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7th IEEE International Conference on Data science in Cyberspace, DSC 2022

作者： Liu, Ling Liu, Xin Zhao, Yue Hu, Ning Cyberspace Institute of Advanced Technology GuangZhou University Guangzhou510006 China ChangSha University College of Computer Engineering and Applied Math Changsha410022 China Science and Technology on Communication Security Laboratory Chengdu610041 China Peng Cheng Laboratory Shenzhen518000 China

ISBN: (数字)9781665474801

ISBN: (纸本)9781665474801

Anonymous networks hide communication content and communication relationships by encrypting the content and transmission path of traffic. But the website fingerprinting attack can determine the websites a user visits by analyzing the user's traffic patterns and website fingerprints without decrypting the traffic. To defend against website fingerprinting attacks, most of the existing methods reduce the accuracy of analysis by increasing the access delay and background traffic. Unfortunately, such methods not only degrade the user experience, but also affect the performance of anonymity networks. By adopting the Tor pluggable transmission technology, this paper proposes a new targeted, lightweight defense to against website fingerprinting attack (TLD-WF). TLD-WF uses the TLD-flow module to obtain the analyzed flow information with an accuracy rate of over 90%, and conducts targeted dynamic scrambling. TLD-WF not only effectively guarantees the anonymity and security of Tor users, but also has the advantages of zero latency overhead and low bandwidth overhead. The experimental results show that TLD-flow can reduce the analysis accuracy of the CNN classifier from 93.2% to around 8.3% under normal conditions. With guaranteed zero latency and 45% bandwidth overhead, the analytical accuracy of the CNN classifier will be reduced by about 50%. © 2022 IEEE.

关键词： Websites

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Adjoint-Free 4D-Var Methods Via Line Search Optimization For Non-Linear Data Assimilation

arXiv

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arXiv 2023年

作者： Nino-Ruiz, Elias D. Diaz-Rodriguez, Jairo Applied Math and Computer Science Laboratory Department of Computer Science Universidad del Norte Colombia Department of Mathematics and Statistics York University Canada

This paper proposes two practical implementations of Four-Dimensional Variational (4D-Var) Ensemble Kalman Filter (4D-EnKF) methods for non-linear data assimilation. Our formulations' main idea is to avoid the intrinsic need for adjoint models in the context of 4D-Var optimization and, even more, to handle non-linear observation operators during the assimilation of observations. The proposed methods work as follows: snapshots of an ensemble of model realizations are taken at observation times, these snapshots are employed to build control spaces onto which analysis increments can be estimated. Via the linearization of observation operators at observation times, a line-search based optimization method is proposed to estimate optimal analysis increments. The convergence of this method is theoretically proven as long as the dimension of control-spaces equals model one. In the first formulation, control spaces are given by full-rank square root approximations of background error covariance matrices via the Bickel and Levina precision matrix estimator. In this context, we propose an iterative Woodbury matrix formula to perform the optimization steps efficiently. The last formulation can be considered as an extension of the Maximum Likelihood Ensemble Filter to the 4D-Var context. This employs pseudo-square root approximations of prior error covariance matrices to build control spaces. Experimental tests are performed by using the Lorenz 96 model. The results reveal that, in terms of Root-Mean-Square-Error values, both methods can obtain reasonable estimates of posterior error modes in the 4D-Var optimization problem. Moreover, the accuracies of the proposed filter implementations can be improved as the ensemble sizes are increased. © 2023, CC BY.

关键词： Optimization

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A Stochastic Covariance Shrinkage Approach in Ensemble Transform Kalman Filtering

arXiv

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arXiv 2020年

作者： Popov, Andrey A. Sandu, Adrian Nino-Ruiz, Elias D. Evensen, Geir Computational Science Laboratory Department of Computer Science Virginia Tech United States Applied Math and Computer Science Lab Universidad del Norte Colombia Norway

The Ensemble Kalman Filters (EnKF) employ a Monte-Carlo approach to represent covariance information, and are affected by sampling errors in operational settings where the number of model realizations is much smaller than the model state dimension. To alleviate the effects of these errors EnKF relies on model-specific heuristics such as covariance localization, which takes advantage of the spatial locality of correlations among the model variables. This work proposes an approach to alleviate sampling errors that utilizes a locally averaged-in-time dynamics of the model, described in terms of a climatological covariance of the dynamical system. We use this covariance as the target matrix in covariance shrinkage methods, and develop a stochastic covariance shrinkage approach where synthetic ensemble members are drawn to enrich both the ensemble subspace and the ensemble transformation. We additionally provide for a way in which this methodology can be localized similar to the state-of-the-art LETKF method, and that for a certain model setup, our methodology significantly outperforms it. Copyright © 2020, The Authors. All rights reserved.

关键词： Dynamical systems

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On the cost of recomputing: Tight bounds on pebbling with faults

On the cost of recomputing: Tight bounds on pebbling with fa...

