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Selected Recent Applications of Sparse Grids

Numerical Mathematics(Theory,Methods and Applications) 2015年第1期8卷 47-77页

作者： Benjamin Peherstorfer Christoph Kowitz Dirk Pfluger Hans-Joachim Bungartz Scientific Computing Group Dept.of Computer ScienceBoltzmannstr.385748 GarchingGermany Institutefor Advanced Study Technische UniversitätMünchenLichtenbergstr.2a85748 GarchingGermany Institute for Parallel and Distributed Systems University of StuttgartUni-versitätsstr.3870569 StuttgartGermany

Sparse grids have become a versatile tool for a vast range of applications reaching from interpolation and numerical quadrature to data-driven problems and uncertainty *** review four selected real-world applications of sparse grids:financial product pricing with the Black-Scholes model,interactive explo-ration of simulation data with sparse-grid-based surrogate models,analysis of simu-lation data through sparse grid data mining methods,and stability investigations of plasma turbulence simulations.

关键词： Sparse grids hierarchical decomposition adaptivity combination technique

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The Interplay Between Timeliness and Scalability in Cloud Monitoring Systems

The Interplay Between Timeliness and Scalability in Cloud Mo...

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IEEE Symposium on computers and Communication

作者： Guilherme da Cunha Rodrigues Rodrigo N. Calheiros Marcio Barbosa de Carvalho Carlos Raniery Paula dos Santos Lisandro Zambenedetti Granville Liane Tarouco Rajkumar Buyya Computer Networks Group Institute of Informatics Federal University of Rio Grande do Sul Cloud Computing and Distributed Systems (CLOUDS) Laboratory Department of Computing and Information Systems The University of Melbourne Department of Applied Computing Federal University of Santa Maria

ISBN: (纸本)9781467371957

Cloud computing is a groundbreaking solution to acquire computational resources on demand. To deliver high quality cloud services and provide features such as reduced costs and availability to customers, a cloud, like any other computational system, needs to be properly managed in accordance with its characteristics (e.g., scalability, elasticity, timeliness). In this scenario, cloud monitoring is a key to achieve it. To properly work, cloud monitoring systems need to meet several requirements such as scalability, accuracy, and timeliness. This paper aims to unveil the trade-off between timeliness and scalability. Evaluations demonstrate the mutual influence between scalability and timeliness based on monitoring parameters (e.g., monitoring topologies, frequency sampling). Results show that non-deep monitoring topologies and decreasing the frequency sampling assist to reduce the mutual influence between timeliness and scalability.

关键词： Scalability CLOUDS Clouds monitoring systems Monitoring parameters Cloud computing

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Density estimation with adaptive sparse grids for large data sets 14

Density estimation with adaptive sparse grids for large data...

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14th SIAM International Conference on Data Mining, SDM 2014

作者： Peherstorfer, Benjamin Pflüger, Dirk Bungartz, Hans-Joachim Aerospace Computational Design Laboratory AeroAstro Massachusetts Institute of Technology United States Simulation of Large Systems Group Institute for Parallel and Distributed Systems University of Stuttgart Germany Scientific Computing Group Department of Computer Science Technische Universität München Germany

ISBN: (纸本)9781510811515

Nonparametric density estimation is a fundamental problem of statistics and data mining. Even though kernel density estimation is the most widely used method, its performance highly depends on the choice of the kernel bandwidth, and it can become computationally expensive for large data sets. WTe present an adaptive sparse-grid-based density estimation method which discretizes the estimated density function on basis functions centered at grid points rather than on kernels centered at the data points. Thus, the costs of evaluating the estimated density function are independent from the number of data points. We give details on how to estimate density functions on sparse grids and develop a cross validation technique for the parameter selection. We show numerical results to confirm that our sparse-grid-based method is well-suited for large data sets, and, finally, employ our method for the classification of astronomical objects to demonstrate that it is competitive to current kernel-based density estimation approaches with respect to classification accuracy and runtime. Copyright © SIAM.

关键词： Data mining

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RFA-Cut: Semi-automatic Segmentation of Radiofrequency Ablation Zones with and without Needles via Optimal s-t-Cuts

RFA-Cut: Semi-automatic Segmentation of Radiofrequency Ablat...

