12,847 research outputs found
Beam-induced backgrounds in the CLIC 3 TeV CM energy interaction region
Luminosity spectrum and accelerator background levels strongly influence the
experimental conditions and have an important impact on detector design. The
expected rates of the main beam-beam products at CLIC 3 TeV CM energy, taking
into account for machine imperfections, are computed. Among the other
machine-induced background the photon fans from the Incoherent Synchrotron
Radiation (ISR) photons emitted in the final doublet are evaluated.Comment: Proceedings of LCWS1
An approach to metal fatigue
Cumulative fatigue damage based on investigation of fatigue limit associated with crack, crack propagation rate, and stress interaction cycle in metal
Regular Incidence Complexes, Polytopes, and C-Groups
Regular incidence complexes are combinatorial incidence structures
generalizing regular convex polytopes, regular complex polytopes, various types
of incidence geometries, and many other highly symmetric objects. The special
case of abstract regular polytopes has been well-studied. The paper describes
the combinatorial structure of a regular incidence complex in terms of a system
of distinguished generating subgroups of its automorphism group or a
flag-transitive subgroup. Then the groups admitting a flag-transitive action on
an incidence complex are characterized as generalized string C-groups. Further,
extensions of regular incidence complexes are studied, and certain incidence
complexes particularly close to abstract polytopes, called abstract polytope
complexes, are investigated.Comment: 24 pages; to appear in "Discrete Geometry and Symmetry", M. Conder,
A. Deza, and A. Ivic Weiss (eds), Springe
Optimal Control for Generating Quantum Gates in Open Dissipative Systems
Optimal control methods for implementing quantum modules with least amount of
relaxative loss are devised to give best approximations to unitary gates under
relaxation. The potential gain by optimal control using relaxation parameters
against time-optimal control is explored and exemplified in numerical and in
algebraic terms: it is the method of choice to govern quantum systems within
subspaces of weak relaxation whenever the drift Hamiltonian would otherwise
drive the system through fast decaying modes. In a standard model system
generalising decoherence-free subspaces to more realistic scenarios,
openGRAPE-derived controls realise a CNOT with fidelities beyond 95% instead of
at most 15% for a standard Trotter expansion. As additional benefit it requires
control fields orders of magnitude lower than the bang-bang decouplings in the
latter.Comment: largely expanded version, superseedes v1: 10 pages, 5 figure
Visually induced linear vection is enhanced by small physical accelerations
Wong & Frost (1981) showed that the onset latency of visually induced self-rotation illusions (circular vection) can be reduced by concomitant small physical motions (jerks). Here, we tested whether (a) such facilitation also applies for translations, and (b) whether the strength of the jerk (degree of visuo-vestibular cue conflict) matters. 14 naïve observers rated onset, intensity, and convincingness of forward linear vection induced by photorealistic visual stimuli of a street of houses presented on a projection screen (FOV: 75°×58°). For 2/3 of the trials, brief physical forward accelerations (jerks applied using a Stewart motion platform) accompanied the visual motion onset. Adding jerks enhanced vection significantly; Onset latency was reduced by 50, convincingness and intensity ratings increased by more than 60. Effect size was independent of visual acceleration (1.2 and 12m/s^2) and jerk size (about 0.8 and 1.6m/s^2 at participants head for 1 and 3cm displacement, respectively), and showed no interactions. Thus, quantitative matching between the visual and physical acceleration profiles might not be as critical as often believed as long as they match qualitatively and are temporally synchronized. These findings could be employed for improving the convincingness and effectiveness of low-cost simulators without the need for expensive, large motion platforms
Status report of the baseline collimation system of CLIC. Part II
Important efforts have recently been dedicated to the characterisation and
improvement of the design of the post-linac collimation system of the Compact
Linear Collider (CLIC). This system consists of two sections: one dedicated to
the collimation of off-energy particles and another one for betatron
collimation. The energy collimation system is further conceived as protection
system against damage by errant beams. In this respect, special attention is
paid to the optimisation of the energy collimator design. The material and the
physical parameters of the energy collimators are selected to withstand the
impact of an entire bunch train. Concerning the betatron collimation section,
different aspects of the design have been optimised: the transverse collimation
depths have been recalculated in order to reduce the collimator wakefield
effects while maintaining a good efficiency in cleaning the undesired beam
halo; the geometric design of the spoilers has been reviewed to minimise
wakefields; in addition, the optics design has been optimised to improve the
collimation efficiency. This report presents the current status of the the
post-linac collimation system of CLIC. Part II is mainly dedicated to the study
of the betatron collimation system and collimator wakefield effects.Comment: 25 pages, 13 figure
Language difficulties in first year Science
A key goal of the study entitled ‘A cross-disciplinary approach to language support for first year students in the science disciplines’, funded by the Carrick Institute for Learning and Teaching in Higher Education, is to examine the role of language in the learning of science by first-year university students. The disciplines involved are Physics, Chemistry and Biology. This national project also aims to transfer active learning skills, which are widely used in language teaching, to the teaching of science in first year. The paper discusses the background to the study, reports on some of the preliminary results on the language difficulties faced by first year student cohorts in science from data collected in 2008, and describes the framework we have established for the organization and delivery of first year science courses to be implemented in semester one 2009
Embedding in-discipline language support for first year students in the sciences
This paper reports on a project which aims at addressing the need to cater for the language needs of a diverse student body (both domestic and international student body) by embedding strategic approaches to learning and teaching in first year sciences in tertiary education. These strategies consist of active learning skills which are widely used in language learning. The disciplines covered by the project are Biology, Chemistry and Physics and involves the University of Canberra (UC), University of Sydney (USyd), University of Tasmania (UTAS), University of Technology, Sydney (UTS) and University of Newcastle (Newcastle) in Australia. This project is funded by the Australian Learning and Teaching Council (ALTC). The paper discusses the background to the study and reports on results on the language difficulties faced by first year science student cohorts from data collected in 2008 as well as qualitative data was also collected on 2008 students’ attitudes towards online science learning. It will also report on the results on the implementation of the learning strategies at UTS and UTAS in Physics and Chemistry disciplines in 2009. Keywords: First year science teaching, role of language in science teaching, active learning skill
Modelling and Measurement of Charge Transfer in Multiple GEM Structures
Measurements and numerical simulations on the charge transfer in Gas Electron
Multiplier (GEM) foils are presented and their implications for the usage of
GEM foils in Time Projection Chambers are discussed. A small test chamber has
been constructed and operated with up to three GEM foils. The charge transfer
parameters derived from the electrical currents monitored during the
irradiation with an Fe-55 source are compared with numerical simulations. The
performance in magnetic fields up to 2 T is also investigated.Comment: 21 pages, 16 figures, submitted to NIM-
- …