13,184 research outputs found
Current Dissipation in Thin Superconducting Wires: Accurate Numerical Evaluation Using the String Method
Current dissipation in thin superconducting wires is numerically evaluated by
using the string method, within the framework of time-dependent Ginzburg-Landau
equation with a Langevin noise term. The most probable transition pathway
between two neighboring current-carrying metastable states, continuously
linking the Langer-Ambegaokar saddle-point state to a state in which the order
parameter vanishes somewhere, is found numerically. We also give a numerically
accurate algorithm to evaluate the prefactors for the rate of current-reducing
transitions.Comment: 25 pages, 5 figure
Mining frequent biological sequences based on bitmap without candidate sequence generation
Biological sequences carry a lot of important genetic information of organisms. Furthermore, there is an inheritance law related to protein function and structure which is useful for applications such as disease prediction. Frequent sequence mining is a core technique for association rule discovery, but existing algorithms suffer from low efficiency or poor error rate because biological sequences differ from general sequences with more characteristics. In this paper, an algorithm for mining Frequent Biological Sequence based on Bitmap, FBSB, is proposed. FBSB uses bitmaps as the simple data structure and transforms each row into a quicksort list QS-list for sequence growth. For the continuity and accuracy requirement of biological sequence mining, tested sequences used during the mining process of FBSB are real ones instead of generated candidates, and all the frequent sequences can be mined without any errors. Comparing with other algorithms, the experimental results show that FBSB can achieve a better performance on both run time and scalability
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Rethinking Secure Precoding via Interference Exploitation: A Smart Eavesdropper Perspective
Based on the concept of constructive interference (CI), multiuser
interference (MUI) has recently been shown to be beneficial for communication
secrecy. A few CI-based secure precoding algorithms have been proposed that use
both the channel state information (CSI) and knowledge of the instantaneous
transmit symbols. In this paper, we examine the CI-based secure precoding
problem with a focus on smart eavesdroppers that exploit statistical
information gleaned from the precoded data for symbol detection. Moreover, the
impact of correlation between the main and eavesdropper channels is taken into
account. We first modify an existing CI-based preocding scheme to better
utilize the destructive impact of the interference. Then, we point out the
drawback of both the existing and the new modified CI-based precoders when
faced with a smart eavesdropper. To address this deficiency, we provide a
general principle for precoder design and then give two specific design
examples. Finally, the scenario where the eavesdropper's CSI is unavailable is
studied. Numerical results show that although our modified CI-based precoder
can achieve a better energy-secrecy trade-off than the existing approach, both
have a limited secrecy benefit. On the contrary, the precoders developed using
the new CI-design principle can achieve a much improved trade-off and
significantly degrade the eavesdropper's performance
Single item stochastic lot sizing problem considering capital flow and business overdraft
This paper introduces capital flow to the single item stochastic lot sizing
problem. A retailer can leverage business overdraft to deal with unexpected
capital shortage, but needs to pay interest if its available balance goes below
zero. A stochastic dynamic programming model maximizing expected final capital
increment is formulated to solve the problem to optimality. We then investigate
the performance of four controlling policies: (), (), () and
(, , ); for these policies, we adopt simulation-genetic
algorithm to obtain approximate values of the controlling parameters. Finally,
a simulation-optimization heuristic is also employed to solve this problem.
Computational comparisons among these approaches show that policy and
policy provide performance close to that of optimal
solutions obtained by stochastic dynamic programming, while
simulation-optimization heuristic offers advantages in terms of computational
efficiency. Our numerical tests also show that capital availability as well as
business overdraft interest rate can substantially affect the retailer's
optimal lot sizing decisions.Comment: 18 pages, 3 figure
ZOOpt: Toolbox for Derivative-Free Optimization
Recent advances of derivative-free optimization allow efficient approximating
the global optimal solutions of sophisticated functions, such as functions with
many local optima, non-differentiable and non-continuous functions. This
article describes the ZOOpt (https://github.com/eyounx/ZOOpt) toolbox that
provides efficient derivative-free solvers and are designed easy to use. ZOOpt
provides a Python package for single-thread optimization, and a light-weighted
distributed version with the help of the Julia language for Python described
functions. ZOOpt toolbox particularly focuses on optimization problems in
machine learning, addressing high-dimensional, noisy, and large-scale problems.
The toolbox is being maintained toward ready-to-use tool in real-world machine
learning tasks
Understanding Kernel Size in Blind Deconvolution
Most blind deconvolution methods usually pre-define a large kernel size to
guarantee the support domain. Blur kernel estimation error is likely to be
introduced, yielding severe artifacts in deblurring results. In this paper, we
first theoretically and experimentally analyze the mechanism to estimation
error in oversized kernel, and show that it holds even on blurry images without
noises. Then to suppress this adverse effect, we propose a low rank-based
regularization on blur kernel to exploit the structural information in degraded
kernels, by which larger-kernel effect can be effectively suppressed. And we
propose an efficient optimization algorithm to solve it. Experimental results
on benchmark datasets show that the proposed method is comparable with the
state-of-the-arts by accordingly setting proper kernel size, and performs much
better in handling larger-size kernels quantitatively and qualitatively. The
deblurring results on real-world blurry images further validate the
effectiveness of the proposed method.Comment: Accepted by WACV 201
Subject-specific finite element modelling of the human hand complex : muscle-driven simulations and experimental validation
This paper aims to develop and validate a subject-specific framework for modelling the human hand. This was achieved by combining medical image-based finite element modelling, individualized muscle force and kinematic measurements. Firstly, a subject-specific human hand finite element (FE) model was developed. The geometries of the phalanges, carpal bones, wrist bones, ligaments, tendons, subcutaneous tissue and skin were all included. The material properties were derived from in-vivo and in-vitro experiment results available in the literature. The boundary and loading conditions were defined based on the kinematic data and muscle forces of a specific subject captured from the in-vivo grasping tests. The predicted contact pressure and contact area were in good agreement with the in-vivo test results of the same subject, with the relative errors for the contact pressures all being below 20%. Finally, sensitivity analysis was performed to investigate the effects of important modelling parameters on the predictions. The results showed that contact pressure and area were sensitive to the material properties and muscle forces. This FE human hand model can be used to make a detailed and quantitative evaluation into biomechanical and neurophysiological aspects of human hand contact during daily perception and manipulation. The findings can be applied to the design of the bionic hands or neuro-prosthetics in the future
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