1,924 research outputs found
Hamiltonian structure of Hamiltonian chaos
From a kinematical point of view, the geometrical information of hamiltonian
chaos is given by the (un)stable directions, while the dynamical information is
given by the Lyapunov exponents. The finite time Lyapunov exponents are of
particular importance in physics. The spatial variations of the finite time
Lyapunov exponent and its associated (un)stable direction are related. Both of
them are found to be determined by a new hamiltonian of same number of degrees
of freedom as the original one. This new hamiltonian defines a flow field with
characteristically chaotic trajectories. The direction and the magnitude of the
phase flow field give the (un)stable direction and the finite time Lyapunov
exponent of the original hamiltonian. Our analysis was based on a
degree of freedom hamiltonian system
A Strategic Approach Using Representative LV Networks in the Assessment of Technical Losses on LV Network with Solar Photovoltaic
Low voltage network (LVN) forms an extensive part of the distribution network as it is used to connect electricity supply from utility substations to diverse segments of loads in different geographic locations. With the increasingly high penetration of solar PV in LVN, utility companies are finding it necessary to establish the contribution of these solar PV to the overall technical losses in the distribution network. This paper presents a strategic approach using representative LVN to determine the impact of solar PV on technical losses on the LVN. Five types of representative LVN characterized by different customer load segments (domestic, commercial and industrial) and peak load demand were developed. The impact on technical losses of solar PV connected to these representatives LVN were assessed on a statistical basis for a supply zone. The results obtained are consistent and could be applied to establish investment strategies on distribution network, tariff revision exercise and optimization of distribution network planning/design
Transport spectroscopy in a time-modulated open quantum dot
We have investigated the time-modulated coherent quantum transport phenomena
in a ballistic open quantum dot. The conductance and the electron dwell
time in the dots are calculated by a time-dependent mode-matching method. Under
high-frequency modulation, the traversing electrons are found to exhibit three
types of resonant scatterings. They are intersideband scatterings: into
quasibound states in the dots, into true bound states in the dots, and into
quasibound states just beneath the subband threshold in the leads. Dip
structures or fano structures in are their signatures. Our results show
structures due to 2 intersideband processes. At the above
scattering resonances, we have estimated, according to our dwell time
calculation, the number of round-trip scatterings that the traversing electrons
undertake between the two dot openings.Comment: 8 pages, 5 figure
Determining the unsaturated hydraulic conductivity of a compacted sand-bentonite mixture under constant volume and free-swell conditions
Highly compacted sand-bentonite mixtures are often considered as possible
engineered barriers in deep high-level radioactive waste disposals. In-situ,
the saturation of these barriers from their initially unsaturated state is a
complex hydro-mechanical coupled process in which temperature effects also play
a role. The key parameter of this process is the unsaturated hydraulic
conductivity of the barrier. In this paper, isothermal infiltration experiments
were conducted to determine the unsaturated hydraulic conductivity according to
the instantaneous profile method. To do so, total suction changes were
monitored at different locations along the soil specimen by using resistivity
relative humidity probes. Three constant volume infiltration tests were
conducted showing, unexpectedly, a decrease of the hydraulic conductivity
during infiltration. One test performed under free-swell conditions showed the
opposite and standard trend. These observations were interpreted in terms of
microstructure changes during wetting, both under constant volume and free
swell conditions
Asymptotic normalization coefficients for 8B->7Be+p from a study of 8Li->7Li+n
Asymptotic normalization coefficients (ANCs) for 8Li->7Li+n have been
extracted from the neutron transfer reaction 13C(7Li,8Li)12C at 63 MeV. These
are related to the ANCs in 8B->7Be+p using charge symmetry. We extract ANCs for
8B that are in very good agreement with those inferred from proton transfer and
breakup experiments. We have also separated the contributions from the p_1/2
and p_3/2 components in the transfer. We find the astrophysical factor for the
7Be(p,gamma)8B reaction to be S_17(0)=17.6+/-1.7 eVb. This is the first time
that the rate of a direct capture reaction of astrophysical interest has been
determined through a measurement of the ANCs in the mirror system.Comment: 5 pages, 3 figures, 2 table
From double Lie groupoids to local Lie 2-groupoids
We apply the bar construction to the nerve of a double Lie groupoid to obtain
a local Lie 2-groupoid. As an application, we recover Haefliger's fundamental
groupoid from the fundamental double groupoid of a Lie groupoid. In the case of
a symplectic double groupoid, we study the induced closed 2-form on the
associated local Lie 2-groupoid, which leads us to propose a definition of a
symplectic 2-groupoid.Comment: 23 pages, a few minor changes, including a correction to Lemma 6.
A low-voltage retarding-field Mott polarimeter for photocathode characterization
Nuclear physics experiments at Thomas Jefferson National Accelerator
Facility's CEBAF rely on high polarization electron beams. We describe a
recently commissioned system for prequalifying and studying photocathodes for
CEBAF with a load-locked, low-voltage polarized electron source coupled to a
compact retarding-field Mott polarimeter. The polarimeter uses simplified
electrode structures and operates from 5 to 30 kV. The effective Sherman
function for this device has been calibrated by comparison with the CEBAF 5 MeV
Mott polarimeter. For elastic scattering from a thick gold target at 20 keV,
the effective Sherman function is 0.201(5). Its maximum efficiency at 20 keV,
defined as the detected count rate divided by the incident particle current, is
5.4(2) x 10-4, yielding a figure-of-merit, or analyzing power squared times
efficiency, of 1.0(1) x 10-5. The operating parameters of this new polarimeter
design are compared to previously published data for other compact Mott
polarimeters of the retarding-field type.Comment: 9 figure
The importance of self-consistency in determining interface properties of S-I-N and D-I-N structures
We develop a method to solve the Bogoliubov de Gennes equation for
superconductors self-consistently, using the recursion method. The method
allows the pairing interaction to be either local or non-local corresponding to
and --wave superconductivity, respectively. Using this method we examine
the properties of various and interfaces. In particular we
self-consistently calculate the spatially varying density of states and the
superconducting order parameter. We see that changing the strength of the
insulating barrier, at the interface, does not, in the case of an --wave
superconductor, dramatically, change the low energy local density of states, in
the superconducting region near the interface. This is in stark contrast to
what we see in the case of a interface where the local particle density
of states is changed dramatically. Hence we deduce that in calculating such
properties as the conductance of and structures it is far more
important to carry out a self-consistent calculations in the --wave case.Comment: 14 pages, 8 figures, submitted to special issue of "Superlattices and
Microstructures
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