130 research outputs found
Queue replacement principle for corridor problems with heterogeneous commuters
This study investigates the theoretical properties of a departure time choice
problem considering commuters' heterogeneity with respect to the value of
schedule delay in corridor networks. Specifically, we develop an analytical
method to solve the dynamic system optimal (DSO) and dynamic user equilibrium
(DUE) problems. To derive the DSO solution, we first demonstrate the
bottleneck-based decomposition property, i.e., the DSO problem can be
decomposed into multiple single bottleneck problems. Subsequently, we obtain
the analytical solution by applying the theory of optimal transport to each
decomposed problem and derive optimal congestion prices to achieve the DSO
state. To derive the DUE solution, we prove the queue replacement principle
(QRP) that the time-varying optimal congestion prices are equal to the queueing
delay in the DUE state at every bottleneck. This principle enables us to derive
a closed-form DUE solution based on the DSO solution. Moreover, as an
application of the QRP, we prove that the equilibrium solution under various
policies (e.g., on-ramp metering, on-ramp pricing, and its partial
implementation) can be obtained analytically. Finally, we compare these
equilibria with the DSO state.Comment: 36 pages, 15 figure
Global stability of day-to-day dynamics for schedule-based Markovian transit assignment with boarding queues
Schedule-based transit assignment describes congestion in public transport
services by modeling the interactions of passenger behavior in a time-space
network built directly on a transit schedule. This study investigates the
theoretical properties of scheduled-based Markovian transit assignment with
boarding queues. When queues exist at a station, passenger boarding flows are
loaded according to the residual vehicle capacity, which depends on the flows
of passengers already on board with priority. An equilibrium problem is
formulated under this nonseparable link cost structure as well as explicit
capacity constraints. The network generalized extreme value (NGEV) model, a
general class of additive random utility models with closed-form expression, is
used to describe the path choice behavior of passengers. A set of formulations
for the equilibrium problem is presented, including variational inequality and
fixed-point problems, from which the day-to-day dynamics of passenger flows and
costs are derived. It is shown that Lyapunov functions associated with the
dynamics can be obtained and guarantee the desirable solution properties of
existence, uniqueness, and global stability of the equilibria. In terms of
dealing with stochastic equilibrium with explicit capacity constraints and
non-separable link cost functions, the present theoretical analysis is a
generalization of the existing day-to-day dynamics in the context of general
traffic assignment.Comment: 26 pages, 3 figure
Pressure-Induced Antiferromagnetic Bulk Superconductor EuFeAs
We present the magnetic and superconducting phase diagram of EuFeAs
for and . The antiferromagnetic phase of the
Eu moments is completely enclosed in the superconducting phase. The
upper critical field vs. temperature curves exhibit strong concave curvatures,
which can be explained by the Jaccarino-Peter compensation effect due to the
antiferromagnetic exchange interaction between the Eu moments and
conduction electrons.Comment: submitted to the proceedings of the M2S-IX Toky
Cyclotron resonance and mass enhancement by electron correlation in KFeAs
Cyclotron resonance (CR) measurements for the Fe-based superconductor
KFeAs are performed. One signal for CR is observed, and is attributed
to the two-dimensional Fermi surface at the point. We found a
large discrepancy in the effective masses of CR [(3.40.05) ( is
the free electron mass)] and de-Haas van Alphen (dHvA) results, a direct
evidence of mass enhancement due to electronic correlation. A comparison of the
CR and dHvA results shows that both intra- and interband electronic
correlations contribute to the mass enhancement in KFeAs.Comment: 5 pages, 4 figure
Quasi-Two-Dimensional Fermi Surfaces and Coherent Interlayer Transport in KFeAs
We report the results of the angular-dependent magnetoresistance oscillations
(AMROs), which can determine the shape of bulk Fermi surfaces in
quasi-two-dimensional (Q2D) systems, in a highly hole-doped Fe-based
superconductor KFeAs with 3.7 K. From the AMROs, we
determined the two Q2D FSs with rounded-square cross sections, corresponding to
12% and 17% of the first Brillouin zone. The rounded-squared shape of the FS
cross section is also confirmed by the analyses of the interlayer transport
under in-plane fields. From the obtained FS shape, we infer the character of
the 3d orbitals that contribute to the FSs.Comment: 4 pages, 4 figures, accepted in Phys. Rev. Let
Stochastic stability of dynamic user equilibrium in unidirectional networks: Weakly acyclic game approach
The aim of this study is to analyze the stability of dynamic user equilibrium (DUE) with fixed departure times in unidirectional networks. Specifically, stochastic stability, which is the concept of stability in evolutionary dynamics subjected to stochastic effects, is herein considered. To achieve this, a new approach is developed by synthesizing the three concepts: the decomposition technique of DUE assignments, the weakly acyclic game, and the asymptotic analysis of the stationary distribution of perturbed dynamics. Specifically, we first formulate a DUE assignment as a strategic game (DUE game) that deals with atomic users. We then prove that there exists an appropriate order of assigning users for ensuring equilibrium in a unidirectional network. With this property, we establish the relationship between DUE games in unidirectional networks and weakly acyclic games. The convergence and stochastic stability of better response dynamics in the DUE games are then proved based on the theory of weakly acyclic games. Finally, we observe the properties of the convergence and stability from numerical experiments. The results show that the strict improvement of users’ travel times by the applied evolutionary dynamics is important for ensuring the existence of a stochastically stable equilibrium in DUE games
Integer spin-chain antiferromagnetism of the 4d oxide CaRuO3 with post-perovskite structure
A quasi-one dimensional magnetism was discovered in the post-perovskite
CaRuO3 (Ru4+: 4d4, Cmcm), which is iso-compositional with the perovskite CaRuO3
(Pbnm). An antiferromagnetic spin-chain function with -J/kB = 350 K well
reproduces the experimental curve of the magnetic susceptibility vs.
temperature, suggesting long-range antiferromagnetic correlations. The
anisotropic magnetism is probably owing to the dyz - 2p- dzx and dzx - 2p- dyz
superexchange bonds along a-axis. The Sommerfeld coefficient of the specific
heat is fairly small, 0.16(2) mJ mol-1 K-2, indicating that the magnetism
reflects localized nature of the 4d electrons. As far as we know, this is the
first observation of an integer (S = 1) spin-chain antiferromagnetism in the 4d
electron system.Comment: Accepted for publication in Phys. Rev.
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