The system parameters of the polars MR Ser and ST LMi

We obtain the NaI 8183,8195 absorption line radial velocity curves for the polars ST LMi and MR Ser, from which we find the semi-amplitudes to be K_abs=329=+/-6 kms-1 and K_abs=289+/-9 kms-1 respectively. We find that for both systems the effects on the \NaI absorption lines due to X-rays heating the inner face of the secondary are negligible, and so the values obtained for K_abs can be taken as the true semi-amplitude of the secondary star. We then determine the projected rotational velocities, vsini, to be 104+/-9 kms-1 and 66+/-13 kms-1 for ST LMi and MR Ser respectively which enables their mass ratios to be calculated. For ST LMi and MR Ser we find the mass ratio to be 0.22+/-0.04 and 0.10+/-0.05 respectively; values which are significantly different only at the 94 percent level. We show that ``spike'' in the orbital period distribution of polars is a significant feature, although the discovery of only one more system with a period outside the ``spike'' would decrease its significance below a 99 percent confidence level. We conclude that, even if the limb darkening coefficients for the secondary stars in ST LMi and MR Ser are the same, we cannot rule out the two systems having identical parameters. Therefore our observations are compatible with the theory explaining the ``spike'' in the period distribution of the AM Hers.Comment: 6 pages, accepted for MNRAS, use mn.sty, 9 postscript figures, 3 table

Evaluation of SRM flex bearing materials and processes

Tensile, peel, and shear testing was performed on combinations of primers, adhesives, tycements and rubber compounds cured at various times and temperatures. The materials used in the fabrication of the solid rocket motor flex bearing as well as in other systems were evaluated. A compatibility study between adhesives and tycements was initiated. The flex bearing mold design was reviewed by our tooling experts

The AGB stars of the intermediate-age LMC cluster NGC 1846 Variability and age determination

Aims: To investigate variability and to model the pulsational behaviour of AGB variables in the intermediate-age LMC cluster NGC 1846. Methods: Our own photometric monitoring has been combined with data from the MACHO archive to detect 22 variables among the cluster's AGB stars and to derive pulsation periods. According to the global parameters of the cluster we construct pulsation models taking into account the effect of the C/O ratio on the atmospheric structure. In particular, we have used opacities appropriate for both O-rich stars and carbon stars in the pulsation calculations. Results: The observed P-L-diagram of NGC 1846 can be fitted using a mass of the AGB stars of about 1.8 M_{\sun}. We show that the period of pulsation is increased when an AGB star turns into a carbon star. Using the mass on the AGB defined by the pulsational behaviour of our sample we derive a cluster age of $1.4\times10^{9}$ years. This is the first time the age of a cluster has been derived from the variability of its AGB stars. The carbon stars are shown to be a mixture of fundamental and first overtone radial pulsators.Comment: accepted for publication in Astronomy and Astrophysic

A novel method for subjective picture quality assessment and further studies of HDTV formats

This is the author's accepted manuscript. The final published article is available from the link below. Copyright @ IEEE 2008.This paper proposes a novel method for the assessment of picture quality, called triple stimulus continuous evaluation scale (TSCES), to allow the direct comparison of different HDTV formats. The method uses an upper picture quality anchor and a lower picture quality anchor with defined impairments. The HDTV format under test is evaluated in a subjective comparison with the upper and lower anchors. The method utilizes three displays in a particular vertical arrangement. In an initial series of tests with the novel method, the HDTV formats 1080p/50,1080i/25, and 720p/50 were compared at various bit-rates and with seven different content types on three identical 1920 times 1080 pixel displays. It was found that the new method provided stable and consistent results. The method was tested with 1080p/50,1080i/25, and 720p/50 HDTV images that had been coded with H.264/AVC High profile. The result of the assessment was that the progressive HDTV formats found higher appreciation by the assessors than the interlaced HDTV format. A system chain proposal is given for future media production and delivery to take advantage of this outcome. Recommendations for future research conclude the paper