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Annual International Conference of the IEEE Engineering in Medicine and Biology Society

作者： Jan Egger Harald Busse Philipp Brandmaier Daniel Seider Matthias Gawlitza Steffen Strocka Philip Voglreiter Mark Dokter Michael Hofmann Bernhard Kainz Xiaojun Chen Alexander Hann Pedro Boechat Wei Yu Bernd Freisleben Tuomas Alhonnoro Mika Pollari Michael Moche Dieter Schmalstieg Institute for Computer Graphics and Vision Graz University of Technology Austria Dept. of Diagnostic and Interventional Radiology Leipzig University Hospital Germany Dept. of Computing Imperial College London UK School of Mechanical Engineering Shanghai Jiao Tong University Shanghai China Dept. of Internal Medicine and Gastroenterology Katharinenhospital Stuttgart Germany Distributed Systems Group Philipp University of Marburg Germany School of Science Aalto University Espoo Finland

ISBN: (纸本)9781424492695

In this contribution, we present a semi-automatic segmentation algorithm for radiofrequency ablation (RFA) zones via optimal s-t-cuts. Our interactive graph-based approach builds upon a polyhedron to construct the graph and was specifically designed for computed tomography (CT) acquisitions from patients that had RFA treatments of Hepatocellular Carcinomas (HCC). For evaluation, we used twelve post-interventional CT datasets from the clinical routine and as evaluation metric we utilized the Dice Similarity Coefficient (DSC), which is commonly accepted for judging computer aided medical segmentation tasks. Compared with pure manual slice-by-slice expert segmentations from interventional radiologists, we were able to achieve a DSC of about eighty percent, which is sufficient for our clinical needs. Moreover, our approach was able to handle images containing (DSC=75.9%) and not containing (78.1%) the RFA needles still in place. Additionally, we found no statistically significant difference (p<0.423) between the segmentation results of the subgroups for a Mann-Whitney test. Finally, to the best of our knowledge, this is the first time a segmentation approach for CT scans including the RFA needles is reported and we show why another state-of-the-art segmentation method fails for these cases. Intraoperative scans including an RFA probe are very critical in the clinical practice and need a very careful segmentation and inspection to avoid under-treatment, which may result in tumor recurrence (up to 40%). If the decision can be made during the intervention, an additional ablation can be performed without removing the entire needle. This decreases the patient stress and associated risks and costs of a separate intervention at a later date. Ultimately, the segmented ablation zone containing the RFA needle can be used for a precise ablation simulation as the real needle position is known.

关键词： RFA decreases patient stress

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客座编辑序言(英文)

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China Communications 2014年第7期 8-9页

作者：谢高岗 Kave Salamatian 徐明伟谢海永孙毅 Network Technology Research Center at Institute of Computing Technology(ICT) Chinese Academy of Sciences(CAS) University of Savoie the Institute of Computer Networks in Tsinghua University US Innovation Center University of Science and Technology of China the P4P working group of Distributed Computing Industry Association ICT Macquarie University

In recent years,two exciting approaches Software-defined Networking(SDN)and Post-IP architecture(or Future Internet Architecture)to future Internet have been studied all over the world both in industry and *** refactors the relationship between network devices and the software that controls them to separate data plane and control plane and it is regarded as an incremental approach toward the future Internet *** the

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Consumer participation in quality improvements for chronic disease care: Development and evaluation of an interactive patient-centered survey to identify preferred service initiatives

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Journal of Medical Internet Research 2014年第12期16卷 e292页

作者： Fradgley, Elizabeth A. Paul, Christine L. Bryant, Jamie Roos, Ian A. Henskens, Frans A. Paul, David J. Priority Research Centre for Health Behaviour School of Medicine and Public Health Hunter Medical Research Institute University of Newcastle Callaghan 2305 Australia Youth Research Center University of Melbourne Melbourne Australia Distributed Computing Research Group School of Electrical Engineering and Computer Science University of Newcastle Callaghan Australia

