72,682 research outputs found
Understanding of the Retarded Oxidation Effects in Silicon Nanostructures
In-depth understanding of the retarded oxidation phenomenon observed during
the oxidation of silicon nanostructures is proposed. The wet thermal oxidation
of various silicon nanostructures such as nanobeams, concave/convex nanorings
and nanowires exhibits an extremely different and complex behavior. Such
effects have been investigated by the modeling of the mechanical stress
generated during the oxidation process explaining the retarded regime. The
model describes the oxidation kinetics of silicon nanowires down to a few
nanometers while predicting reasonable and physical stress levels at the
Si/SiO interface by correctly taking into account the relaxation effects
in silicon oxide through plastic flow
Polarized Curvature Radiation in Pulsar Magnetosphere
The propagation of polarized emission in pulsar magnetosphere is investigated
in this paper. The polarized waves are generated through curvature radiation
from the relativistic particles streaming along curved magnetic field lines and
co-rotating with the pulsar magnetosphere. Within the 1/{\deg} emission cone,
the waves can be divided into two natural wave mode components, the ordinary
(O) mode and the extraord nary (X) mode, with comparable intensities. Both
components propagate separately in magnetosphere, and are aligned within the
cone by adiabatic walking. The refraction of O-mode makes the two components
separated and incoherent. The detectable emission at a given height and a given
rotation phase consists of incoherent X-mode and O-mode components coming from
discrete emission regions. For four particle-density models in the form of
uniformity, cone, core and patches, we calculate the intensities for each mode
numerically within the entire pulsar beam. If the co-rotation of relativistic
particles with magnetosphere is not considered, the intensity distributions for
the X-mode and O-mode components are quite similar within the pulsar beam,
which causes serious depolarization. However, if the co-rotation of
relativistic particles is considered, the intensity distributions of the two
modes are very different, and the net polarization of out-coming emission
should be significant. Our numerical results are compared with observations,
and can naturally explain the orthogonal polarization modes of some pulsars.
Strong linear polarizations of some parts of pulsar profile can be reproduced
by curvature radiation and subsequent propagation effect.Comment: 12 pages, 9 figures, Accepted for publication in MNRA
A Model of Trade with Ricardian Comparative Advantage and Intra-sectoral Firm Heterogeneity
In this paper, we merge the heterogenous firm trade model of Melitz (2003) with the Ricardian model of Dornbusch, Fisher and Samuelson (DFS 1977) to explain how the pattern of international specialization and trade is determined by the interaction of comparative advantage, economies of scale, country sizes and trade barriers. The model is able to capture the existence of inter-industry trade and intra-industry trade in a single unified framework. It explains how trade openness affects the pattern of international specialization and trade. It generalizes Melitz’s firm selection effect in the face of trade liberalization to a setting where the patterns of inter-industry trade and intra-industry are endogenous. Although opening to trade is unambiguously welfare-improving in both countries, trade liberalization can lead to an counter-Melitz effect in the larger country if it is insufficiently competitive in the sectors where it has the strongest comparative disadvantage but still produces. In this case, the operating productivity cutoff is lowered while the exporting cutoff increases in the face of trade liberalization. This is because the intersectoral resource allocation (IRA) effect dominates the Melitz effect in these sectors. Consequently, the larger country can lose from trade liberalization. Some hypotheses related to firms’ exporting behavior across sectors upon opening up to trade and upon trade liberalization are also derived. Analyses of firm-level data of Chinese manufacturing sectors confirm these hypotheses.inter-industry trade, intra-industry trade, heterogeneous firms, trade liberalization
An easy-to-use diagnostic system development shell
The Diagnostic System Development Shell (DSDS), an expert system development shell for diagnostic systems, is described. The major objective of building the DSDS is to create a very easy to use and friendly environment for knowledge engineers and end-users. The DSDS is written in OPS5 and CommonLisp. It runs on a VAX/VMS system. A set of domain independent, generalized rules is built in the DSDS, so the users need not be concerned about building the rules. The facts are explicitly represented in a unified format. A powerful check facility which helps the user to check the errors in the created knowledge bases is provided. A judgement facility and other useful facilities are also available. A diagnostic system based on the DSDS system is question driven and can call or be called by other knowledge based systems written in OPS5 and CommonLisp. A prototype diagnostic system for diagnosing a Philips constant potential X-ray system has been built using the DSDS
The triple degenerate star WD1704+481
WD1704+481 is a visual binary in which both components are white dwarfs. We
present spectra of the H-alpha line of both stars which show that one component
(WD1704+481.2 = Sanduleak B = GR 577) is a close binary with two white dwarf
components. Thus, WD1704+481 is the first known triple degenerate star. From
radial velocity measurements of the close binary we find an orbital period of
0.1448d, a mass ratio, q=Mbright/Mfaint of q=0.70+-0.03 and a difference in the
gravitational redshifts of 11.5+-2.3km/s. The masses of the close pair of white
dwarfs predicted by the mass ratio and gravitational redshift difference
combined with theoretical cooling curves are 0.39+-0.05 solar mass and
0.56+-0.07 solar masses. WD1704+481 is therefore also likely to be the first
example of a double degenerate in which the less massive white dwarf is
composed of helium and the other white dwarf is composed of carbon and oxygen.Comment: 5 pages, 4 figure
Asymptotics of Spinfoam Amplitude on Simplicial Manifold: Lorentzian Theory
The present paper studies the large-j asymptotics of the Lorentzian EPRL
spinfoam amplitude on a 4d simplicial complex with an arbitrary number of
simplices. The asymptotics of the spinfoam amplitude is determined by the
critical configurations. Here we show that, given a critical configuration in
general, there exists a partition of the simplicial complex into three type of
regions R_{Nondeg}, R_{Deg-A}, R_{Deg-B}, where the three regions are
simplicial sub-complexes with boundaries. The critical configuration implies
different types of geometries in different types of regions, i.e. (1) the
critical configuration restricted into R_{Nondeg} is degenerate of type-A in our definition of degeneracy, but implies
a nondegenerate discrete Euclidean geometry on R_{Deg-A}, (3) the critical
configuration restricted into R_{Deg-B} is degenerate of type-B, and implies a
vector geometry on R_{Deg-B}. With the critical configuration, we further make
a subdivision of the regions R_{Nondeg} and R_{Deg-A} into sub-complexes (with
boundary) according to their Lorentzian/Euclidean oriented 4-simplex volume
V_4(v), such that sgn(V_4(v)) is a constant sign on each sub-complex. Then in
the each sub-complex, the spinfoam amplitude at the critical configuration
gives the Regge action in Lorentzian or Euclidean signature respectively on
R_{Nondeg} or R_{Deg-A}. The Regge action reproduced here contains a sign
factor sgn(V_4(v)) of the oriented 4-simplex volume. Therefore the Regge action
reproduced here can be viewed a discretized Palatini action with on-shell
connection. Finally the asymptotic formula of the spinfoam amplitude is given
by a sum of the amplitudes evaluated at all possible critical configurations,
which are the products of the amplitudes associated to different type of
geometries.Comment: 54 pages, 2 figures, reference adde
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