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121.
D. V. Balin V. A. Ganzha S. M. Kozlov E. M. Maev G. E. Petrov M. A. Soroka G. N. Schapkin G. G. Semenchuk V. A. Trofimov A. A. Vasiliev A. A. Vorobyov N. I. Voropaev C. Petitjean B. Gartner B. Lauss J. Marton J. Zmeskal T. Case K. M. Crowe P. Kammel F. J. Hartmann M. P. Faifman 《Physics of Particles and Nuclei》2011,42(2):185-214
Muon catalyzed dd fusion in D2 and HD gases in the temperature range from 28 to 350 K was investigated in a series of experiments based on a time-projection ionization chamber operating with pure hydrogen. All main observables in this reaction chain were measured with high absolute precision including the resonant and non-resonant ddμ formation rates, the rate for hyperfine transitions in dμ atoms, the branching ratio of the two charge symmetric fusion channels 3He + n and t + p and the muon sticking probability. The report presents the final analysis of the data together with a comprehensive comparison with calculations based on recent μCF theories. The energy of the loosely bound ddμ state with quantum numbers J = 1, ν = 1, which is central to the mechanism of resonant molecule formation, is extracted with precision ?11(fit) = ?1.9651(7) eV. in impressive agreement with the latest theoretical results ?11(theory) = ?1.9646 eV. 相似文献
122.
J. Walter C. Hartmann J. H. Maddocks 《The European physical journal. Special topics》2011,200(1):153-181
The most classic approach to the dynamics of an n-dimensional mechanical system constrained by d independent holonomic constraints is to pick explicitly a new set of (n − d) curvilinear coordinatesparametrizingthe manifold of configurations satisfying the constraints, and to compute the Lagrangian
generating the unconstrained dynamics in these (n − d) configuration coordinates. Starting from this Lagrangian an unconstrained Hamiltonian H(q,p) on 2(n−d) dimensional phase space can then typically be defined in the standard way via a Legendre transform. Furthermore, if the
system is in contact with a heat bath, the associated Langevin and Fokker-Planck equations can be introduced. Provided that
an appropriate fluctuation-dissipation condition is satisfied, there will be a canonical equilibrium distribution of the Gibbs
form exp(−βH) with respect to the flat measure dqdp in these 2(n − d) dimensional curvilinear phase space coordinates. The existence of (n − d) coordinates satisfying the constraints is often guaranteed locally by an implicit function theorem. Nevertheless in many
examples these coordinates cannot be constructed in any tractable form, even locally, so that other approaches are of interest.
In ambient space formulations the dynamics are defined in the full original n-dimensional configuration space, and associated 2n-dimensional phase space, with some version of Lagrange multipliers introduced so that the 2(n − d) dimensional sub-manifold of phase space implied by the holonomic constraints and their time derivative, is invariant under
the dynamics. In this article we review ambient space formulations, and explain that for constrained dynamics there is in
fact considerable freedom in how a Hamiltonian form of the dynamics can be constructed. We then discuss and contrast the Langevin
and Fokker-Planck equations and their equilibrium distributions for the different forms of ambient space dynamics. 相似文献
123.
C. Hartmann J. C. Latorre G. Ciccotti 《The European physical journal. Special topics》2011,200(1):73-89
The aim of this mini-review article is to clarify the relation between two distinct formulations of the thermodynamic free
energy for collective variables which can be found in the molecular dynamics literature. In doing so, we discuss the different
ensemble concepts underlying the two definitions and reveal their relation to strong confinement (restraints) and molecular
constraints. The latter analysis is based on a variant of Federer’s coarea formula which can be regarded as a generalization
of Fubini’s theorem for iterated integrals to curvilinear coordinates and which implies the famous “blue moon” ensemble identity
for computing conditional expectations using constrained simulations. For illustration we will present a few paradigmatic
examples. 相似文献
124.
Carmen Sguazzo Mohamed Harhash Matthias Grafenhorst Heinz Palkowski Stefan Hartmann 《PAMM》2014,14(1):245-246
Composite materials are widely used in different industrial fields, because of their good formability and their high strength to weight ratio. In the present work a triple-layered sandwich composite is investigated. Experimental tests at room temperature are carried out for the materials constituting the composite. A finite element model of a deep-drawing process of the composite is performed, where a finite strain constitutive model for the metal part, with material parameters calibrated to uniaxial tensile tests, has been implemented. Experimental results are compared to the numerical simulations in view of validation purposes. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
125.
