918 resultados para collision attack
Effect of Freezing-Thawing Cycles on the Resistance of Self-Consolidating Concrete to Sulfate Attack
Resumo:
Sydney playwright Lachlan Philpott’s Bison (2000/2009) is immersed in a sweaty, summery Antipodean scene of bronzed and toned bodies. It is located in the flora and fauna of gum trees and biting ants. Yet, despite this, it could be argued that at its heart it is not a specifically Australian site, but an all-too translatable scene that seems to be played out in gay clubs, bars, chatrooms and saunas around the Western world: men repeating patterns, looking for sex or love; checking out bodies, craving perfection; avoiding, and occasionally seeking, disease. At least, that was my assumption when I decided to direct the play in Belfast, Northern Ireland, in 2009. Philpott came to Belfast to workshop the play with the actors and, as a group, we restructured the play and tried to find a way to ‘de-Australianise’ it without necessarily placing it in a new geographical place - Northern Ireland - through linguistic clues in the text. As Philpott put it: ‘Let’s not make this play about Belfast or Sydney or London or anywhere because it is not a fair reflection of these scenes. Maybe we should just identify the generic elements of this world and then make Bison a play that reflects gaytown – because the rituals are all the same in Western society’. The experience of doing the play in Belfast made clear, however, that ideas of a global gay identity/experience –though highly marketed – fail to account for the vastly different situations of embodied gay experience. And the Northern Irish gay experience, while it has imported the usual ‘generic’ tropes of gayness, sits within a specific cultural context in which the farsighted legislation on equality for gays (imposed by either London or the EU) vastly outstrips wider societal thinking. For many in Northern Ireland, erstwhile MP Iris Robinson’s comments about homosexuality being an ‘abomination’ were a reason to support her, rather than to reject her. For me, the comments were the catalyst to doing Bison in Belfast.
Resumo:
Lip separation is one of the primary sources of inlet distortion, which can result in a loss in fan stability. High angles of incidence are one of several critical causes of lip separation. There have been many studies into inlet performance at high incidence, including the resulting distortion levels when lip separation occurs. However, the vast majority of these investigations have been carried out experimentally, with little in the way of computational results for inlet performance at high incidence. The flow topology within an inlet when lip separation has occurred is also not well understood. This work aims to demonstrate a suitable model for the prediction of inlet flows at high incidence using ANSYS CFX, looking at both the performance of the inlet and the separated flow topology within the inlet. The attenuating effect of the fan is also investigated, with particular emphasis on the flow redistribution ahead of the fan. The results show that the model used is suitable for predicting inlet performance in adverse operating conditions, showing good agreement with experimental results. In addition, the attenuation of the distortion by the fan is also captured by the numerical model.
Resumo:
In this paper, we present collision strengths and Maxwellian averaged effective collision strengths for the electron-impact excitation of Ni II. Attention is expressly concentrated on the optically allowed fine-structure transitions between the 3d 9, 3d 84s, and 3d 74s 2 even parity levels and the 3d 84p and 3d 74s 4p odd parity levels. The parallel RMATRXII R-matrix package has been recently extended to allow for the inclusion of relativistic fine-structure effects. This suite of codes has been utilized in conjunction with the parallel PSTGF and PSTGICF programs in order to compute converged total collision strengths for the allowed transitions with which this study is concerned. All 113 LS terms identified with the 3d 9, 3d 84s, 3d 74s 2, 3d 84p, and 3d 74s 4p basis configurations were included in the target wavefunction representation, giving rise to a sophisticated 295 jj-level, 1930 coupled channel scattering complex. Maxwellian averaged effective collision strengths have been computed at 30 individual electron temperatures ranging from 30 to 1,000,000 K. This range comfortably encompasses all temperatures significant to astrophysical and plasma applications. The convergence of the collision strengths is exhaustively investigated and comparisons are made with previous theoretical works, where significant discrepancies exist for the majority of transitions. We conclude that intrinsic in achieving converged collision strengths and thus effective collision strengths for the allowed transitions is the combined inclusion of contributions from the (N + 1) partial waves extending to a total angular momentum value of L = 50 and further contributions from even higher partial waves accomplished by employing a "top-up" procedure.
Resumo:
The aim of this paper is to report the preliminary development of an automatic collision avoidance technique for unmanned marine craft based on standardised rules, COLREGs, defined by the International Maritime Organisation. It is noted that all marine surface vessels are required to adhere to COLREGs at all times in order to minimise or eliminate the risk of collisions. The approach presented is essentially a reactive path planning algorithm which provides feedback to the autopilot of an unmanned vessel or the human captain of a manned ship for steering the craft safely. The proposed strategy consists of waypoint guidance by line-of-sight coupled with a manual biasing scheme. This is applied to the dynamic model of an unmanned surface vehicle. A simple PID autopilot is incorporated to ensure that the vessel adheres to the generated seaway. It is shown through simulations that the resulting scheme is able to generate viable trajectories in the presence of both stationary and dynamic obstacles. Rules 8 and 14 of the COLREGs, which apply to the amount of manoeuvre and to a head-on scenario respectively are simulated. A comparison is also made with an offline or deliberative grid-based path planning algorithm which has been modified to generate COLREGs-compliant routes.
Resumo:
In this paper, we present electron-impact excitation collision strengths and Maxwellian averaged effective collision strengths for the complicated iron-peak ion Cr II. We consider specifically the allowed lines for transitions from the 3d(5) and 3d(4)4s even parity configuration states to the 3d(4)4p odd parity configuration levels. The parallel suite of R-Matrix packages, RMATRX II, which have recently been extended to allow for the inclusion of relativistic effects, were used to compute the collision cross sections. A total of 108 LS pi/280 J pi levels from the basis configurations 3d(5), 3d(4)4s, and 3d(4)4p were included in the wavefunction representation of the target including all doublet, quartet, and sextet terms. Configuration interaction and correlation effects were carefully considered by the inclusion of seven more configurations and a pseudo-corrector (4d) over bar type orbital. The 10 configurations incorporated into the Cr II model thus listed are 3d(5), 3d(4)4s, 3d(4)4p, 3d(3)4s(2), 3d(3)4p(2), 3d(3)4s4p, 3d(4)(4d) over bar, 3d(3)4s (4d) over bar, 3d(3)4p (4d) over bar, and 3d(3)(4d) over bar (2), constituting the largest Cr II target model considered to date in a scattering calculation. The Maxwellian averaged effective collision strengths are computed for a wide range of electron temperatures 2000-100,000 K which are astrophysically significant. Care has been taken to ensure that the partial wave contributions to the collision strengths for these allowed lines have converged with "top-up" from the Burgess-Tully sum rule incorporated. Comparisons are made with the results of Bautista et al. and significant differences are found for some of the optically allowed lines considered.
Resumo:
The Coulomb–Born approximation is used to calculate electron-impact excitation collision strengths and effective collision strengths for optically allowed transitions among degenerate fine-structure levels of hydrogenic ions with 2⩽Z⩽30 and n⩽5. Collision strengths are calculated over a wide range of energies up to View the MathML source. Effective collision strengths are obtained over a wide temperature range up to View the MathML source by integrating the collision strengths over a Maxwellian distribution of electron velocities.