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Mixed H2/H∞ filtering for uncertain systems with regional pole assignment
Copyright [2005] IEEE. This material is posted here with permission of the IEEE. Such permission of the IEEE does not in any way imply IEEE endorsement of any of Brunel University's products or services. Internal or personal use of this material is permitted. However, permission to reprint/republish this material for advertising or promotional purposes or for creating new collective works for resale or redistribution must be obtained from the IEEE by writing to [email protected]. By choosing to view this document, you agree to all provisions of the copyright laws protecting it.The mixed H2/H∞ filtering problem for uncertain linear continuous-time systems with regional pole assignment is considered. The purpose of the problem is to design an uncertainty-independent filter such that, for all admissible parameter uncertainties, the following filtering requirements are simultaneously satisfied: 1) the filtering process is asymptotically stable; 2) the poles of the filtering matrix are located inside a prescribed region that compasses the vertical strips, horizontal strips, disks, or conic sectors; 3) both the H2 norm and the H∞ norm on the respective transfer functions are not more than the specified upper bound constraints. We establish a general framework to solve the addressed multiobjective filtering problem completely. In particular, we derive necessary and sufficient conditions for the solvability of the problem in terms of a set of feasible linear matrix inequalities (LMIs). An illustrative example is given to illustrate the design procedures and performances of the proposed method
Gravitational collapse of magnetized clouds II. The role of Ohmic dissipation
We formulate the problem of magnetic field dissipation during the accretion
phase of low-mass star formation, and we carry out the first step of an
iterative solution procedure by assuming that the gas is in free-fall along
radial field lines. This so-called ``kinematic approximation'' ignores the back
reaction of the Lorentz force on the accretion flow. In quasi steady-state, and
assuming the resistivity coefficient to be spatially uniform, the problem is
analytically soluble in terms of Legendre's polynomials and confluent
hypergeometric functions. The dissipation of the magnetic field occurs inside a
region of radius inversely proportional to the mass of the central star (the
``Ohm radius''), where the magnetic field becomes asymptotically straight and
uniform. In our solution, the magnetic flux problem of star formation is
avoided because the magnetic flux dragged in the accreting protostar is always
zero. Our results imply that the effective resistivity of the infalling gas
must be higher by several orders of magnitude than the microscopic electric
resistivity, to avoid conflict with measurements of paleomagnetism in
meteorites and with the observed luminosity of regions of low-mass star
formation.Comment: 20 pages, 4 figures, The Astrophysical Journal, in pres
Does parents' socio-economic status matter in intentions of vaccinating against human papillomavirus for adolescent daughters?
Background: The Human Papilloma Virus (HPV) vaccination provides substantial protection, and it is best to be taken before the age of twelve. Taiwan approved HPV vaccines since 2006. However, very few female adolescent have been vaccinated until now.Objectives: To examine whether the parents’ socio-economic status matters in deciding to purchase HPV vaccination for their daughters based on the theory of planned behavior.Method: A structured questionnaire to collect 394 responses from parents of adolescent girls in Taiwan. Data was coded to categorize relevant socio-economic classes, and was analyzed with SPSS.Results: The behavior intentions of parents with low (mean= 5.28) and high (5.01) socio-economic status are significantly stronger than the moderate (4.56) in deciding to purchase the HPV vaccination. Socio-economic factor has a slightly negative impact (B= -0.08), and attitude (0.68), subjective norms (0.16), and behavior control (0.32) have positive impacts on the parents’ intention.Conclusion: Major impacts on the decision to purchase an HPV vaccination for their adolescent was not due to the parents’ socio-economic status but the parent’s attitude. As the major predictor of a less complicated decision, attitudes toward the HPV vaccination should be reinforced through continuous communications between service providers and patient-advocate groups.Keywords: Human Papillomavirus, cervical cancer, theory of planned behavior, vaccination, adolescen
The Effect of the Random Magnetic Field Component on the Parker Instability
The Parker instability is considered to play important roles in the evolution
of the interstellar medium. Most studies on the development of the instability
so far have been based on an initial equilibrium system with a uniform magnetic
field. However, the Galactic magnetic field possesses a random component in
addition to the mean uniform component, with comparable strength of the two
components. Parker and Jokipii have recently suggested that the random
component can suppress the growth of small wavelength perturbations. Here, we
extend their analysis by including gas pressure which was ignored in their
work, and study the stabilizing effect of the random component in the
interstellar gas with finite pressure. Following Parker and Jokipii, the
magnetic field is modeled as a mean azimuthal component, , plus a random
radial component, , where is a random function
of height from the equatorial plane. We show that for the observationally
suggested values of , the tension due to the random
component becomes important, so that the growth of the instability is either
significantly reduced or completely suppressed. When the instability still
works, the radial wavenumber of the most unstable mode is found to be zero.
