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

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

Testing the Higgs Mechanism in the Lepton Sector with multi-TeV e+e- Collisions

Multi-TeV e+e- collisions provide with a large enough sample of Higgs bosons to enable measurements of its suppressed decays. Results of a detailed study of the determination of the muon Yukawa coupling at 3 TeV, based on full detector simulation and event reconstruction, are presented. The muon Yukawa coupling can be determined with a relative accuracy of 0.04 to 0.08 for Higgs bosons masses from 120 GeV to 150 GeV, with an integrated luminosity of 5 inverse-ab. The result is not affected by overlapping two-photon background.Comment: 6 pages, 2 figures, submitted to J Phys G.: Nucl. Phy

The CLIC Programme: Towards a Staged e+e- Linear Collider Exploring the Terascale : CLIC Conceptual Design Report

This report describes the exploration of fundamental questions in particle physics at the energy frontier with a future TeV-scale e+e- linear collider based on the Compact Linear Collider (CLIC) two-beam acceleration technology. A high-luminosity high-energy e+e- collider allows for the exploration of Standard Model physics, such as precise measurements of the Higgs, top and gauge sectors, as well as for a multitude of searches for New Physics, either through direct discovery or indirectly, via high-precision observables. Given the current state of knowledge, following the observation of a 125 GeV Higgs-like particle at the LHC, and pending further LHC results at 8 TeV and 14 TeV, a linear e+e- collider built and operated in centre-of-mass energy stages from a few-hundred GeV up to a few TeV will be an ideal physics exploration tool, complementing the LHC. In this document, an overview of the physics potential of CLIC is given. Two example scenarios are presented for a CLIC accelerator built in three main stages of 500 GeV, 1.4 (1.5) TeV, and 3 TeV, together with operating schemes that will make full use of the machine capacity to explore the physics. The accelerator design, construction, and performance are presented, as well as the layout and performance of the experiments. The proposed staging example is accompanied by cost estimates of the accelerator and detectors and by estimates of operating parameters, such as power consumption. The resulting physics potential and measurement precisions are illustrated through detector simulations under realistic beam conditions.Comment: 84 pages, published as CERN Yellow Report https://cdsweb.cern.ch/record/147522

Influence of Auditory Cues on the visually-induced Self-Motion Illusion (Circular Vection) in Virtual Reality

This study investigated whether the visually induced selfmotion illusion (“circular vection”) can be enhanced by adding a matching auditory cue (the sound of a fountain that is also visible in the visual stimulus). Twenty observers viewed rotating photorealistic pictures of a market place projected onto a curved projection screen (FOV: 54°x45°). Three conditions were randomized in a repeated measures within-subject design: No sound, mono sound, and spatialized sound using a generic head-related transfer function (HRTF). Adding mono sound increased convincingness ratings marginally, but did not affect any of the other measures of vection or presence. Spatializing the fountain sound, however, improved vection (convincingness and vection buildup time) and presence ratings significantly. Note that facilitation was found even though the visual stimulus was of high quality and realism, and known to be a powerful vection-inducing stimulus. Thus, HRTF-based auralization using headphones can be employed to improve visual VR simulations both in terms of self-motion perception and overall presence

Investigation of the Afterglow Mode with the Caprice ECRIS for the GSI Heavy-Ion-Synchrotron operation

The Caprice-type ECRIS of the High Charge State Injector (HLI) of GSI predominantly has been operated in DC mode so far to deliver high duty cycle beams for the experimental area of the LINAC (UNILAC). The increasing demand of the Heavy Ion Synchrotron (SIS) for high intensities of heavy ion beams at very low duty cycle favours the application of the afterglow mode by pulsed operation of the ECRIS in these cases. Experiments with O, Ar, Xe and mainly with Pb were performed at the new ECR injector setup (EIS) which is a copy of the HLI injection beam line. Different RF pulse lengths and repetition rates were compared to optimise the respective afterglow intensities. For Pb two different types of ovens were investigated and modifications of the extraction system were applied. Thus peak intensities in the afterglow for 208Pb27+ of up to 200 emA could be obtained. Stable operation for time periods of several days could be achieved at reduced intensity level. Operational experiences are reported under the aspect of adaptation to SIS injection

