14,862 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
First Evaluation of Dynamic Aperture at Injection for FCC-hh
In the Hadron machine option, proposed in the context of the Future Circular
Colliders (FCC) study, the dipole field quality is expected to play an
important role, as in the LHC. A preliminary evaluation of the field quality of
dipoles, based on the NbSn technology, has been provided by the magnet
group. The effect of these field imperfections on the dynamic aperture, using
the present lattice design, is presented and first tolerances on the b and
b multipole components are evaluated
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
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
A Vector Network Analyzer Based on Pulse Generators
A fast four channel network analyzer is introduced to measure <i>S</i>-parameters in a frequency range from 10MHz to 3GHz. The signal generation for this kind of analyzer is based on pulse generators, which are realized with bipolar transistors. The output signal of the transistor is differentiated and two short pulses, a slow and a fast one, with opposite polarities are generated. The slow pulse is suppressed with a clipping network. Thus the generation of very short electrical pulses with a duration of about 100ps is possible. The structure of the following network analyzer is similar to the structure of a conventional four channel network analyzer. </p><p style="line-height: 20px;"> All four pulses, which contain the high frequency information of the device under test, are evaluated after the digitalization of intermediate frequencies. These intermediate frequencies are generated with sampling mixers. The recorded data is evaluated with a special analysis technique, which is based on a Fourier transformation. </p><p style="line-height: 20px;"> The calibration techniques used are the same as for conventional four channel network analyzers, no new calibration techniques need to be developed
Semiregular Polytopes and Amalgamated C-groups
In the classical setting, a convex polytope is said to be semiregular if its
facets are regular and its symmetry group is transitive on vertices. This paper
studies semiregular abstract polytopes, which have abstract regular facets,
still with combinatorial automorphism group transitive on vertices. We analyze
the structure of the automorphism group, focusing in particular on polytopes
with two kinds of regular facets occurring in an "alternating" fashion. In
particular we use group amalgamations to prove that given two compatible
n-polytopes P and Q, there exists a universal abstract semiregular
(n+1)-polytope which is obtained by "freely" assembling alternate copies of P
and Q. We also employ modular reduction techniques to construct finite
semiregular polytopes from reflection groups over finite fields.Comment: Advances in Mathematics (to appear, 28 pages
- …