14,095 research outputs found
Current understanding of point defects and diffusion processes in silicon
The effects of oxidation of Si which established that vacancies (V) and Si self interstitials (I) coexist in Si at high temperatures under thermal equilibrium and oxidizing conditions are discussed. Some essential points associated with Au diffusion in Si are then discussed. Analysis of Au diffusion results allowed a determination of the I component and an estimate of the V component of the Si self diffusion coefficient. A discussion of theories on high concentration P diffusion into Si is then presented. Although presently there still is no theory that is completely satisfactory, significant progresses are recently made in treating some essential aspects of this subject
Fundamental constants and tests of theory in Rydberg states of one-electron ions
The nature of the theory of circular Rydberg states of hydrogenlike ions
allows highly-accurate predictions to be made for energy levels. In particular,
uncertainties arising from the problematic nuclear size correction which beset
low angular-momentum states are negligibly small for the high angular-momentum
states. The largest remaining source of uncertainty can be addressed with the
help of quantum electrodynamics (QED) calculations, including a new
nonperturbative result reported here. More stringent tests of theory and an
improved determination of the Rydberg constant may be possible if predictions
can be compared with precision frequency measurements in this regime. The
diversity of information can be increased by utilizing a variety of
combinations of ions and Ryberg states to determine fundamental constants and
test theory.Comment: 10 pages; LaTe
Aharonov-Bohm oscillations of a tunable quantum ring
With an atomic force microscope a ring geometry with self-aligned in-plane
gates was directly written into a GaAs/AlGaAs-heterostructure. Transport
measurements in the open regime show only one transmitting mode and
Aharonov-Bohm oscillations with more than 50% modulation are observed in the
conductance. The tuning via in-plane gates allows to study the Aharonov-Bohm
effect in the whole range from the open ring to the Coulomb-blockade regime.Comment: 3 pages, 3 figure
Observation of thundercloud-related gamma rays and neutrons in Tibet
During the 2010 rainy season in Yangbajing (4300 m above sea level) in Tibet, China, a long-duration count enhancement associated with thunderclouds was detected by a solar-neutron telescope and neutron monitors installed at the Yangbajing Comic Ray Observatory. The event, lasting for ∼40  min, was observed on July 22, 2010. The solar-neutron telescope detected significant γ-ray signals with energies >40  MeV in the event. Such a prolonged high-energy event has never been observed in association with thunderclouds, clearly suggesting that electron acceleration lasts for 40 min in thunderclouds. In addition, Monte Carlo simulations showed that >10  MeV γ rays largely contribute to the neutron monitor signals, while >1  keV neutrons produced via a photonuclear reaction contribute relatively less to the signals. This result suggests that enhancements of neutron monitors during thunderstorms are not necessarily clear evidence for neutron production, as previously thought
Enhancing Big Data Security with Collaborative Intrusion Detection
As an asset of Cloud computing, big data is now changing our business models and applications. Rich information residing in big data is driving business decision making to be a data-driven process. Its security and privacy, however, have always been a concern of the owners of the data. The security and privacy could be strengthened via securing Cloud computing environments. This requires a comprehensive security solution from attack prevention to attack detection. Intrusion Detection Systems (IDSs) are playing an increasingly important role within the realm of a set of network security schemes. In this article, we study the vulnerabilities in Cloud computing and propose a collaborative IDS framework to enhance the security and privacy of big data
Supergravity Higgs Inflation and Shift Symmetry in Electroweak Theory
We present a model of inflation in a supergravity framework in the Einstein
frame where the Higgs field of the next to minimal supersymmetric standard
model (NMSSM) plays the role of the inflaton. Previous attempts which assumed
non-minimal coupling to gravity failed due to a tachyonic instability of the
singlet field during inflation. A canonical K\"{a}hler potential with
\textit{minimal coupling} to gravity can resolve the tachyonic instability but
runs into the -problem. We suggest a model which is free of the
-problem due to an additional coupling in the K\"{a}hler potential which
is allowed by the Standard Model gauge group. This induces directions in the
potential which we call K-flat. For a certain value of the new coupling in the
(N)MSSM, the K\"{a}hler potential is special, because it can be associated with
a certain shift symmetry for the Higgs doublets, a generalization of the shift
symmetry for singlets in earlier models. We find that K-flat direction has
This shift symmetry is broken by interactions coming from
the superpotential and gauge fields. This direction fails to produce successful
inflation in the MSSM but produces a viable model in the NMSSM. The model is
specifically interesting in the Peccei-Quinn (PQ) limit of the NMSSM. In this
limit the model can be confirmed or ruled-out not just by cosmic microwave
background observations but also by axion searches.Comment: matches the published version at JCA
Quantum homodyne tomography with a priori constraints
I present a novel algorithm for reconstructing the Wigner function from
homodyne statistics. The proposed method, based on maximum-likelihood
estimation, is capable of compensating for detection losses in a numerically
stable way.Comment: 4 pages, REVTeX, 2 figure
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