34,127 research outputs found
On the Treatment of Repeated Observations in Panel Data: Efficiency of Mixed Logit Parameter Estimates
No full textPanel data with repeated observations, Discrete choice models, Parameter efficiency,
Video vehicle detection at signalised junctions: a simulation-based study
No full textMany existing advanced methods of traffic signal control depend on information about
approaching traffic provided by inductive loop detectors at particular points in the road. But
analysis of images from CCTV cameras can in principle provide more comprehensive
information about traffic approaching and passing through junctions, and cameras may be
easier to install and maintain than loop detectors, and some systems based on video detection
have already been in use for some time.
Against this background, computer simulation has been used to explore the potential of
existing and immediately foreseeable capability in automatic on-line image analysis to extract
information relevant to signal control from images provided by cameras mounted in
acceptable positions at signal-controlled junctions. Some consequences of extracting relevant
information in different ways were investigated in the context of an existing detailed
simulation model of vehicular traffic moving through junctions under traffic-responsive signal
control, and the development of one basic and one advanced algorithm for traffic-responsive
control. The work was confined as a first step to operation of one very simple signalcontrolled
junction.
Two techniques for extraction of information from images were modelled - a more ambitious
technique based on distinguishing most of the individual vehicles visible to the camera, and a
more modest technique requiring only that the presence of vehicles in any part of the image
be distinguished from the background scene. In the latter case, statistical modelling was used
to estimate the number of vehicles corresponding to any single area of the image that
represents vehicles rather than background.
At the simple modelled junction, each technique of extraction enabled each of the algorithms
for traffic-responsive control of the signals to achieve average delays per vehicle appreciably
lower than those given by System D control, and possibly competitive with those that MOVA
would give, but comparison with MOVA was beyond the scope of the initial study.
These results of simulation indicate that image analysis of CCTV pictures should be able to
provide sufficient information in practice for traffic-responsive control that is competitive
with existing techniques. Ways in which the work could be taken further were discussed with
practitioners, but have not yet been progressed
On the treatment of the repeated observations in panel data: efficiency of Mixed Logit parameter estimates
No full textDispelling the Myths Behind First-author Citation Counts
No full textWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
System optimal traffic assignment with departure time choice
No full textThis thesis investigates analytical dynamic system optimal assignment with departure time
choice in a rigorous and original way. Dynamic system optimal assignment is formulated here
as a state-dependent optimal control problem. A fixed volume of traffic is assigned to
departure times and routes such that the total system travel cost is minimized. Although the
system optimal assignment is not a realistic representation of traffic, it provides a bound on
performance and shows how the transport planner or engineer can make the best use of the
road system, and as such it is a useful benchmark for evaluating various transport policy
measures. The analysis shows that to operate the transport system optimally, each traveller in
the system should consider the dynamic externality that he or she imposes on the system from
the time of his or her entry. To capture this dynamic externality, we develop a novel
sensitivity analysis of travel cost. Solution algorithms are developed to calculate the dynamic
externality and traffic assignments based on the analyses. We also investigate alternative
solution strategies and the effect of time discretization on the quality of calculated
assignments. Numerical examples are given and the characteristics of the results are discussed.
Calculating dynamic system optimal assignment and the associated optimal toll could be too
difficult for practical implementation. We therefore consider some practical tolling strategies
for dynamic management of network traffic. The tolling strategies considered in this thesis
include both uniform and congestion-based tolling strategies, which are compared with the
dynamic system optimal toll so that their performance can be evaluated. In deriving the
tolling strategies, it is assumed that we have an exact model for the underlying traffic
behaviour. In reality, we do not have such information so that the robustness of a toll
calculation method is an important issue to be investigated in practice. It is found that the
tolls calculated by using divided linear traffic models can perform well over a wide range of
scenarios. The divided linear travel time models thus should receive more attention in the
future research on robust dynamic traffic control strategies design. In conclusion, this thesis
contributes to the literature on dynamic traffic modelling and management, and to support
further analysis and model development in this area
THE TRANSITION OF MOLECULAR OXYGEN
No full textAuthor Institution: Research School of Physical Sciences and Engineering, The Australian National University; Molecular Physics Laboratory, SRI InternationalThe origin of the intensity of the transition of molecular oxygen, first observed recently by Eppink et al. [J. Chem. Phys. 108, 1305 (1998).], is discussed. It is shown that the transition borrows its intensity principally from the dipole-allowed transition, through spin-orbit mixing between the and states. Estimated continuum photoabsorption cross sections and discrete oscillator strengths for the system are presented
Observations of Bºs→ψ(2S)η and Bº(s)→ψ(2S)π+π- decays
No full textFirst observations of the B0s
→ψ(2S)η, B0 →ψ(2S)π
+
π
− and B0s
→ψ(2S)π
+
π
− decays are made
using a dataset corresponding to an integrated luminosity of 1.0 fb−1 collected by the LHCb experiment in
proton–proton collisions at a centre-of-mass energy of
√
s = 7 TeV. The ratios of the branching fractions
of each of the ψ(2S) modes with respect to the corresponding J/ψ decays are
B(B0s
→ψ(2S)η)
÷
B(B0s
→J/ψη)
= 0.83± 0.14 (stat)±0.12 (syst) ±0.02 (B),
;
B(B0→ψ(2S)π
+
π
−
)
÷
B(B0→J/ψπ
+
π
−
)
= 0.56± 0.07 (stat)±0.05 (syst)± 0.01 (B),
;
B(B0s
→ψ(2S)π
+
π
−
)
÷
B(B0s
→J/ψπ
+
π
−
)
= 0.34± 0.04 (stat)±0.03 (syst)± 0.01 (B),
where the third uncertainty corresponds to the uncertainties of the dilepton branching fractions of the J/ψ
and ψ(2S) meson decays
The Grothendieck-Cousin complex on G/B x G/B
No full textIn his 1978 paper, The Grothendieck-Cousin complex of an induced representation, G. Kempf computes the Cousin complex corresponding to an induced representation of a reductive algebraic group G. His technique uses the geometry of the homogeneous space G/B, B being a Borel subgroup of G. The complex gives a resolution by B-modules, which easily yields the Weyl character formula.Instead of considering G/B, we analyze the analagous situation for . The Cousin complex corresponding to an induced representation in this case consists of G-modules. We are able to study the terms of the complex by exploiting parallels between the B-action on G/B and the G-action on --there is a natural one-to-one correspondence between the orbits of these actions. Our work here is greatly simplified by reducing to the affine situation and applying the theory of A-G modules. We construct a spectral sequence relating the terms of the complexes. Finally, an application to the theory of D-modules is given.Made available in DSpace on 2011-05-07T12:16:39Z (GMT). No. of bitstreams: 2
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G (A, B)-labeling of cacti over groups
No full text© 2016 Author(s). Let G be a group with nonempty subsets A and B. The graph G(A, B) is the simple graph obtained by deleting all loops from the graph whose vertex set is A and where vertices x and y are adjacent if and only if there is a b B such that xb = y or yb = x. In this paper, we present realizations of some cacti as G(A, B)\u27s
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