Field-assisted sintering technology (FAST) is a combined thermal and mechanical loading process to compact and sinter a powder material within one process step. In this short essay a constitutive model of thermo-viscoplasticity is proposed representing most of the phenomena observed in the experiments. The constitutive model is calibrated to the experimental data and some predicted experiments are compared with constitutive model showing appropriate results. (© 2014 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim) 相似文献
126.
We develop a new form of patching that is both far-reaching and more elementary than the previous versions that have been
used in inverse Galois theory for function fields of curves. A key point of our approach is to work with fields and vector
spaces, rather than rings and modules. After presenting a self-contained development of this form of patching, we obtain applications
to other structures such as Brauer groups and differential modules. 相似文献
127.
The reinitialization, which is required to regularize the level set function, can be computationally expensive and hence is a determining factor for the overall efficiency of a level set method. However, it often has a significantly adverse impact on the accuracy of the level set solution. This short note is meant to shed light on the efficiency and accuracy issues of the reinitialization process. Using just one clearly defined level set propagation test case with an analytical solution the solutions obtained using a recently proposed efficient lower‐order constrained reinitialization (CR) scheme and standard low‐ and high‐order reinitialization schemes are juxtaposed to evidence the superiority of the novel CR formulation. It is shown that maintaining the location of the zero level set during the reinitialization is crucial for the accuracy and that the displacement caused by standard high‐order reinitialization schemes clearly outweighs the benefit of the high‐order smoothing of the level set function. Finally, results of a three‐dimensional problem are concisely reported to demonstrate the general applicability of the CR scheme. Copyright © 2009 John Wiley & Sons, Ltd. 相似文献
128.
G. M. Kalvius L. Asch D. R. Noakes R. Keitel J. H. Brewer E. J. Ansaldo F. J. Litterst B. Boucher J. Chappert A. Yaouanc T. Yamazaki K. Nagamine K. Nishiyama O. Hartmann R. Wäppling 《Hyperfine Interactions》1986,31(1-4):303-308
Crystalline (cr-) Dyag [CsC] structure] orders antiferro-magnetically with TN≅60K; amorphous (am-) DyAg ferro-magnetically with TC≈-18K. We measured the longitudinal field (LF) μ+SR relaxation functions GZZ(t) for 5K<T<300K using surface muons. In the paramagnetic state. cr-DyAg gives an exponential GZZ (t) in the relaxation rate rising first slowly then more rapidlynear TN; no decoupling is observed in LF up to 0.4T. In the ordered state we see a Lorentzian Kubo-Toyabe GZZ(t), becoming nearly static at the lowest temperatures. Its static width is very narrow (Δ≈-7 MHz), and full dceoupling is
achieved here in 0.1 T. On approaching TN, the fluctuation rate and the static width increase mootonically bt the field distribution remains Loratzian. A LF of 0.4T
is then insufficient to quench the fast exponential relaxation. In paramagnetic am-DyAg, the μ+ depolarization is always much faster then in cr-DyAg. At lower temperatures it is better described by a root-exponential
than an exponential GZZ(t). Below TC an exponentially relaxing signal with 1/3 amplitude is seen. The decoupling effect of LF up to 0.4T was negligible at all
temperatures. 相似文献
129.
We define permutation modules and Young modules for the Brauer algebra B
k
(r,δ), and show that if the characteristic of the field k is neither 2 nor 3 then every permutation module is a sum of Young modules, respecting an ordering condition similar to that
for symmetric groups. Moreover, we determine precisely in which cases cell module filtration multiplicities are well-defined,
as done by Hemmer and Nakano for symmetric groups.
Supported by the European Community through Marie Curie fellowship MCFI 2002-01325
Supported by EPSRC grant GR/S18151/01 相似文献
130.
Hartmann F. J. Daniel H. Maierl Chr Mühlbauer M. Schott W. Wojciechowski P. Hauser P. Petitjean C. Taqqu D. Kottmann F. Markushin V. E. 《Hyperfine Interactions》1996,101(1):623-632
Two experiments with low-energy muons are described: the determination of the stopping power of C, Si, Ti and Au for muons at energies down to 2 keV and the measurement of the diffusion times for pµ and dµ atoms in low-pressure (0.25–12 hPa) hydrogen gas. A pronounced Barkas effect was found for muons at the Bragg peak (about 10 keV): the stopping power for µ– in C, e.g., is about 30% lower than that for µ+. The mean kinetic energy of pµ atoms at the end of the cascade in 1 hPa hydrogen gas was determined to be (2.6 ± 0.6) eV (preliminary value). 相似文献