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Proceedings of the 1994 21st International Colloquium on Automata, Languages and Programming, ICALP'94

作者： Aumann, Yonatan Bar-Ilan, Judit Feige, Uriel Department of Applied Math. The Weizmann Institute Rehovot Israel MIT Laboratory of Computer Science 545 Technology Square CambridgeMA02138 United States School of Library Archive and Information Studies The Hebrew University Jerusalem91904 Israel

ISBN: (纸本)9783540582014

We introduce a formal framework to study the time and space complexity of computing with faulty memory. For the fault-free case, time and space complexities were studied using the "pebbling game" model. We extend this model to the faulty case, where the content of memory cells may be erased. The model captures notions such as "check points" (keeping multiple copies of intermediate results), and "recovery" (partial recomputing in the case of failure). Using this model, we derive tight bounds on the time and/or space overhead inflicted by faults. As a lower bound, we exhibit cases where f worst-case faults may necessitate an Ω(f) multiplicative overhead in computation resources (time, space, or their product). The lower bound holds regardless of the computing and recomputing strategy employed. A matching upper-bound algorithm establishes that an O(f) multiplicative overhead always suffices. For the special class of tree computations, we show that faults can be handled with an O(f) additive factor in memory, and only a constant multiplicative overhead in time. © 1994, Springer Verlag. All rights reserved.

关键词： Artificial intelligence

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Constant-round oblivious transfer in the bounded storage model

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1st Theory of Cryptography Conference, TCC 2004

作者： Ding, Yan Zong Harnik, Danny Rosen, Alon Shaltiel, Ronen College of Computing Georgia Institute of Technology 801 Atlantic Drive AtlantaGA30332-0280 United States Dept. of Computer Science and Applied Math Weizmann Institute of Science Rehovot76100 Israel Laboratory for Computer Science Massachusetts Institute of Technology 200 Technology Square CambridgeMA02139 United States

ISBN: (纸本)3540210008

We present a constant round protocol for Oblivious Transfer in Maurer's bounded storage model. In this model, a long random string R is initially transmitted and each of the parties interacts based on a small portion of R. Even though the portions stored by the honest parties are small, security is guaranteed against any malicious party that remembers almost all of the string R. Previous constructions for Oblivious Transfer in the bounded storage model required polynomially many rounds of interaction. Our protocol has only 5 messages. We also improve other parameters, such as the number of bits transferred and the probability of immaturely aborting the protocol due to failure. Our techniques utilize explicit constructions from the theory of derandomization. In particular, we use constructions of almost t-wise independent permutations, randomness extractors and averaging samplers. © Springer-Verlag Berlin Heidelberg 2004.

关键词： computers

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Dynamic and recursive oil-reservoir proxy using Elman neural networks

Dynamic and recursive oil-reservoir proxy using Elman neural...

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2016 IEEE ANDESCON, ANDESCON 2016

作者： Tupac, Yvan Talavera, Alvaro Rivero, Cristian Rodriguez Computer Science School Universidad Católica San Pablo Arequipa Peru Department of Engineering Universidad Del Pacífico Lima Peru Math Research Laboratory Applied to Control Universidad Nacional de Córdoba Córdoba Argentina

ISBN: (纸本)9781509025312

In this work, a reservoir simulation approximation model (proxy) based on recurrent artificial neural networks is proposed. This model is intended to obtain rates of oil, gas and water production at time t+1 from the respective production rates, average pressure and water cut at t time and the well operation points to be applied in t + 1. Also, this model is able to follow the dynamics of the reservoir system applying online learning from real production observed values. Also, this model allows perform fast and accurate production forecasting for several steps using a recursive mechanism. This model will be inserted into an oil-production control tool to find the optimal operation conditions within a forecast horizon. The obtained outcomes over the approximation tests indicate the methodology is adequate to perform production forecasts. © 2016 IEEE.

关键词： Production control

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A new class of adaptive fuzzy control systems applied in an industrial thermal vacuum process

A new class of adaptive fuzzy control systems applied in an ...

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International Conference on Emerging Technologies and Factory Automation (ETFA)

作者： J.E. Araujo Filho S.A. Sandri E.E.N. Macau Computer Science and Applied Math Associated Laboratory-LAC Brazilian National Space Research Institute Sao Paulo Brazil Integrating and Testing Laboratory LIT Brazil

ISBN: (纸本)0780372417

A feasible solution to the problem of controlling thermal vacuum chambers automatically to satisfy testing requirements in the space sector is considered. The design of appropriate controllers is not a trivial task due to intrinsic time delay and changing dynamics related to variable operating conditions in thermal vacuum tests. The fuzzy reference gain-scheduling control approach (FRGS) is a concept that has been under development to substitute specialists in controlling thermal vacuum systems. In this new class of adaptive fuzzy controller the parameters are adjusted on-fine by modifying the shapes of the membership functions according to different operational conditions. Its application is not limited to controlling thermal vacuum processes. It can be applied to control any industrial problems or to model dynamics of systems, and it can be used in decision-making tasks.