Background: With increasing attention given to the quality of chronic disease care, a measurement approach that empowers consumers to participate in improving quality of care and enables health services to systematically introduce patient-centered initiatives is needed. A Web-based survey with complex adaptive questioning and interactive survey items would allow consumers to easily identify and prioritize detailed service initiatives. Objective: The aim was to develop and test a Web-based survey capable of identifying and prioritizing patient-centered initiatives in chronic disease outpatient services. Testing included (1) test-retest reliability, (2) patient-perceived acceptability of the survey content and delivery mode, and (3) average completion time, completion rates, and Flesch-Kincaid reading score. Methods: In Phase I, the Web-based Consumer Preferences Survey was developed based on a structured literature review and iterative feedback from expert groups of service providers and consumers. The touchscreen survey contained 23 general initiatives, 110 specific initiatives available through adaptive questioning, and a relative prioritization exercise. In Phase II, a pilot study was conducted within 4 outpatient clinics to evaluate the reliability properties, patient-perceived acceptability, and feasibility of the survey. Eligible participants were approached to complete the survey while waiting for an appointment or receiving intravenous therapy. The age and gender of nonconsenters was estimated to ascertain consent bias. Participants with a subsequent appointment within 14 days were asked to complete the survey for a second time. Results: A total of 741 of 1042 individuals consented to participate (71.11% consent), 529 of 741 completed all survey content (78.9% completion), and 39 of 68 completed the test-retest component. Substantial or moderate reliability (Cohen's kappa>0.4) was reported for 16 of 20 general initiatives with observed percentage agreement ra

关键词： Ambulatory care Cardiology Chronic disease Consumer participation Health care surveys Medical oncology Neurology Patient-centered care

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The Power of Non-Uniform Wireless Power 13

The Power of Non-Uniform Wireless Power

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Annual ACM-Society for Industrial and Applied Mathmatics Symposium on Discrete Algorithms

作者： Magnus M. Halldorsson Stephan Holzer Pradipta Mitra Roger Wattenhofer ICE-TCS School of Computer Science Reykjavik University Distributed Computing Group

ISBN: (纸本)9781611972511

We study a fundamental measure for wireless interference in the SINR model known as (weighted) inductive independence. This measure characterizes the electiveness of using oblivious power - when the power used by a transmitter only depends on the distance to the receiver - as a mechanism for improving wireless capacity. We prove optimal bounds for inductive independence, implying a number of algorithmic applications. An algorithm is provided that achieves - due to existing lower bounds - capacity that is asymptotically best possible using oblivious power assignments. Improved approximation algorithms are provided for a number of problems for oblivious power and for power control, including distributed scheduling, connectivity, secondary spectrum auctions, and dynamic packet scheduling.

关键词： Wireless Power power assignments packet scheduling power Power Energy sources Power (Psychology) Power packet schedule wireless Approximation algorithms Power control secondary spectrum

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Performance analysis of computational approaches to solve Multiple Sequence Alignment

Performance analysis of computational approaches to solve Mu...

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作者： Montañola, Alberto Roig, Concepció Guirado, Fernando Hernández, Porfidio Notredame, Cedric Distributed Computing Group Computer Science and Industrial Engineering Department Universitat de Lleida Lleida Spain Computer Architecture and Operating Systems Department Universitat Autònoma de Barcelona Cerdanyola del Vallès Spain Barcelona Spain

In the biotechnology field, the deployment of the Multiple Sequence Alignment (MSA) problem, which is a high performance computing demanding process, is one of the new challenges to address on the new parallel systems. The aim of this problem is to find similar regions on biological sequences. Furthermore, the goal of MSA applications is to align as much sequences as possible with a level of quality that makes the alignment biologically meaningful. An efficiency study of different MSA implementations, based on T-Coffee (one of the most used MSA aligners), has been performed in order to find new optimizations that may improve the average execution time on multi-core systems. We found that the current parallel implementations have some performance issues, affecting negatively the scalability of the process. Finally, the proposed implementation based on the usage of threads in conjunction with a message-passing library is presented, with the aim to optimize the execution of the MSA problem in multi-core-based clusters. © 2012 Springer Science+Business Media, LLC.

