99 research outputs found
Perception of Waiting Time at Signalized Intersections
Perceived waiting time at signalized intersections differs from the real value, and varies with signal design. The onerousness of delay depends on the conditions under which it is experienced. Using weighted travel time time may contribute to optimal signal control if its use can improve upon assuming that all time is weighted equally by users. This research explores the perception of waiting time at signalized intersections based on the results of an online survey, which directly collected the perceived waiting time and the user ratings of the signal designs of each intersection on an arterial including 3 intersections. Statistically analyzing the survey data suggests the perception of waiting time is a function of the real time; and a quadratic model better can describes relationship. The survey also indicates that there exists a tradeoff between the total waiting time and the individual waiting time of each intersection. It turns out that drivers prefer to split the total waiting time at different intersections at the price of a longer total wait if the difference of the total waiting time of two signal designs is within 30 seconds. The survey data shows that the perceived waiting time, instead of the real waiting time, better explains how users will rate the individual signal designs for both intersections and arterials including multiple intersections.Traffic Signal, Stated Preference, Virtual Experience Stated Preference, Signalized Intersection, Value of Time, Perception of Time
Topological Disorder Operators in Three-Dimensional Conformal Field Theory
Many abelian gauge theories in three dimensions flow to interacting conformal
field theories in the infrared. We define a new class of local operators in
these conformal field theories which are not polynomial in the fundamental
fields and create topological disorder. They can be regarded as
higher-dimensional analogues of twist and winding-state operators in free 2d
CFTs. We call them monopole operators for reasons explained in the text. The
importance of monopole operators is that in the Higgs phase, they create
Abrikosov-Nielsen-Olesen vortices. We study properties of these operators in
three-dimensional QED using large N_f expansion. In particular, we show that
monopole operators belong to representations of the conformal group whose
primaries have dimension of order N_f. We also show that monopole operators
transform non-trivially under the flavor symmetry group, with the precise
representation depending on the value of the Chern-Simons coupling.Comment: 24 pages, latex. v2: a reference to prior work has been adde
Enhanced heat capacity and a new temperature instability in superfluid He-4 in the presence of a constant heat flux near T-lambda
We present the first experimental evidence that the heat capacity of superfluid 4He, at temperatures very close to the lambda point Tλ, is enhanced by a constant heat flux Q. The heat capacity at constant Q, CQ, is predicted to diverge at a temperature Tc(Q)<Tλ at which superflow becomes unstable. In agreement with previous measurements, we find that dissipation enters our cell at a temperature, TDAS(Q), below the theoretical value, Tc(Q). We argue that TDAS(Q) can be accounted for by a temperature instability at the cell wall, and is therefore distinct from Tc(Q). The excess heat capacity we measure has the predicted scaling behavior as a function of T and Q, but it is much larger than predicted by current theory
Monopole operators and mirror symmetry in three dimensions
We study vortex-creating, or monopole, operators in 3d CFTs which are the infrared limit of N = 2 and N = 4 supersymmetric QEDs in three dimensions. Using large-N-f expansion, we construct monopole operators which are primaries of short representations of the superconformal algebra. Mirror symmetry in three dimensions makes a number of predictions about such operators, and our results confirm these predictions. Furthermore, we argue that some of our large-N-f results are exact. This implies, in particular, that certain monopole operators in N = 4 d = 3 SQED with N-f = 1 are free fields. This amounts to a proof of 3d mirror symmetry in a special case
An Empirical Analysis on the Arterial Fundamental Diagram
