Bearing damage characteristics of fibre-reinforced countersunk composite bolted joints subjected to quasi-static shear loading

This paper studies the progression of damage in carbon fibre-reinforced polymer (CFRP) countersunk composite bolted joints (CBJs) with neat-fit clearance, subjected to quasi-static loading. Damage mechanisms, comprising of fibre buckling and breakage, matrix damage, shear damage and inter-laminar delamination within the CFRP composite parts of the joints have been studied. Load-displacement curves, X-ray and optical microscopic images in single- and three-bolt CBJs were used to investigate damage and deformation characteristics. The observations were then employed to further investigate the type of failure and the extent of damage. The evolution of damage within the composite parts was correlated to the failure characteristics of the joints: It was found that the type and extension of damage is strongly correlated with the ultimate failure load point of the joint in single-bolt CBJs. A combined inter/intra-laminar damage consisting of fibre cluster breakage, extensive fibre buckling, debonding and delamination was observed at the ultimate failure load. This study was then extended to three-bolt CBJ where damage surrounding each bolt and its corresponding failure load was strongly correlated: The final study showed that the ultimate failure point in single-bolt CBJ and the first-bolt-failure point in three-bolt CBJ correspond to the composite plies undergoing intra-laminar damage with the size reaching to the edge of the countersunk head. This damage developed extensively through the thickness of the composite parts underneath the countersink, and in the direction opposite to the loading direction. Outside the countersunk head, debonding and delamination were found to be the dominant damage driving mechanisms. Finally, a new design rule has been proposed to predict the response of multi-bolt joints (damage area and failure load) by using the response in single-bolt CBJ as an initial baseline

The Extended Methanol Maser Emission in W51

The European VLBI Network (EVN) has been used to make phase referenced, wide-field (several arcminute) spectral line observations of the 6.7-GHz methanol maser emission towards W51. In the W51main region, the bulk of the methanol is offset from an UCHII region. This probably indicates the methanol emission arises at the interface of the expanding UCHII region and not from an edge-on circumstellar disc, as previously suggested. Near the W51 IRS2 region, the methanol emission is associated with a very compact, extremely embedded source supporting the hypothesis that methanol masers trace the earliest stages of massive star formation. As well as these two previously well studied sites of star formation, many previously unknown regions star formation are detected, demonstrating that methanol masers are powerful means of detection young massive stars.Comment: 5 pages, 3 figure

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 development of absorptive capacity-based innovation in a construction SME

Traditionally, construction has been a transaction-oriented industry. However, it is changing from the design-bid-build process into a business based on innovation capability and performance management, in which contracts are awarded on the basis of factors such as knowledge, intellectual capital and skills. This change presents a challenge to construction-sector SMEs with scarce resources, which must find ways to innovate based on those attributes to ensure their future competitiveness. This paper explores how dynamic capability, using an absorptive capacity framework in response to these challenges, has been developed in a construction-based SME. The paper also contributes to the literature on absorptive capacity and innovation by showing how the construct can be operationalized within an organization. The company studied formed a Knowledge Transfer Partnership using action research over a two-year period with a local university. The aim was to increase its absorptive capacity and hence its ability to meet the changing market challenges. The findings show that absorptive capacity can be operationalized into a change management approach for improving capability-based competitiveness. Moreover, it is important for absorptive capacity constructs and language to be contextualized within a given organizational setting (as in the case of the construction-based SME in the present study)