Human resource management in India: strategy, performance and complementarity

This study seeks to explore which types of HR practice are associated with better organisational performance (OP). Whilst the core finding—that specific HR practices lead to better organisational outcomes may not be surprising—we also found an absence of complementarity. Normally, the absence of complementarities would suggest limitations in institutional supports; on the one hand, however, institutional shortfalls are not unique to India and may be encountered in many emerging market settings. In contrast, the great internal diversity of the Indian setting, with strong variations recognised amongst institutions, along with enforcement capabilities, might suggest that these tendencies are particularly pronounced. We also found a strong link between the intrinsic rewards and performance—an unexpected result in a low-income country, where wages are generally low. We suggest that this may reflect the nature of the labour market and the limited (and possibly proportionately shrinking) pool of good jobs, making exit a difficult option for all but the best qualified. Whilst this puts employees in a poor bargaining position in bidding-up pay (making pay rises seem unfeasible), the intrinsic attributes of the job become more important

Hands on - hands off: on hitting your thumb with a virtual hammer

In a wired world even the most physically embodied craft skills are affected by computer facilitated communication. To consider how different sorts of space – both real and virtual – influence the learning of craft skills this paper presents three types of space – the ‘real’ space of a jewellery workshop, an online ‘wiki’ space for learning how to make a folding knife mediated by face to face interaction and an online discussion group about French Horn making. Some features common to the learning of any craft skill are discussed as well as some current ideas about the influence of networked communication on the way people relate to each other. Conclusions are drawn about the relationships between different types of learner, different types of skill and different types of learning space which demonstrate that while there may be no substitute for face to face contact in learning the most embodied craft skills, even in real-world settings a significant proportion of learning depends on social interaction which may be reproduced online. Keywords: Craft learning; Apprenticeship; Communities of Practice; Online Networks</p

Estimation of fractal dimension for a class of Non-Gaussian stationary processes and fields

We present the asymptotic distribution theory for a class of increment-based estimators of the fractal dimension of a random field of the form g{X(t)}, where g:R\to R is an unknown smooth function and X(t) is a real-valued stationary Gaussian field on R^d, d=1 or 2, whose covariance function obeys a power law at the origin. The relevant theoretical framework here is ``fixed domain'' (or ``infill'') asymptotics. Surprisingly, the limit theory in this non-Gaussian case is somewhat richer than in the Gaussian case (the latter is recovered when g is affine), in part because estimators of the type considered may have an asymptotic variance which is random in the limit. Broadly, when g is smooth and nonaffine, three types of limit distributions can arise, types (i), (ii) and (iii), say. Each type can be represented as a random integral. More specifically, type (i) can be represented as the integral of a certain random function with respect to Lebesgue measure; type (ii) can be represented as the integral of a second random functio

A data-based power transformation for compositional data

Compositional data analysis is carried out either by neglecting the compositional constraint and applying standard multivariate data analysis, or by transforming the data using the logs of the ratios of the components. In this work we examine a more general transformation which includes both approaches as special cases. It is a power transformation and involves a single parameter, {\alpha}. The transformation has two equivalent versions. The first is the stay-in-the-simplex version, which is the power transformation as defined by Aitchison in 1986. The second version, which is a linear transformation of the power transformation, is a Box-Cox type transformation. We discuss a parametric way of estimating the value of {\alpha}, which is maximization of its profile likelihood (assuming multivariate normality of the transformed data) and the equivalence between the two versions is exhibited. Other ways include maximization of the correct classification probability in discriminant analysis and maximization of the pseudo R-squared (as defined by Aitchison in 1986) in linear regression. We examine the relationship between the {\alpha}-transformation, the raw data approach and the isometric log-ratio transformation. Furthermore, we also define a suitable family of metrics corresponding to the family of {\alpha}-transformation and consider the corresponding family of Frechet means.Comment: Published in the proceddings of the 4th international workshop on Compositional Data Analysis. http://congress.cimne.com/codawork11/frontal/default.as