That is, the instability is reduced to be effectively two-dimensional. We
discuss briefly the implications of our finding.Comment: 10 pages including 2 figures, to appear in The Astrophysical Journal
Letter
Quantum Information Approach to Bose-Einstein Condensate in a Tilted Double-Well System
We study the ground state properties of bosons in a tilted double-well
system. We use fidelity susceptibility to identify the possible ground state
transitions under different tilt values. For a very small tilt (for example
), two transitions are found. For a moderate tilt (for example
), only one transition is found. For a large tilt (for example
), no transition is found. We explain this by analyzing the spectrum
of the ground state. The quantum discord and total correlation of the ground
state under different tilts are also calculated to indicate those transitions.
In the transition region, both quantities have peaks decaying exponentially
with particle number . This means for a finite-size system the transition
region cannot be explained by the mean-field theory, but in the large- limit
it can be.Comment: 5 pages, 5 figures, slightly different from the published versio
The implementation of a lossless data compression module in an advanced orbiting system: Analysis and development
Data compression has been proposed for several flight missions as a means of either reducing on board mass data storage, increasing science data return through a bandwidth constrained channel, reducing TDRSS access time, or easing ground archival mass storage requirement. Several issues arise with the implementation of this technology. These include the requirement of a clean channel, onboard smoothing buffer, onboard processing hardware and on the algorithm itself, the adaptability to scene changes and maybe even versatility to the various mission types. This paper gives an overview of an ongoing effort being performed at Goddard Space Flight Center for implementing a lossless data compression scheme for space flight. We will provide analysis results on several data systems issues, the performance of the selected lossless compression scheme, the status of the hardware processor and current development plan
Branch, Spur, and Feather Formation in Spiral Galaxies
We use hydrodynamical simulations to investigate the response of
geometrically thin, self-gravitating, singular isothermal disks of gas to
imposed rigidly rotating spiral potentials. By minimizing reflection-induced
feedback from boundaries, and by restricting our attention to models where the
swing parameter , we minimize the swing amplification of global
normal modes even in models where Toomre's in the gas disk. We
perform two classes of simulations: short-term ones over a few galactic
revolutions where the background spiral forcing is large, and long-term ones
over many galactic revolutions where the spiral forcing is considerably
smaller. In both classes of simulations, the initial response of the gas disk
is smooth and mimics the driving spiral field. At late times, many of the
models evince substructure akin to the so-called branches, spurs, and feathers
observed in real spiral galaxies. We comment on the parts played respectively
by ultraharmonic resonances, reflection off internal features produced by
nonlinear dredging, and local, transient, gravitational instabilites within
spiral arms in the generation of such features. Our simulations reinforce the
idea that spiral structure in the gaseous component becomes increasingly
flocculent and disordered with the passage of time, even when the background
population of old disk stars is a grand-design spiral. We speculate that truly
chaotic behavior arises when many overlapping ultraharmonic resonances develop
in reaction to an imposed spiral forcing that has itself a nonlinear, yet
smooth, wave profile.Comment: Accepted for publication in Astrophysical Journal (tentatively
October 10, 2003). Version with higher resolution embedded postscript figures
at http://astron.berkeley.edu/~sukanya/ms.p
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