4,775 research outputs found
Improved Successive Cancellation Decoding of Polar Codes
As improved versions of successive cancellation (SC) decoding algorithm,
successive cancellation list (SCL) decoding and successive cancellation stack
(SCS) decoding are used to improve the finite-length performance of polar
codes. Unified descriptions of SC, SCL and SCS decoding algorithms are given as
path searching procedures on the code tree of polar codes. Combining the ideas
of SCL and SCS, a new decoding algorithm named successive cancellation hybrid
(SCH) is proposed, which can achieve a better trade-off between computational
complexity and space complexity. Further, to reduce the complexity, a pruning
technique is proposed to avoid unnecessary path searching operations.
Performance and complexity analysis based on simulations show that, with proper
configurations, all the three improved successive cancellation (ISC) decoding
algorithms can have a performance very close to that of maximum-likelihood (ML)
decoding with acceptable complexity. Moreover, with the help of the proposed
pruning technique, the complexities of ISC decoders can be very close to that
of SC decoder in the moderate and high signal-to-noise ratio (SNR) regime.Comment: This paper is modified and submitted to IEEE Transactions on
Communication
A simple and natural interpretations of the DAMPE cosmic-ray electron/positron spectrum within two sigma deviations
The DArk Matter Particle Explorer (DAMPE) experiment has recently announced
the first results for the measurement of total electron plus positron fluxes
between 25 GeV and 4.6 TeV. A spectral break at about 0.9 TeV and a tentative
peak excess around 1.4 TeV have been found. However, it is very difficult to
reproduce both the peak signal and the smooth background including spectral
break simultaneously. We point out that the numbers of events in the two energy
ranges (bins) close to the 1.4 TeV excess have deficits. With the
basic physics principles such as simplicity and naturalness, we consider the
, , and deviations due to statistical
fluctuations for the 1229.3~GeV bin, 1411.4~GeV bin, and 1620.5~GeV bin.
Interestingly, we show that all the DAMPE data can be explained consistently
via both the continuous distributed pulsar and dark matter interpretations,
which have and (for all the 38
points in DAMPE electron/positron spectrum with 3 of them revised),
respectively. These results are different from the previous analyses by
neglecting the 1.4 TeV excess. At the same time, we do a similar global fitting
on the newly released CALET lepton data, which could also be interpreted by
such configurations. Moreover, we present a dark matter model with
Breit-Wigner mechanism, which can provide the proper dark matter annihilation
cross section and escape the CMB constraint. Furthermore, we suggest a few ways
to test our proposal.Comment: 18 pages, 6 figures, 5 tables. Figures and Bibs update
Should I Stay or Should I Go: Two Features to Help People Stop An Exploratory Search Wisely
poster abstractAs information becomes more ubiquitously available, many information users tend to experience a sense of anxiety due to the “information overload”. Few studies have systematically examined searchers’ stopping behavior, i.e., how users recognize how much information is enough to terminate a search. Bad decisions on a stopping point will lead to either insufficient information or unnecessary waste of time and effort without much additional information gain. Understanding searchers’ stopping behavior is extremely important to assist in thorough search result evaluation and to prevent a premature or a too-late search stopping. In this study, we present the design and implementation of two search techniques: Result Preview (RP) and History Review (HR), to help people make right decisions about when to terminate a search and how to consume information efficiently when facing an overwhelming amount of information. The basic idea of RP is to visualize the distribution of newly retrieved and re-retrieved documents to users, and that of HR is to display the previous search activities for searchers to review what has been done to help define the next steps. Both features are aiming at guiding searchers through the process of problem solving and decision making about whether to stay or leave during the search process. To implement the two techniques, we developed the search system on Bing Search API. The Bing search results were brought back to the search interface using AJAX and PHP. A formal user experiment with 24 participants is also proposed to evaluate the benefits and limitations, and also inform the future RP and HR design
Hankel determinants, Pad\'e approximations, and irrationality exponents
The irrationality exponent of an irrational number , which measures the
approximation rate of by rationals, is in general extremely difficult to
compute explicitly, unless we know the continued fraction expansion of .
Results obtained so far are rather fragmentary, and often treated case by case.
In this work, we shall unify all the known results on the subject by showing
that the irrationality exponents of large classes of automatic numbers and
Mahler numbers (which are transcendental) are exactly equal to . Our classes
contain the Thue--Morse--Mahler numbers, the sum of the reciprocals of the
Fermat numbers, the regular paperfolding numbers, which have been previously
considered respectively by Bugeaud, Coons, and Guo, Wu and Wen, but also new
classes such as the Stern numbers and so on. Among other ingredients, our
proofs use results on Hankel determinants obtained recently by Han.Comment: International Mathematics Research Notices 201
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