315 research outputs found
Graph topology and gap topology for unstable plants
This paper provides a refonnulation of the graph topology and the gap topology in a very general setting in the frequency domain. Many essential properties and their comparison are clearly presented in the refonnulation. It is shown that the gap topology is suitable for the general systems rather than square systems with unit feedback, which is the situation studied in [2,3,9]. It is also revealed that, whenever an unstable plant can be stabilized by a feedback, it is a closed operator, mapping input space to output space. Hence the gap topology can always be applied whenever the unstable plants can be stabilized. The graph topology and the gap topology are suitable for different unstable subsets, and have many similar characteristics. If one confines them to the same subset, they will be identical Finally, the definitions of the graph metric and the gap metric are discussed.
Keywords: graph topology, gap topology, unstable plants, feedback system
Sufficient conditions for BIBO robust stabilization : given by the gap metric
A relation between coprlme fractions and the gap metric is presented. Using this result we provide some sufficient conditions for BIBO robust stabilization for a very wide class of systems. These conditions allow the plant and compensator to be disturbed simultaneously. Keywords: Robust stabllization; Gap metric; Coprime fraction
Chirality in odd- nucleus Nd in particle rotor model
A particle rotor model is developed which couples several valence protons and
neutrons to a rigid triaxial rotor core. It is applied to investigating the
chirality in odd- nucleus Nd with configuration for the first time in a fully quantal approach.
For the two chiral sister bands, the observed energies and the and
values for the in-band as well as interband transitions are reproduced
excellently. Root mean square values of the angular momentum components and
their probability distributions are used for discussing in detail the chiral
geometry of the aplanar rotation and its evolution with angular momentum.
Chirality is found to change from a soft chiral vibration to nearly static
chirality at spin and back to another type of chiral vibration at
higher spin.Comment: 16 pages, 5 figure
Effect of the SiC Particle Orientation Anisotropy on the Tensile Properties of a Spray-Formed SiCp/Al-Si Composite
The effects of the SiC particle orientation anisotropy
on the tensile properties of spray-formed
SiCp/Al-Si composites was investigated and
compared with that of the unreinforced matrix alloy.
The addition of SiC particles increased the
elastic modulus but decreased ultimate tensile
strength and elongation of an Al–Si alloy under
peak-aged conditions. Microstructure disolayed a
preferred orientation of the reinforcement particles,
which were inclined to align parallel to the
extrusion axis. Meanwhile, the degree of orientation
anisotropy turned to be higher with larger reinforcement
sizes particle. The elastic modulus,
tensile strength and elongation in the longitudinal
orientation (parallel to the extrusion axis) were
higher than those in the transverse orientation
(perpendicular to the extrusion axis). The fracture
mechanism in a composite with 4.5 m particles
was attributed to interfacial debonding
between SiC and matrix in the two orientations.
However, in case of aluminum reinforced wild
20 m particles, both cracking of SiC particles in
the longitudinal orientation and the interfacial
debonding in the transverse orientation played an
important role in fracture.Исследовано влияние анизотропии, определяемой ориентацией SiC частиц, на механические
свойства при растяжении SiCp/Al-Si композита, полученного методом напыления. Результаты
исследования SiCp/Al-Si композита сопоставлены с таковыми сплава с неупрочненной матрицей. При растяжении Аl-Si сплава в условиях максимального старения благодаря введению SiC
частиц модуль упругости увеличивается, а предел прочности и удлинение уменьшаются. При
определении характеристик микроструктуры было установлено, что упрочняющие частицы
преимущественно ориентированы в направлении, параллельном оси экструзии. При значительном упрочнении степень анизотропии, определяемой ориентацией частиц, более высокая.
Значения модуля упругости, предела прочности и удлинения при растяжении в продольном
направлении (параллельно оси экструзии) оказываются выше, чем в поперечном (перпендикулярно оси экструзии). Признаком механизма разрушения композита с частицами размером
4,5 мкм полагают граничное разделение между SiC частицами и матрицей в двух направлениях. В случае упрочненного алюминия с частицами размером 20 мкм растрескивание SiC
частиц в продольном направлении и граничное разделение в поперечном направлении играют
важную роль в процессе разрушения.Досліджено вплив анізотропії, що визначається орієнтацією SiC частинок, на механічні властивості при розтязі SiCp/Al-Si композита, отриманого методом напилення.
Результати дослідження SiCp/Al-Si композита зіставляли з такими сплава, що має
незміцнювану матрицю. При розтязі Al-Si сплаву в умовах максимального старіння
завдяки введенно SiC частинок модуль пружності збільшується, а границя міцності і
подовження зменшуються. Визначення характеристик мікроструктури показало, що
зміцнювані частинки переважно орієнтовані у напрямку, паралельному осі екструзії.
При значному зміцненні ступінь анізотропії, що визначається орієнтацією частинок,
значно вища. Значення модуля пружності, границі міцності і подовження при розтязі
в поздовжньому напрямку (паралельно осі екструзії) більші, аніж у поперечному
(перпендикулярно до осі екструзії). Ознакою механізму руйнування композита з
частинками розміром 4,5 мкм вважають граничний розподіл між SiC частинками і
матрицею у двох напрямках. У випадку зміцненого алюмінію з частинками розміром
20 мкм розтріскування SiC частинок у поздовжньому напрямку і граничний розподіл
у поперечному напрямку відіграють важливу роль у процесі руйнування
Wigner Crystals Phases in Bilayer Quantum Hall Systems
(This is a substantially shortened version of the original abstract:)
The Wigner crystal phase diagram of the bilayer systems have been studied
using variational methods. Five crystal phases are obtained. As the layer
spacing increases, the system will undergo a sequence of phase transitions. A
common feature of most bilayer Wigner crystals is that they have mixed
(pseudo-spin) ferromagnetic and antiferromagnetic order.Comment: 19 figures. Figures will be provided upon request. Submitted in PRB
in Nov 94
Electron-electron interactions and two-dimensional - two-dimensional tunneling
We derive and evaluate expressions for the dc tunneling conductance between
interacting two-dimensional electron systems at non-zero temperature. The
possibility of using the dependence of the tunneling conductance on voltage and
temperature to determine the temperature-dependent electron-electron scattering
rate at the Fermi energy is discussed. The finite electronic lifetime produced
by electron-electron interactions is calculated as a function of temperature
for quasiparticles near the Fermi circle. Vertex corrections to the random
phase approximation substantially increase the electronic scattering rate. Our
results are in an excellent quantitative agreement with experiment.Comment: Revtex style, 21 pages and 8 postscript figures in a separate file;
Phys. Rev. B (in press
Anomaly analysis of Hawking radiation from Kaluza-Klein black hole with squashed horizon
Considering gravitational and gauge anomalies at the horizon, a new method
that to derive Hawking radiations from black holes has been developed by
Wilczek et al. In this paper, we apply this method to non-rotating and rotating
Kaluza-Klein black holes with squashed horizon, respectively. For the rotating
case, we found that, after the dimensional reduction, an effective U(1) gauge
field is generated by an angular isometry. The results show that the gauge
current and energy-momentum tensor fluxes are exactly equivalent to Hawking
radiation from the event horizon.Comment: 15 pages, no figures, the improved version, accepted by Eur. Phys. J.
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