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Sharp-Rejection, Wide and Deep Stopband Low Pass Filter Design Using Open Stubs and DGS Patterns

100%
Challal M., Boulakroune M.
Acta Physica Polonica A
|
2016
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vol. 130
|
issue 1
9-10
EN
A sharp rejection, wide and deep stopband microstrip low pass filter is investigated in this paper. The proposed low pass filter is composed of three defected ground structure patterns and four open stubs. Simulated results verify that the filter has a sharpness factor of 0.9, a low insertion loss of 0.65 and a return loss less than 15 dB. Moreover, a wide stopband at 20 dB rejection ranging from 4.55 GHz to 11.62 GHz is accomplished. The filter presented in this work was compared with the previous works completed on low pass filter with sharp rejection. It has shown that the filter provides good performances in terms of sharp rejection, wide and deep rejection band and small passband insertion loss compared to those reported in the literatures.
2
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Bosons and Magnons in Ordered Magnets

100%
Köbler U.
Acta Physica Polonica A
|
2015
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vol. 127
|
issue 6
1694-1702
EN
In earlier experimental studies we have shown that in accordance with the principles of renormalization group theory the spin dynamics of ordered magnets is controlled by a boson guiding field instead by exchange interactions between nearest magnetic neighbors. In particular, thermal decrease of the magnetic order parameter is given by the heat capacity of the boson field. The typical signature of boson dynamics is that the critical power functions either at T=T_{c} or at T=0 hold up to a considerable distance from critical temperature. The critical power functions of the atomistic models hold asymptotically at T=T_{c} or at T=0 only. In contrast to the atomistic magnons field bosons cannot directly be observed using inelastic neutron scattering. However, for some classes of magnets the field bosons seem to have magnetic moment and thus are able to interact directly with magnons. This interaction, although weak in principle, leads to surprisingly strong functional modifications in the magnon dispersions at small q-values. In particular, the magnon excitation gap seems to be due to the magnon-boson interaction. In this communication we want to show that for small q-values the continuous part of the magnon dispersions can be fitted over a finite q-range by a power function of wave vector. The power function can be identified with the dispersion of the field bosons. It appears that for low q-values magnon dispersions get attracted by the boson dispersion and assume the dispersion of the bosons. This allows for an experimental evaluation of the boson dispersions from the known magnon dispersions. Exponent values of 1, 1.25, 1.5, and 2 have been identified. The boson dispersion relations and the associated power functions of temperature for the heat capacity of the boson fields are now empirically known for all dimensions of the field and for magnets with integer and half-integer spin quantum number. These are two 2× 3 exponent schemes.
3
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Relation of Gutzwiller Variational State with Matrix Model

88%
Koper A., Mucha M.
Acta Physica Polonica A
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1997
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vol. 91
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issue 2
391-394
EN
It is shown that mean values of electron operators in variational Gutzwiller state are equal to mean values of corresponding classical quantities calculated by means of a hermitian matrix model. In cases with small number of electrons in the system this property enables exact calculation of the mean values. In case of large number of electrons a simple and effective Monte Carlo method is formulated (within matrix model).
4
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Quantum states with Space-like energy-momentum

75%
Solomon D.
Open Physics
|
2006
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vol. 4
|
issue 3
380-392
EN
A common assumption in quantum field theory is that the energy-momentum 4-vector of any quantum state must be time-like. It will be proven that this is not the case for a Dirac-Maxwell field. In this case quantum states can be shown to exist whose energy-momentum is space-like.
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