关键词： Message passing

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Why Eve and Mallory love Android: An analysis of Android SSL (in)security 12

Why Eve and Mallory love Android: An analysis of Android SSL...

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2012 ACM Conference on computer and Communications Security, CCS 2012

作者： Fahl, Sascha Harbach, Marian Muders, Thomas Smith, Matthew Baumgärtner, Lars Freisleben, Bernd Distributed Computing and Security Group Leibniz University of Hannover Hannover Germany Department of Math. and Computer Science Philipps University of Marburg Marburg Germany

ISBN: (纸本)9781450316507

Many Android apps have a legitimate need to communicate over the Internet and are then responsible for protecting potentially sensitive data during transit. This paper seeks to better understand the potential security threats posed by benign Android apps that use the SSL/TLS protocols to protect data they transmit. Since the lack of visual security indicators for SSL/TLS usage and the inadequate use of SSL/TLS can be exploited to launch Man-in-the-Middle (MITM) attacks, an analysis of 13,500 popular free apps downloaded from Google's Play Market is presented. We introduce MalloDroid, a tool to detect potential vulnerability against MITM attacks. Our analysis revealed that 1,074 (8.0%) of the apps examined contain SSL/TLS code that is potentially vulnerable to MITM attacks. Various forms of SSL/TLS misuse were discovered during a further manual audit of 100 selected apps that allowed us to successfully launch MITM attacks against 41 apps and gather a large variety of sensitive data. Furthermore, an online survey was conducted to evaluate users' perceptions of certificate warnings and HTTPS visual security indicators in Android's browser, showing that half of the 754 participating users were not able to correctly judge whether their browser session was protected by SSL/TLS or not. We conclude by considering the implications of these findings and discuss several countermeasures with which these problems could be alleviated. Copyright © 2012 ACM.

关键词： Sensitive data

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distributed verification and hardness of distributed approximation

Distributed verification and hardness of distributed approxi...

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作者： Sarma, Atish Das Holzer, Stephan Kor, Liah Korman, Amos Nanongkai, Danupon Pandurangan, Gopal Peleg, David Wattenhofer, Roger EBay Research Labs EBay Inc. San Jose CA 95125 United States Computer Distributed Computing Group ETH Zurich CH-8092 Zurich Switzerland Department of Computer Science and Applied Mathematics Weizmann Institute of Science Rehovot 76100 Israel CNRS LIAFA Univ. Paris 7 Paris France Theory and Applications of Algorithms Research Group University of Vienna 1090-Vienna Austria Division of Mathematical Sciences Nanyang Technological University Singapore 637371 Singapore Department of Computer Science Brown University Providence RI 02912 United States

We study the verification problem in distributed networks, stated as follows. Let H be a subgraph of a network G where each vertex of G knows which edges incident on it are in H. We would like to verify whether H has some properties, e.g., if it is a tree or if it is connected (every node knows at the end of the process whether H has the specified property or not). We would like to perform this verification in a decentralized fashion via a distributed algorithm. The time complexity of verification is measured as the number of rounds of distributed communication. In this paper we initiate a systematic study of distributed verification and give almost tight lower bounds on the running time of distributed verification algorithms for many fundamental problems such as connectivity, spanning connected subgraph, and s-t cut verification. We then show applications of these results in deriving strong unconditional time lower bounds on the hardness of distributed approximation for many classical optimization problems including minimum spanning tree (MST), shortest paths, and minimum cut. Many of these results are the first nontrivial lower bounds for both exact and approximate distributed computation, and they resolve previous open questions. Moreover, our unconditional lower bound of approximating MST subsumes and improves upon the previous hardness of approximation bound of Elkin [M. Elkin, SIAM J. Comput., 36 (2006), pp. 433-456] as well as the lower bound for (exact) MST computation of Peleg and Rubinovich [D. Peleg and V. Rubinovich, SIAM J. Comput., 30 (2000), pp. 1427-1442]. Our result implies that there can be no distributed approximation algorithm for MST that is significantly faster than the current exact algorithm for any approximation factor. Our lower bound proofs show an interesting connection between communication complexity and distributed computing which turns out to be useful in establishing the time complexity of exact and approximate distributed computatio

关键词： Computational complexity

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