4,299 research outputs found
A Threshold Model of Real US GDP and the Problem of Constructing Confidence Intervals in TAR Models
We estimate real U.S. GDP growth as a threshold autoregressive process, and construct confidence intervals for the parameter estimates. However, there are various approaches that can be used in constructing the confidence intervals. Specifically, standard- t , bootstrap- t , and bootstrap-percentile confidence intervals are simulated for the slope coefficients and the estimated threshold. However, the results for the different methods have very different economic implications. We perform a Monte Carlo experiment to evaluate the various methods.Bootstrap GDP; Threshold Autoregression; Bootstrap Confidence Intervals
Resonant tunneling of electromagnetic waves through polariton gaps
We consider resonant tunneling of electromagnetic waves through an optical
barrier formed by dielectric layers with the frequency dispersion of their
dielectric permiability. The frequency region between lower and upper polariton
branches in these materials presents a stop band for electromagnetic waves. We
show that resonance tunneling through this kind of barriers is qualitatevely
different from tunneling through other kind of optical barriers as well as from
quantum mechanic tunneling through a rectangular barrier. We find that the
width of the resonance maxima of the transmission coeffcient tends to zero as
frequency approach the lower boundary of the stop band in a very sharp
non-analytical way. Resonance transmission peaks give rise to new photonic
bands inside the stop band if one considers periodical array of the layers.Comment: 8 pages, 5 figure
Lorentz Invariant Superluminal Tunneling
It is shown that superluminal optical signalling is possible without
violating Lorentz invariance and causality via tunneling through photonic band
gaps in inhomogeneous dielectrics of a special kind.Comment: 10 pages revtex, no figure, more discussions added, submitted to
Phys. Rev.
Single Proton Knock-Out Reactions from 24,25,26F
The cross sections of the single proton knock-out reactions from 24F, 25F,
and 26F on a 12C target were measured at energies of about 50 MeV/nucleon.
Ground state populations of 6.6+-.9 mb, 3.8+-0.6 mb for the reactions
12C(24F,23O) and 12C(25F,24O) were extracted, respectively. The data were
compared to calculations based on the many-body shell model and the eikonal
theory. In the reaction 12C(26F,25O) the particle instability of 25O was
confirmed
Hydrogen-induced ferromagnetism in two-dimensional Pt dichalcogenides
Electronic, structural, and magnetic properties of Pt dichalcogenide monolayers are investigated using firstprinciple calculations.We find that hydrogenation lifts the spin degeneracy in narrow antibonding Pt 5d subband electrons and transforms the nonmagnetic semiconductors PtX2 (X = S,Se,Te) into ferromagnetic metals, PtX2-1H; neither strain nor thin-film edges are necessary to support the transition. The trend towards ferromagnetism is most pronounced for X = S, decreasing with increasing atomic weight of the chalcogens
Influence of Temperature and Concentration on the Self-Assembly of Nonionic CiEjSurfactants: A Light Scattering Study
Nonionic poly(ethylene oxide) alkyl ether (CiE) surfactants self-assemble into aggregates of various sizes and shapes above their critical micelle concentration (CMC). Knowledge on solution attributes such as CMC as well as aggregate characteristics is crucial to choose the appropriate surfactant for a given application, e.g., as a micellar solvent system. In this work, we used static and dynamic light scattering to measure the CMC, aggregation number (N), and hydrodynamic radius (R) of four different CE surfactants (CE, CE, CE, and CE). We examined the influence of temperature, concentration, and molecular structure on the self-assembly in the vicinity of the CMC. A minimum in the CMC vs temperature curve was identified for all surfactants investigated. Further, extending the hydrophilic and hydrophobic chain lengths leads to an increase and decrease of the CMC, respectively. The size of the aggregates strongly depends on temperature. N and R increase with increasing temperature for all surfactants investigated. Additionally, N and R both increase with increasing surfactant concentration. The data obtained in this work further improve the understanding of the influence of temperature and molecular structure on the self-assembly of CiE surfactants and will further foster their use in micellar solvent systems
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