关键词： Adaptive systems Programmable control Adaptive control Fuzzy control Thermal variables control Automatic control Control systems Shape control Automatic testing Delay effects

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Detecting lithium plating dynamics in a solid-state battery with operando X-ray computed tomography using machine learning

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npj Computational Materials 2023年第1期9卷 1402-1410页

作者： Ying Huang David Perlmutter Andrea Fei-Huei Su Jerome Quenum Pavel Shevchenko Dilworth Y.Parkinson Iryna V.Zenyuk Daniela Ushizima Department of Materials Science&Engineering University of California IrvineIrvineCaliforniaUSA National Fuel Cell Research Center University of California IrvineIrvineCaliforniaUSA Applied Math and Computational Research Division Lawrence Berkeley National LaboratoryBerkeleyCaliforniaUSA Department of Chemical&Biomolecular Engineering University of California IrvineIrvineCaliforniaUSA Department of Electrical Engineering and Computer Sciences College of EngineeringUniversity of California BerkeleyBerkeleyCaliforniaUSA Advanced Photon Source Argonne National Laboratory9700 South Cass AvenueLemontIllinoisUSA Advanced Light Source Lawrence Berkeley National LaboratoryBerkeleyCaliforniaUSA Berkeley Institute for Data Science University of California BerkeleyBerkeleyCaliforniaUSA

Operando X-ray micro-computed tomography(µCT)provides an opportunity to observe the evolution of Li structures inside pouch *** is an essential step to quantitatively analyzingµCT datasets but is challenging to achieve on operando Li-metal battery datasets due to the low X-ray attenuation of the Li metal and the sheer size of the ***,we report a computational approach,batteryNET,to train an Iterative Residual U-Net-based network to detect Li *** resulting semantic segmentation shows singular Li-related component changes,addressing diverse morphologies in the *** addition,visualizations of the dead Li are provided,including calculations about the volume and effective thickness of electrodes,deposited Li,and redeposited *** also report discoveries about the spatial relationships between these *** approach focuses on a method for analyzing battery performance,which brings insight that significantly benefits future Li-metal battery design and a semantic segmentation transferrable to other datasets.

关键词： battery lithium state

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INFLUENCE OF THE DISCRETIZATION STEP ON THE POSITIVITY OF CONFORMABLE FRACTIONAL LINEAR SYSTEMS

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UPB Scientific Bulletin, Series A: applied mathematics and Physics 2023年第1期85卷 77-86页

作者： Benuettou, Kamel Ghezzar, Mohammed Amine Bougada, Djillali Abdelhamid Ibn Badis University Mostaganem ACSY Team-Laboratory of Pure and Applied Math-ematics Department of Mathematics and Computer Science Faculty SEI BP 227/118 Mostaganem27000 Algeria National Higher School of Mathematics ACSY Team-Laboratory of Pure and Applied Mathematics Algeria

The effectiveness of this work lies in the influence of the discretization step on the positivity of the one-dimensional conformable fractional linear systems. A piecewise constant approximation method which converts a continuous fractional order derivative into a discrete time equation is presented as an alternative approach. It aims at investigating whether, how and when this step affects the positive continuous times models. To accomplish this research, a new test was developed and implemented in which the positivity conditions of the considered system was examined both before and after being exposed to the sampling step. i.e., under which conditions the one-dimensional discrete-time linear system obtained by discretization from the one-dimensional continuous time linear systems will be also positive if the one-dimensional continuous time linear system is positive. The new method presented is suggested to test the influence of the discretization step on the positivity of this class of systems. Finally, we discuss some numerical examples to illustrate the validity of the provided results. © 2023, Politechnica University of Bucharest. All rights reserved.

关键词： Linear systems

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Image Surveillance Assistant

Image Surveillance Assistant

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IEEE Winter Applications and computer Vision Workshops (WACVW)

作者： Michael Maynord Sambit Bhattacharya David W. Aha Computer Science Dept. University of Maryland College Park MD Dept. of Math & Computer Science Fayetteville State University Fayetteville NC Navy Center for Applied Research in AI Naval Research Laboratory Washington DC

Security watchstanders who monitor multiple videos over long periods of time can be susceptible to information overload and fatigue. To address this, we present a configurable perception pipeline architecture, called the Image Surveillance Assistant (ISA), for assisting watchstanders with video surveillance tasks. We also present ISA1, an initial implementation that can be configured with a set of context specifications which watchstanders can select or provide to indicate what imagery should generate notifications. ISA1's inputs include (1) an image and (2) context specifications, which contain English sentences and a decision boundary defined over object detection vectors. ISA1 assesses the match of the image with the contexts by comparing (1) detected versus specified objects and (2) automatically-generated versus specified captions. Finally, we present a study to assess the utility of using captions in ISA1, and found that they substantially improve the performance of image context detection.

关键词： Context Surveillance computer architecture Feature extraction Videos Security Object detection

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