Advanced flight control system study

A fly by wire flight control system architecture designed for high reliability includes spare sensor and computer elements to permit safe dispatch with failed elements, thereby reducing unscheduled maintenance. A methodology capable of demonstrating that the architecture does achieve the predicted performance characteristics consists of a hierarchy of activities ranging from analytical calculations of system reliability and formal methods of software verification to iron bird testing followed by flight evaluation. Interfacing this architecture to the Lockheed S-3A aircraft for flight test is discussed. This testbed vehicle can be expanded to support flight experiments in advanced aerodynamics, electromechanical actuators, secondary power systems, flight management, new displays, and air traffic control concepts

Electronic structure of barium-doped C₆₀

We have investigated the electronic structure of Ba-doped C60 films with Ba concentrations of up to x≈12 (BaxC60) by applying valence-band photoemission and x-ray-absorption spectroscopy. A crystal orbital (CO) formalism based on a semiempirical Hamiltonian of the intermediate-neglect-of-differential-overlap type has been employed to derive solid-state results for the Ba-doped C60 fullerides. Using x-ray diffraction, we show three distinct phases for the bulk BaxC60 system with Ba concentrations of up to x=6. In all cases, the experimental observations strongly indicate that fulleride formation leads to the occupation of hybrid bands on both sides of the Fermi level. The theoretical data indicate that the alkaline-earth atoms are essentially monovalent and hybridize strongly with the π-type functions of the C60 network. The Ba atoms in the BaxC60 fullerides deviate from the limit of complete charge transfer as a consequence of the competition between covalent Ba-C60 bonding and ionic contributions. Furthermore, it is shown that the calculated density-of-state profiles reproduce the photoemission data in the extreme outer valence-band region

Electronic Structure of the C₆₀ Fragment in Alkali- and Alkaline-earth-doped Fullerides

The electronic structure of the C60 fragment in alkali- and alkaline-earth-doped fullerides is studied theoretically. With increasing metal-to-C60 charge transfer (CT) the n electronic properties of the soccerball are changed. In the undoped solid and for not too high a concentration of doping atoms the hexagon-hexagon (6-6) bonds show sizeable double bond character while the hexagon-pentagon (6-5) bonds are essentially of single bond type. In systems with a high concentration of doping atoms this relative ordering is changed. Now the 6-5 bonds have partial double bond character and the 6-6 bonds are essentially single bonds. The high ability of the C60 unit to accomodate excess electrons prevents any sizeable weakening of the overall n bonding in systems with up to 12 excess electrons on the soccerball. A crystal orbital (CO) formalism on the basis of an INDO (intermediate neglect of differential overlap) Hamiltonian has been employed to derive solid state results for potassium- and barium-doped C60 fullerides. For both types of doping atoms an incomplete metal-to-C60 CT is predicted. In the potassium-doped fullerides the magnitude of the CT depends on the interstitial site of the dopant. The solid state data have been supplemented by INDO and ab initio calculations on molecular C60, C6-60 and C12-60. The calculated bondlength alternation in the neutral molecule is changed in C12-60 where the length of the 6-6 bonds exceeds the length of the 6-5 bonds. The geometries of the three molecular species have been optimized with a 3-21 G* basis. The theoretically derived modification of the C60 (π) electronic structure as a function of the electron count is explained microscopically in the framework of two quantum statistics accessible for π electronic ensembles. In the π ensemble of the C60 fragment so-called hard core bosonic properties are maximized where the Pauli antisymmetry principle has the character of a hidden variable only. Here the electronic degrees of freedom are attenuated only by the Pauli exclusion principle. This behaviour leads to the changes in the π electronic structure mentioned above