surroundings of HD 163296. The images present several significant features that
we can relate to an inclined asymmetric flared disk around HD 163296 with the
strongest intensity at about 4-5 mas. Because of the incomplete spatial
frequency coverage, we cannot state whether each of them individually is
peculiar in any way. For the first time, milli-arcsecond images of the
environment of a young star are produced. These images confirm that the
morphology of the close environment of young stars is more complex than the
simple models used in the literature so far.Comment: 11 pages, 10 figures, accepted A&A pape
Coffee consumption has no acute effects on glucose metabolism in healthy men : a randomized crossover clinical trial
We investigate the effect of coffee (caffeinated and decaffeinated) on glucose effectiveness and insulin sensitivity using the stable isotope minimal model protocol with oral glucose administration in healthy men
Multiabsorber Transition-Edge Sensors for X-Ray Astronomy
We are developing arrays of position-sensitive microcalorimeters for future x-ray astronomy applications. These position-sensitive devices commonly referred to as hydras consist of multiple x-ray absorbers, each with a different thermal coupling to a single-transition-edge sensor microcalorimeter. Their development is motivated by a desire to achieve very large pixel arrays with some modest compromise in performance. We report on the design, optimization, and first results from devices with small pitch pixels (<75 m) being developed for a high-angular and energy resolution imaging spectrometer for Lynx. The Lynx x-ray space telescope is a flagship mission concept under study for the National Academy of Science 2020 decadal survey. Broadband full-width-half-maximum (FWHM) resolution measurements on a 9-pixel hydra have demonstrated E(FWHM) = 2.23 0.14 eV at Al-K, E(FWHM) = 2.44 0.29 eV at Mn-K, and E(FWHM) = 3.39 0.23 eV at Cu-K. Position discrimination is demonstrated to energies below <1 keV and the device performance is well-described by a finite-element model. Results from a prototype 20-pixel hydra with absorbers on a 50-m pitch have shown E(FWHM) = 3.38 0.20 eV at Cr-K1. We are now optimizing designs specifically for Lynx and extending the number of absorbers up to 25/hydra. Numerical simulation suggests optimized designs could achieve 3 eV while being compatible with the bandwidth requirements of the state-of-the art multiplexed readout schemes, thus making a 100,000 pixel microcalorimeter instrument a realistic goal
Exploring patterns of recurrent melanoma in Northeast Scotland to inform the introduction a digital self-examination intervention
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Wage Distribution Impacts of Higher Education Faculty Unionization
The literature on the effects of unions on the distribution of wages at the macroeconomic and inter-industry levels has given little attention to the effects at the firm level. At the same time, research on collective bargaining impacts in higher education has focused on the overall wage level rather than on the distribution of salaries. Using panel data on individual faculty members, we find faculty unionization to be associated with a significant flattening of the wage distribution across academic disciplines. This has implications for why faculty might choose to unionize, even in the absence of an overall wage premium
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