23,304 research outputs found
Boundary States in Graphene Heterojunctions
A new type of states in graphene-based planar heterojunctions has been
studied in the envelope wave function approximation. The condition for the
formation of these states is the intersection between the dispersion curves of
graphene and its gap modification. This type of states can also occur in smooth
graphene-based heterojunctions.Comment: 5 pages, 3 figure
Partial Regularity of solutions to the Four-dimensional Navier-Stokes equations at the first blow-up time
The solutions of incompressible Navier-Stokes equations in four spatial
dimensions are considered. We prove that the two-dimensional Hausdorff measure
of the set of singular points at the first blow-up time is equal to zero.Comment: 19 pages, a comment regarding five or higher dimensional case is
added in Remark 1.3. accepted by Comm. Math. Phy
Conceptual aspects of QCD factorization in hadronic B decays
I review the meaning of ``QCD factorization'' in hadronic two-body B decays
and then discuss recent results of theoretical (rather than phenomenological)
nature: the proof of factorization at two loops; the identification of
``chirally enhanced'' power corrections; and the role of annihilation
contributions.Comment: 10 pages, LaTeX. Based on talks presented at the UK Phenomenology
Workshop on Heavy Flavour and CP Violation, 17 - 22 September 2000, Durham,
proceedings to appear in J. Phys. G; the 5th International Symposium on
Radiative Corrections (RADCOR2000), Carmel, California, September 11 - 15,
2000; the 4th Workshop on Continuous Advances in QCD, Minneapolis, 12-14 May
2000; the Vth International Workshop on Heavy Quark Physics, Dubna, 6-8 April
200
A review of the six-minute walk test: Its implication as a self-administered assessment tool
Promoting self-management and monitoring physical activity are important strategies in chronic heart disease (CHD) management. The six-minute walk test (6MWT) is a commonly used sub-maximal exercise test for measuring physical functional capacity. The aim of this paper is to review the current literature on 6MWT relating to methodological issues as well as exploring the potential of the protocol to be adopted as a self-administered exercise test. The Medline, CINAHL, Science Direct and the World Wide Web using the search engine Google, were searched for articles describing the administration, reliability and validity of the 6MWT. Findings of the integrative literature review the 6MWT is a simple, safe tool. To date, the capacity for self-administration of the 6MWT has not been investigated. Adapting the 6MWT as a patient-reported outcome measure may enhance the capacity, not only for clinicians to monitor functional status, but also promote self-management by enabling individuals to monitor changes in their functional capacity
QCD factorization for B -> PP
In this work, we give a detailed discussion for QCD factorization involved
the complete chirally enhanced power corrections for B decays to two light
pseudoscalar mesons, and present some detailed calculations of radiative
corrections at the order of alpha_s. We point out that the infrared finiteness
of the vertex corrections in the chirally enhanced power corrections requires
twist-3 light-cone distribution amplitudes (LCDAs) of the light pseudoscalar
symmetric. However, even in the symmetric condition, there is also logarithmic
divergence from the endpoints of the twist-3 LCDAs in the hard spectator
scattering. We point out that the decay amplitudes of B --> PP predicted by QCD
factorization are really free of the renormalization scale dependence, at least
at the order of alpha_s. At last, we briefly compare the QCD factorization with
the generalized factorization and PQCD method.Comment: 31 pages, 3 eps figure
Signatures of Electronic Nematic Phase at Isotropic-Nematic Phase Transition
The electronic nematic phase occurs when the point-group symmetry of the
lattice structure is broken, due to electron-electron interactions. We study a
model for the nematic phase on a square lattice with emphasis on the phase
transition between isotropic and nematic phases within mean field theory. We
find the transition to be first order, with dramatic changes in the Fermi
surface topology accompanying the transition. Furthermore, we study the
conductivity tensor and Hall constant as probes of the nematic phase and its
transition. The relevance of our findings to Hall resistivity experiments in
the high- cuprates is discussed.Comment: 5 pages, 3 figure
Analytical model for large-scale design of sidewalk delivery robot systems
With the rise in demand for local deliveries and e-commerce, robotic
deliveries are being considered as efficient and sustainable solutions.
However, the deployment of such systems can be highly complex due to numerous
factors involving stochastic demand, stochastic charging and maintenance needs,
complex routing, etc. We propose a model that uses continuous approximation
methods for evaluating service trade-offs that consider the unique
characteristics of large-scale sidewalk delivery robot systems used to serve
online food deliveries. The model captures both the initial cost and the
operation cost of the delivery system and evaluates the impact of constraints
and operation strategies on the deployment. By minimizing the system cost,
variables related to the system design can be determined. First, the
minimization problem is formulated based on a homogeneous area, and the optimal
system cost can be derived as a closed-form expression. By evaluating the
expression, relationships between variables and the system cost can be directly
obtained. We then apply the model in neighborhoods in New York City to evaluate
the cost of deploying the sidewalk delivery robot system in a real-world
scenario. The results shed light on the potential of deploying such a system in
the future
- …