57,908 research outputs found
Role of internal gases and creep of Ag in controlling the critical current density of Ag-sheathed Bi2Sr2CaCu2Ox wires
High engineering critical current density JE of >500 A/mm2 at 20 T and 4.2 K
can be regularly achieved in Ag-sheathed multifilamentary Bi2Sr2CaCu2Ox
(Bi-2212) round wire when the sample length is several centimeters. However,
JE(20 T) in Bi-2212 wires of several meters length, as well as longer pieces
wound in coils, rarely exceeds 200 A/mm2. Moreover, long-length wires often
exhibit signs of Bi-2212 leakage after melt processing that are rarely found in
short, open-end samples. We studied the length dependence of JE of
state-of-the-art powder-in-tube (PIT) Bi-2212 wires and gases released by them
during melt processing using mass spectroscopy, confirming that JE degradation
with length is due to wire swelling produced by high internal gas pressures at
elevated temperatures [1,2]. We further modeled the gas transport in Bi-2212
wires and examined the wire expansion at critical stages of the melt processing
of as-drawn PIT wires and the wires that received a degassing treatment or a
cold-densification treatment before melt processing. These investigations
showed that internal gas pressure in long-length wires drives creep of the Ag
sheath during the heat treatment, causing wire to expand, lowering the density
of Bi-2212 filaments, and therefore degrading the wire JE; the creep rupture of
silver sheath naturally leads to the leakage of Bi-2212 liquid. Our work shows
that proper control of such creep is the key to preventing Bi-2212 leakage and
achieving high JE in long-length Bi-2212 conductors and coils
Accelerator measurement of the energy spectra of neutrons emitted in the interaction of 3-GeV protons with several elements
The application of time of flight techniques for determining the shapes of the energy spectra of neutrons between 20 and 400 MeV is discussed. The neutrons are emitted at 20, 34, and 90 degrees in the bombardment of targets by 3 GeV protons. The targets used are carbon, aluminum, cobalt, and platinum with cylindrical cross section. Targets being bombarded are located in the internal circulating beam of a particle accelerator
Anti-correlation and subsector structure in financial systems
With the random matrix theory, we study the spatial structure of the Chinese
stock market, American stock market and global market indices. After taking
into account the signs of the components in the eigenvectors of the
cross-correlation matrix, we detect the subsector structure of the financial
systems. The positive and negative subsectors are anti-correlated each other in
the corresponding eigenmode. The subsector structure is strong in the Chinese
stock market, while somewhat weaker in the American stock market and global
market indices. Characteristics of the subsector structures in different
markets are revealed.Comment: 6 pages, 2 figures, 4 table
Realizing quantum controlled phase-flip gate through quantum dot in silicon slow-light photonic crystal waveguide
We propose a scheme to realize controlled phase gate between two single
photons through a single quantum dot in slow-light silicon photonic crystal
waveguide. Enhanced Purcell factor and beta factor lead to high gate fidelity
over broadband frequencies compared to cavity-assisted system. The excellent
physical integration of this silicon photonic crystal waveguide system provides
tremendous potential for large-scale quantum information processing.Comment: 9 pages, 3 figure
On the Stanley Depth of Squarefree Veronese Ideals
Let be a field and . In 1982, Stanley defined what is
now called the Stanley depth of an -module , denoted \sdepth(M), and
conjectured that \depth(M) \le \sdepth(M) for all finitely generated
-modules . This conjecture remains open for most cases. However, Herzog,
Vladoiu and Zheng recently proposed a method of attack in the case when with being monomial -ideals. Specifically, their method
associates with a partially ordered set. In this paper we take advantage of
this association by using combinatorial tools to analyze squarefree Veronese
ideals in . In particular, if is the squarefree Veronese ideal
generated by all squarefree monomials of degree , we show that if , then \sdepth(I_{n,d})= \floor{\binom{n}{d+1}\Big/\binom{n}{d}}+d,
and if and , then d+3\le \sdepth(I_{n,d}) \le
\floor{\binom{n}{d+1}\Big/\binom{n}{d}}+d.Comment: 10 page
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