Spiral Growth Manufacturing (SGM) – A Continuous Additive Manufacturing Technology for Processing Metal Powder by Selective Laser Melting

Spiral growth manufacturing is a new innovative powder based rapid manufacturing technique. The innovation exists in the methodology in which powder layers are deposited. Unlike other pre-placed powder systems, the deposited layers move relative to the location at which they are processed. This is made possible by a rotating build drum into which powder is deposited, in spiralled layers, from a stationary hopper. With this configuration powder can be continuously deposited and levelled and simultaneously processed, eliminating delays in the build cycle. Stainless steel and cobalt-chrome powder is selectively melted using a 100W flash lamp pumped Nd:YAG laser. This paper reports on factors affecting build rate and on build strategies for creating a number of axis-symmetric thin and thick walled cylinders. Experimental results suggest that build rate for thin walled structures bonded to a substrate will ultimately be governed by tangential movements of the powder particles when frictional forces are not sufficient to accelerate the particles along a curved path, provided that enough laser power is available for melting. Even melt pool balling, which is evident when melting one layer at high speeds, diminishes in multiple layer builds due to re-melting and infilling.Mechanical Engineerin

Using a task-based approach in evaluating the usability of BoBIs in an e-book environment

This paper reports on a usability evaluation of BoBIs (Back-of-the-book Indexes) as searching and browsing tools in an e-book environment. This study employed a task-based approach and within-subject design. The retrieval performance of a BoBI was compared with a ToC and Full-Text Search tool in terms of their respective effectiveness and efficiency for finding information in e-books. The results demonstrated that a BoBI was significantly more efficient (faster) and useful compared to a ToC or Full-Text Search tool for finding information in an e-book environment

The Cosmic Coincidence as a Temporal Selection Effect Produced by the Age Distribution of Terrestrial Planets in the Universe

The energy densities of matter and the vacuum are currently observed to be of the same order of magnitude: $(\Omega_{m 0} \approx 0.3) \sim (\Omega_{\Lambda 0} \approx 0.7)$. The cosmological window of time during which this occurs is relatively narrow. Thus, we are presented with the cosmological coincidence problem: Why, just now, do these energy densities happen to be of the same order? Here we show that this apparent coincidence can be explained as a temporal selection effect produced by the age distribution of terrestrial planets in the Universe. We find a large ($\sim 68$) probability that observations made from terrestrial planets will result in finding $\Omega_m$ at least as close to $\Omega_{\Lambda}$ as we observe today. Hence, we, and any observers in the Universe who have evolved on terrestrial planets, should not be surprised to find $\Omega_m \sim \Omega_{\Lambda}$. This result is relatively robust if the time it takes an observer to evolve on a terrestrial planet is less than $\sim 10$ Gyr.Comment: Submitted to Ap

The Arecibo Methanol Maser Galactic Plane Survey - II: Statistical and Multi-wavelength Counterpart Analysis

We present an analysis of the properties of the 6.7 GHz methanol maser sample detected in the Arecibo Methanol Maser Galactic Plane Survey. The distribution of the masers in the Galaxy, and statistics of their multi-wavelength counterparts is consistent with the hypothesis of 6.7 GHz maser emission being associated with massive young stellar objects. Using the detection statistics of our survey, we estimate the minimum number of methanol masers in the Galaxy to be 1275. The l-v diagram of the sample shows the tangent point of the Carina-Sagittarius spiral arm to be around 49.6 degrees, and suggests occurrence of massive star formation along the extension of the Crux-Scutum arm. A Gaussian component analysis of the maser spectra shows the mean line-width to be 0.38 km/s which is more than a factor of two larger than what has been reported in the literature. We also find no evidence that faint methanol masers have different properties than those of their bright counterparts.Comment: Accepted by ApJ; Revised footnote number 3 on page 8 based on private communicatio

The management of type 1 and type 2 diabetes in pregnancy

Pregestational diabetes is a common medical complication of pregnancy and preconception planning is an essential component of care for affected women of childbearing age. Once pregnant, structured care in a multidisciplinary team setting is necessary to ensure optimal outcomes. Although significant progress has been made, these women and their offspring remain to have a significantly elevated risk of multiple adverse complications. Structured programmes using information technology and enabling access to novel technologies may facilitate our goal of ensuring an outcome closer to that of a pregnancy unaffected by diabetes

Stochastic series expansion method for quantum Ising models with arbitrary interactions

A quantum Monte Carlo algorithm for the transverse Ising model with arbitrary short- or long-range interactions is presented. The algorithm is based on sampling the diagonal matrix elements of the power series expansion of the density matrix (stochastic series expansion), and avoids the interaction summations necessary in conventional methods. In the case of long-range interactions, the scaling of the computation time with the system size N is therefore reduced from N^2 to Nln(N). The method is tested on a one-dimensional ferromagnet in a transverse field, with interactions decaying as 1/r^2.Comment: 9 pages, 5 figure

Confirmation of the Luminous Blue Variable nature of AFGL 2298

We present new photometric and spectroscopic observations of the stellar source AFGL 2298 (= IRAS 18576+0341) that has recently been proposed as a candidate Luminous Blue Variable (LBV). Our data confirm that the star is a highly luminous B supergiant which is both spectroscopically and photometrically variable. Assuming a distance of 10 kpc, comparison of the 2001 June data to synthetic spectra suggest stellar parameters of T=12.5 kK, log(L/L⊙)=6.2 and Ṁ=5xE-5 M⊙ yr-1. Data obtained in 2002 August indicate an increase in both temperature (=15 kK) and mass loss rate (=1.2xE-4 M⊙ yr-1) at constant bolometric luminosity. These physical parameters place AFGL 2298 at the Humphreys-Davidson limit for the most luminous stars known. We conclude that the position of AFG 2298 in the HR diagram, the significant variability observed between 1999-2002 and presence of a massive ejection nebula are consistent with a classification of AFGL 2298 as a bona fide LBV