A utilitarian antagonist: the zombie in popular video games

This article takes as its starting point the prevalence of the zombie in video games. I argue that, although the zombie games often superficially resemble filmic texts in their use of aesthetic and narrative, they must be understood, less as a set of conventions and thematic metaphors in the way that the zombie text has been read in film and television scholarship, and more as a utilisation of the zombie as a utilitarian antagonist that facilitates and permits the pleasures of violence and fantasy in video game play. Beginning with the Resident Evil and Left 4 Dead series of games I examine the way that games necessarily update the notion zombie as mass antagonist via the need to vary gameplay activity through different styles of adversary for players. At the same time I will demonstrate that, far from simply being the province of the survival horror genre, the zombie appears across an array of game forms, game cultures and game productions. The zombie highlights the participatory nature of game culture in the array of zombie 'mods' that users create to transform existing games into zombie based games, in particular in relation to titles such as the Call of Duty series. At the other end of the production spectrum the zombie features heavily in the little studied area of online flash games where the zombie can be found in a variety of game genres and forms. The zombie here often operates as a pastiche of popular zombie narratives in survival games (The Last Stand), parodic engagements with zombie conventions (Jetpacks and Zombies) or play with the notion of zombie pandemics (the Infectionator games). Here I situate the zombie game as a aesthetic genre that works to provide an easily understandable context for such interactive genres as survival horror, text adventures, shooting games, physics games and driving games, with the popularity of these enough to drive numerous dedicated hosting and link sites such as zombiegames.net. The pastiche element of these games extends into gamers social engagement with games. Online debates over the the appropriate actions or preparation for a zombie holocaust are commonplace on the internet in such spaces as Zombieresearch.net. Whilst many of these sites feature decidedly tongue in cheek engagement with the notion of the zombie apocalypse, the users of fora for games like Left 4 Dead and Dead Island tend to debate this directly in the terms of the games themselves, discussing their relative merits or realism. Some of these games also highlight the specific pleasures of identifying the zombie as protagonist of sorts. In discussing this I will return to online gaming and the Left 4 Dead games in which players may compete online as part of the zombie horde. Such games raise major questions for the issues of identification and immersion that are said to be at the centre of the game experience. I will also explore the parodic pleasures of many flash games that situate the player in the role of spreading zombie infections. Throughout this article I aim to demonstrate that the zombie in game culture is less a cultural metaphor than a combination of utilitarian antagonist and a persistent aesthetic; a means of providing style or pleasure to many games that relies on the intertextual and flexible nature of the zombie as popular cultural phenomenon

A concept for seeing-limited near-IR spectroscopy on the Giant Magellan Telescope

We present a simple seeing-limited IR spectrometer design for the Giant Magellan Telescope, with continuous R = 6000 coverage from 0.87-2.50 microns for a 0:7” slit. The instrument's design is based on an asymmetric white pupil echelle layout, with dichroics splitting the optical train into yJ, H, and K channels after the pupil transfer mirror. A separate low-dispersion mode offers single-object R ~ 850 spectra which also cover the full NIR bandpass in each exposure. Catalog gratings and H2RG detectors are used to minimize cost, and only two cryogenic rotary mechanisms are employed, reducing mechanical complexity. The instrument dewar occupies an envelope of 1:8×1:5×1:2 meters, satisfying mass and volume requirements for GMT with comfortable margin. We estimate the system throughput at ~ 35% including losses from the atmosphere, telescope, and instrument (i.e. all coatings, gratings, and sensors). This optical efficiency is comparable to the FIRE spectrograph on Magellan, and we have specified and designed fast cameras so the GMT instrument will have an almost identical pixel scale as FIRE. On the 6.5 meter Magellan telescopes, FIRE is read-noise limited in the y and J bands, similar to other existing near-IR spectrometers and also to JWST/NIRSPEC. GMT's twelve-fold increase in collecting area will therefore offer gains in signal-to-noise per exposure that exceed those of moderate resolution optical instruments, which are already sky-noise limited on today's telescopes. Such an instrument would allow GMT to pursue key early science programs on the Epoch of Reionization, galaxy formation, transient astronomy, and obscured star formation environments prior to commissioning of its adaptive optics system. This design study demonstrates the feasibility of developing relatively affordable spectrometers at the ELT scale, in response to the pressures of joint funding for these telescopes and their associated instrument suites.Massachusetts Institute of Technology. Department of Physics.Kavli Institute for Astrophysics and Space Researc