40 research outputs found
Failure analysis of destructive coils
The failure of the destructive pulsed power coils has been investigated. The destructive coil is the key element of the laboratory system which generates half-period abrupt magnetic field pulses with the amplitudes up to 45 T. The transient coupled non-linear magneto-mechanical model has been applied for finite element simulations. The mechanical behavior and operation threshold of the coil have been examined. It has been found that operation threshold of the coil with relatively thin cylindrical reinforcement could be characterized by the opening of the plastic hinge and estimated numerically. Good agreement with experimental results has been observe
Failure analysis of destructive coils
The failure of the destructive pulsed power coils has been investigated. The destructive coil is the key element of the laboratory system which generates half-period abrupt magnetic field pulses with the amplitudes up to 45 T. The transient coupled non-linear magneto-mechanical model has been applied for finite element simulations. The mechanical behavior and operation threshold of the coil have been examined. It has been found that operation threshold of the coil with relatively thin cylindrical reinforcement could be characterized by the opening of the plastic hinge and estimated numerically. Good agreement with experimental results has been observe
Failure analysis of destructive coils
The failure of the destructive pulsed power coils has been investigated. The destructive coil is the key element of the laboratory system which generates half-period abrupt magnetic field pulses with the amplitudes up to 45 T. The transient coupled non-linear magneto-mechanical model has been applied for finite element simulations. The mechanical behavior and operation threshold of the coil have been examined. It has been found that operation threshold of the coil with relatively thin cylindrical reinforcement could be characterized by the opening of the plastic hinge and estimated numerically. Good agreement with experimental results has been observe
Ising Universality in Three Dimensions: A Monte Carlo Study
We investigate three Ising models on the simple cubic lattice by means of
Monte Carlo methods and finite-size scaling. These models are the spin-1/2
Ising model with nearest-neighbor interactions, a spin-1/2 model with
nearest-neighbor and third-neighbor interactions, and a spin-1 model with
nearest-neighbor interactions. The results are in accurate agreement with the
hypothesis of universality. Analysis of the finite-size scaling behavior
reveals corrections beyond those caused by the leading irrelevant scaling
field. We find that the correction-to-scaling amplitudes are strongly dependent
on the introduction of further-neighbor interactions or a third spin state. In
a spin-1 Ising model, these corrections appear to be very small. This is very
helpful for the determination of the universal constants of the Ising model.
The renormalization exponents of the Ising model are determined as y_t = 1.587
(2), y_h = 2.4815 (15) and y_i = -0.82 (6). The universal ratio Q =
^2/ is equal to 0.6233 (4) for periodic systems with cubic symmetry.
The critical point of the nearest-neighbor spin-1/2 model is K_c=0.2216546
(10).Comment: 25 pages, uuencoded compressed PostScript file (to appear in Journal
of Physics A
Improved high-temperature expansion and critical equation of state of three-dimensional Ising-like systems
High-temperature series are computed for a generalized Ising model with
arbitrary potential. Two specific ``improved'' potentials (suppressing leading
scaling corrections) are selected by Monte Carlo computation. Critical
exponents are extracted from high-temperature series specialized to improved
potentials, achieving high accuracy; our best estimates are:
, , , ,
. By the same technique, the coefficients of the small-field
expansion for the effective potential (Helmholtz free energy) are computed.
These results are applied to the construction of parametric representations of
the critical equation of state. A systematic approximation scheme, based on a
global stationarity condition, is introduced (the lowest-order approximation
reproduces the linear parametric model). This scheme is used for an accurate
determination of universal ratios of amplitudes. A comparison with other
theoretical and experimental determinations of universal quantities is
presented.Comment: 65 pages, 1 figure, revtex. New Monte Carlo data by Hasenbusch
enabled us to improve the determination of the critical exponents and of the
equation of state. The discussion of several topics was improved and the
bibliography was update
Magnetic relaxation in La0.250Pr0.375Ca0.375MnO3 with varying phase separation
We have studied the magnetic relaxation properties of the phase-separated
manganite compound La0.250Pr0.375Ca0.375MnO3 . A series of polycrystalline
samples was prepared with different sintering temperatures, resulting in a
continuous variation of phase fraction between metallic (ferromagnetic) and
charge-ordered phases at low temperatures. Measurements of the magnetic
viscosity show a temperature and field dependence which can be correlated to
the static properties. Common to all the samples, there appears to be two types
of relaxation processes - at low fields associated with the reorientation of
ferromagnetic domains and at higher fields associated with the transformation
between ferromagnetic and non-ferromagnetic phases.Comment: 30 pages with figures, PDF, accepted to be published in Physical
Review
Highly Local Measurements of Strong Transient Magnetic Fields During Railgun Experiments Using CMR-Based Sensors
FTIR/PCA study of propanol in argon matrix: The initial stage of clustering and conformational transitions
FTIR spectra of 1-propanol in an argon matrix were studied in the range 11 to 30 K. Principal component
analysis of dynamic FTIR spectra and nonlinear band shape fitting has been carried out. The peaks of monomer,
open dimer, mixed propanol-water dimer and those of higher H-bond clusters have been resolved and analyzed.
The attribution of certain FTIR peaks has been supported by proper density functional theory calculations. Analyzing
dependences of the integral band intensities of various aggregates on temperature it has been deduced that
in the initial stage of clustering monomers and dimers are the basic building blocks forming higher H-bond clusters.
The peaks assigned to two conformers of monomers and mixed propanol-water dimers were investigated
processing the temperature dependences of their integral intensities in Arrhenius plot. The obtained values of
0.18 kJ⋅mol⁻¹ for propanol monomer and 0.26 kJ⋅mol⁻¹ for mixed dimer are well comparable with the energy
differences between the global minimum conformation of 1-propanol (Gt) and some other energetically higher
structures (Tt or Tg)
Distributed laboratory system for characterization of current distribution in electromagnetic rail launchers
This paper presents the activity of a Distributed Measurement Laboratory on a challenging topic: the characterization of current distribution in electromagnetic rail launchers. Such experiments are characterized by strong transient magnetic fields, very fast moving conductors and the use of pulsed power in the GW range. Due to the high complexity of the investigated phenomenon an international network of laboratories is seen as an appropriate approach. The development of a proper network technology and a common platform is an important aspect to make the distributed measurement system efficient. Currently, various European laboratories have formed the European Pulsed Power Laboratories (EPPL) in order to improve their individual capacities and to develop networking measurement systems in the field of pulsed power R&D
Ultra-fast fault current limiter based on La-Ca-MnO3 thin films
A fast fault current limiter based on La0.67Ca0.33MnO3 films and designed in the shape of a co-planar 50 Ω impedance transmission line is presented. The limiter is intended to protect the input circuits of high frequency wide band electronic devices. The operation of this limiter is based on fast electroresistance phenomenon in manganites. The main behaviour of this phenomenon at temperatures close to its phase transition temperature Tm was studied. It was demonstrated that the specific resistance of the film decreases exponentially with increase of electric field. The experimental results of losses induced by the fault current limiter in a 50 Ω impedence transmission line for non-limiting and limiting regimes are presented. The phenomenological relation between input and output voltage transients' amplitudes of transmission lines protected by such limiter is obtained