For uninterrupted traffic flow, it is well-known that the fundamental diagram (FD) describes the relationship between traffic flow and density under steady state. For interrupted traffic flow on a signalized road, it has been recognized that the arterial fundamental diagram (AFD) is significantly affected by signal operations. But little research up to date has discussed in detail how signal operations impact the AFD. In this paper, based upon empirical observations from high-resolution event-based traffic signal data collected from a major arterial in the Twin Cities area, we study the impacts of g/C ratio, signal coordination, and turning movements on the cycle-based AFD, which describes the relationship between traffic flow and occupancy in a signal cycle. By microscopically investigating individual vehicle trajectories from event-based data, we demonstrate that not only g/C ratio constrains the capacity of a signalized approach, poor signal coordination and turning movements from upstream intersections also have significant impact on the capacity. We show that an arterial link may not be congested even with high occupancy values. Such high values could result from queue build-up during red light that occupies the detector, i.e. the Queue-Over-Detector (QOD) phenomenon discussed in this paper. More importantly, by removing the impact of QOD, a stable form of AFD is revealed, and one can use that to identify three different regimes including under-saturation, saturation, and over-saturation with queue spillovers. We believe the stable form of AFD is of great importance for traffic signal control because of its ability to identify traffic states on a signal link. (C) 2010 Elsevier Ltd. All rights reserved
Branes wrapping Black Holes
We examine the dynamics of extended branes, carrying lower dimensional brane
charges, wrapping black holes and black hole microstates in M and Type II
string theory. We show that they have a universal dispersion relation typical
of threshold bound states with a total energy equal to the sum of the
contributions from the charges. In near-horizon geometries of black holes,
these are BPS states, and the dispersion relation follows from supersymmetry as
well as properties of the conformal algebra. However they break all
supersymmetries of the full asymptotic geometries of black holes and
microstates. We comment on a recent proposal which uses these states to explain
black hole entropy.Comment: 41 pages, 2 figures;v2: references adde
Quantizing String Theory in AdS_5 X S^5: Beyond the pp-Wave
In a certain kinematic limit, where the effects of spacetime curvature (and
other background fields) greatly simplify, the light-cone gauge world-sheet
action for a type IIB superstring on AdS_5 x S^5 reduces to that of a free
field theory. It has been conjectured by Berenstein, Maldacena, and Nastase
that the energy spectrum of this string theory matches the dimensions of
operators in the appropriately defined large R-charge large-N_c sector of N=4
supersymmetric Yang--Mills theory in four dimensions. This holographic
equivalence is thought to be exact, independent of any simplifying kinematic
limits. As a step toward verifying this larger conjecture, we have computed the
complete set of first curvature corrections to the spectrum of light-cone gauge
string theory that arises in the expansion of AdS_5 x S^5 about the plane-wave
limit. The resulting spectrum has the complete dependence on lambda = g_YM^2
N_c; corresponding results in the gauge theory are known only to second order
in lambda. We find precise agreement to this order, including the N=4 extended
supermultiplet structure. In the process, we demonstrate that the complicated
schemes put forward in recent years for defining the Green--Schwarz superstring
action in background Ramond-Ramond fields can be reduced to a practical (and
correct) method for quantizing the string.Comment: 39 pages; substantial improvement
ChIP-Hub provides an integrative platform for exploring plant regulome
Plant genomes encode a complex and evolutionary diverse regulatory grammar that forms the basis for most life on earth. A wealth of regulome and epigenome data have been generated in various plant species, but no common, standardized resource is available so far for biologists. Here, we present ChIP-Hub, an integrative web-based platform in the ENCODE standards that bundles >10,000 publicly available datasets reanalyzed from >40 plant species, allowing visualization and meta-analysis. We manually curate the datasets through assessing ~540 original publications and comprehensively evaluate their data quality. As a proof of concept, we extensively survey the co-association of different regulators and construct a hierarchical regulatory network under a broad developmental context. Furthermore, we show how our annotation allows to investigate the dynamic activity of tissue-specific regulatory elements (promoters and enhancers) and their underlying sequence grammar. Finally, we analyze the function and conservation of tissue-specific promoters, enhancers and chromatin states using comparative genomics approaches. Taken together, the ChIP-Hub platform and the analysis results provide rich resources for deep exploration of plant ENCODE. ChIP-Hub is available at https://biobigdata.nju.edu.cn/ChIPHub/.Peer Reviewe
- âŠ