2,257 research outputs found
The Path Along the Ridge: Regional Planning in the Face of Uncertainty
The Northwest Power Act responds to the changing circumstances of electric power in the Pacific Northwest by defining policy directions and creating new institutional arrangements for regional power planning. The Northwest Power Planning Council (Council) is the agent of the region in meeting the challenges of planning under the Act. This paper discusses the conceptual framework of regional power planning—a task that confronts a degree of uncertainty and risk without historical precedent
Within the Hundredth Meridian: Western States and Their River Basins in a Time of Transition
29 pages.
Contains footnotes
Relation Between Quantum Speed Limits And Metrics On U(n)
Recently, Chau [Quant. Inform. & Comp. 11, 721 (2011)] found a family of
metrics and pseudo-metrics on -dimensional unitary operators that can be
interpreted as the minimum resources (given by certain tight quantum speed
limit bounds) needed to transform one unitary operator to another. This result
is closely related to the weighted -norm on . Here we
generalize this finding by showing that every weighted -norm on
with 1\le p \le \limitingp induces a metric and a
pseudo-metric on -dimensional unitary operators with quantum
information-theoretic meanings related to certain tight quantum speed limit
bounds. Besides, we investigate how far the correspondence between the
existence of metrics and pseudo-metrics of this type and the quantum speed
limits can go.Comment: minor amendments, 6 pages, to appear in J.Phys.
Pressure Correction in Density Functional Theory Calculations
First-principles calculations based on density functional theory have been
widely used in studies of the structural, thermoelastic, rheological, and
electronic properties of earth-forming materials. The exchange-correlation
term, however, is implemented based on various approximations, and this is
believed to be the main reason for discrepancies between experiments and
theoretical predictions. In this work, by using periclase MgO as a prototype
system we examine the discrepancies in pressure and Kohn-Sham energy that are
due to the choice of the exchange-correlation functional. For instance, we
choose local density approximation and generalized gradient approximation. We
perform extensive first-principles calculations at various temperatures and
volumes and find that the exchange-correlation-based discrepancies in Kohn-Sham
energy and pressure should be independent of temperature. This implies that the
physical quantities, such as the equation of states, heat capacity, and the
Gr\"{u}neisen parameter, estimated by a particular choice of
exchange-correlation functional can easily be transformed into those estimated
by another exchange-correlation functional. Our findings may be helpful in
providing useful constraints on mineral properties %at thermodynamic conditions
compatible to deep Earth. at deep Earth thermodynamic conditions
Book reviews
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/45440/1/11077_2004_Article_BF00136037.pd
Longitudinal spin transport in diluted magnetic semiconductor superlattices: the effect of the giant Zeeman splitting
Longitudinal spin transport in diluted magnetic semiconductor superlattices
is investigated theoretically. The longitudinal magnetoconductivity (MC) in
such systems exhibits an oscillating behavior as function of an external
magnetic field. In the weak magnetic field region the giant Zeeman splitting
plays a dominant role which leads to a large negative magnetoconductivity. In
the strong magnetic field region the MC exhibits deep dips with increasing
magnetic field. The oscillating behavior is attributed to the interplay between
the discrete Landau levels and the Fermi surface. The decrease of the MC at low
magnetic field is caused by the exchange interaction between the electron
in the conduction band and the magnetic ions.Comment: 6 pages, 9 figures, submitted to Phys. Rev.
Oscillating magnetoresistance in diluted magnetic semiconductor barrier structures
Ballistic spin polarized transport through diluted magnetic semiconductor
(DMS) single and double barrier structures is investigated theoretically using
a two-component model. The tunneling magnetoresistance (TMR) of the system
exhibits oscillating behavior when the magnetic field are varied. An
interesting beat pattern in the TMR and spin polarization is found for
different NMS/DMS double barrier structures which arises from an interplay
between the spin-up and spin-down electron channels which are splitted by the
s-d exchange interaction.Comment: 4 pages, 6 figures, submitted to Phys. Rev.
Vortices in Schwinger-Boson Mean-Field Theory of Two-Dimensional Quantum Antiferromagnets
In this paper we study the properties of vortices in two dimensional quantum
antiferromagnets with spin magnitude S on a square lattice within the framework
of Schwinger-boson mean field theory. Based on a continuum description, we show
that vortices are stable topological excitations in the disordered state of
quantum antiferromagnets. Furthermore, we argue that vortices can be divided
into two kinds: the first kind always carries zero angular momentum and are
bosons, whereas the second kind carries angular momentum S under favourable
conditions and are fermions if S is half-integer. A plausible consequence of
our results relating to RVB theories of High-Tc superconductors is pointed out.Comment: 25 page
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