3,751 research outputs found
Steady-state traffic flow on a ring road with up- and down- slopes
This paper studies steady-state traffic flow on a ring road with up- and
down- slopes using a semi-discrete model. By exploiting the relations between
the semi-discrete and the continuum models, a steady-state solution is uniquely
determined for a given total number of vehicles on the ring road. The solution
is exact and always stable with respect to the first-order continuum model,
whereas it is a good approximation with respect to the semi-discrete model
provided that the involved equilibrium constant states are linearly stable. In
an otherwise case, the instability of one or more equilibria could trigger
stop-and-go waves propagating in certain road sections or throughout the ring
road. The indicated results are reasonable and thus physically significant for
a better understanding of real traffic flow on an inhomogeneous road
Assessing Learning-Centered Leadership: Connections to Research, Professional Standards, and Current Practices
Describes an assessment model designed to evaluate school leaders' performance. Unlike existing tools, this new system will assess both individuals and teams, and focuses specifically on instructional leadership and behaviors that improve learning
A Coupled AKNS-Kaup-Newell Soliton Hierarchy
A coupled AKNS-Kaup-Newell hierarchy of systems of soliton equations is
proposed in terms of hereditary symmetry operators resulted from Hamiltonian
pairs. Zero curvature representations and tri-Hamiltonian structures are
established for all coupled AKNS-Kaup-Newell systems in the hierarchy.
Therefore all systems have infinitely many commuting symmetries and
conservation laws. Two reductions of the systems lead to the AKNS hierarchy and
the Kaup-Newell hierarchy, and thus those two soliton hierarchies also possess
tri-Hamiltonian structures.Comment: 15 pages, late
Observation of Fermi-energy dependent unitary impurity resonances in a strong topological insulator Bi_2Se_3 with scanning tunneling spectroscopy
Scanning tunneling spectroscopic studies of Bi_2Se_3 epitaxial films on Si (111) substrates reveal highly localized unitary impurity resonances associated with non-magnetic quantum impurities. The strength of the resonances depends on the energy difference between the Fermi level (E_F) and the Dirac point (E_D) and diverges as E_F approaches E_D. The Dirac-cone surface state of the host recovers within ~ 2Ã… spatial distance from impurities, suggesting robust topological protection of the surface state of topological insulators against high-density impurities that preserve time reversal symmetry
Study on the design schemes of marine warning and forecasting system platform
The system platform of marine monitoring and disaster forecasting plays an important role in ocean observations, data collection as well as disaster prevention and mitigation. This paper discusses the necessity and significance of the system platform construction in Jiangsu Province, China. We take the construction of the observation platform as an example, considering the difficulties of the project design, analyzed the influence factors like wind, water level, tide, wave, earthquake and corrosion. On the basis, we study the platform???s program layout, hydraulic structures scheme, layout of main observation devices, power supply and lightning, construction scheme. The research results can provide a reference for the design of the subsequent ocean observing platform, and can be further applied in other related design of observation platform
Exact one-periodic and two-periodic wave solutions to Hirota bilinear equations in 2+1 dimensions
Riemann theta functions are used to construct one-periodic and two-periodic
wave solutions to a class of (2+1)-dimensional Hirota bilinear equations. The
basis for the involved solution analysis is the Hirota bilinear formulation,
and the particular dependence of the equations on independent variables
guarantees the existence of one-periodic and two-periodic wave solutions
involving an arbitrary purely imaginary Riemann matrix. The resulting theory is
applied to two nonlinear equations possessing Hirota bilinear forms:
and
where , thereby yielding their one-periodic and two-periodic wave
solutions describing one dimensional propagation of waves
Speed and spin differences between the old celluloid versus new plastic table tennis balls and the effect on the kinematic responses of elite versus sub-elite players
This study measured 1) the speed and spin differences between the old celluloid versus new plastic table tennis balls at pre ball-table impact and post ball-table impact when projected with topspin at 7.56 m.s-1, and investigated 2) the effect this has on the kinematic responses of 5 elite versus 5 sub-elite players’ forehand topspin in response to topspin and backspin. Plastic balls were lower in both speed and spin at pre and post ball-table impact compared with celluloid balls but the magnitude of change in speed and spin for each ball material differed. During flight before impact, plastic balls lost 3.98% more speed and 1.24% more spin than celluloid balls. Post ball-table impact, plastic balls showed a greater speed increment (0.69%) and smaller spin decrement (0.19%) than celluloid balls. Differences in players’ kinematic responses to the different ball materials were found only when players returned backspin shots. Players supinated their rackets more by 2.23% at ball-racket contact and produced 3.37% less ball spin when returning plastic compared with celluloid balls; an indication of an early adaptation to the lower spin rate of plastic balls. The lack of differences in kinematic response to topspin may be due to the similar changes in speed and spin of both types of balls at ball-table impact. It is not known if a higher initial ball projection velocity would evoke differences in movement responses from the players post ball-table impact but could be explored in future studies
Engineering Ratchet-Based Particle Separation via Shortcuts to Isothermality
Microscopic particle separation plays vital role in various scientific and
industrial domains. In this Letter, we propose a universal non-equilibrium
thermodynamic approach, employing the concept of Shortcuts to Isothermality, to
realize controllable separation of overdamped Brownian particles. By utilizing
a designed ratchet potential with temporal period , we find in the
slow-driving regime that the average particle velocity
\Bar{v}_s\propto\left(1-D/D^*\right)\tau^{-1}, indicating that particles with
different diffusion coefficients can be guided to move in distinct
directions with a preset . Furthermore, we reveal that there exists an
extra energetic cost with a lower bound
W_{\rm{ex}}^{(\rm{min})}\propto\mathcal{L}^{2}\Bar{v}_s, alongside a
quasi-static work consumption. Here, is the thermodynamic length
of the driving loop in the parametric space. We numerically validate our
theoretical findings and illustrate the optimal separation protocol (associated
with ) with a sawtooth potential. This study
establishes a bridge between thermodynamic process engineering and particle
separation, paving the way for further explorations of thermodynamic constrains
and optimal control in ratchet-based particle separation.Comment: 5 pages, 3 figures + Supplemental Materials (10 pages, 4 figures).
Comments are welcome
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