223,868 research outputs found
Magnetic moments of exotic pentaquark baryons
In this talk, we present our recent investigation on the magnetic moments of
the exotic pentaquark states, based on the chiral quark-soliton model, all
relevant intrinsic parameters being fixed by using empirical data.Comment: 5 pages, 1 figure, a talk presented at the 10th International
Conference on Baryons (Baryons04), Palaiseau, October 25-29, 200
Crime Scene Re-investigation: A Postmortem Analysis of Game Account Stealers' Behaviors
As item trading becomes more popular, users can change their game items or
money into real money more easily. At the same time, hackers turn their eyes on
stealing other users game items or money because it is much easier to earn
money than traditional gold-farming by running game bots. Game companies
provide various security measures to block account- theft attempts, but many
security measures on the user-side are disregarded by users because of lack of
usability. In this study, we propose a server-side account theft detection
system base on action sequence analysis to protect game users from malicious
hackers. We tested this system in the real Massively Multiplayer Online Role
Playing Game (MMORPG). By analyzing users full game play log, our system can
find the particular action sequences of hackers with high accuracy. Also, we
can trace where the victim accounts stolen money goes.Comment: 7 pages, 8 figures, In Proceedings of the 15th Annual Workshop on
Network and Systems Support for Games (NetGames 2017
Fractional Imputation in Survey Sampling: A Comparative Review
Fractional imputation (FI) is a relatively new method of imputation for
handling item nonresponse in survey sampling. In FI, several imputed values
with their fractional weights are created for each missing item. Each
fractional weight represents the conditional probability of the imputed value
given the observed data, and the parameters in the conditional probabilities
are often computed by an iterative method such as EM algorithm. The underlying
model for FI can be fully parametric, semiparametric, or nonparametric,
depending on plausibility of assumptions and the data structure.
In this paper, we give an overview of FI, introduce key ideas and methods to
readers who are new to the FI literature, and highlight some new development.
We also provide guidance on practical implementation of FI and valid
inferential tools after imputation. We demonstrate the empirical performance of
FI with respect to multiple imputation using a pseudo finite population
generated from a sample in Monthly Retail Trade Survey in US Census Bureau.Comment: 26 pages, 2 figure
Predictive mean matching imputation in survey sampling
Predictive mean matching imputation is popular for handling item nonresponse
in survey sampling. In this article, we study the asymptotic properties of the
predictive mean matching estimator of the population mean. For variance
estimation, the conventional bootstrap inference for matching estimators with
fixed matches has been shown to be invalid due to the nonsmoothness nature of
the matching estimator. We propose asymptotically valid replication variance
estimation. The key strategy is to construct replicates of the estimator
directly based on linear terms, instead of individual records of variables.
Extension to nearest neighbor imputation is also discussed. A simulation study
confirms that the new procedure provides valid variance estimation.Comment: 20 pages, 0 figure, 1 tabl
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