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7th International Conference on Smart and Sustainable Technologies, SpliTech 2022

作者： Jancic, Mitja Strnisa, Filip Kosec, Gregor Parallel and Distributed Systems Laboratory Joief Stefan Institute Joief Stefan International Postgraduate School Ljubljana Slovenia Parallel and Distributed Systems Laboratory Joief Stefan Institute Ljubljana Slovenia

ISBN: (纸本)9789532901160

With the immense computing power at our disposal, the numerical solution of partial differential equations (PDEs) is becoming a day-to-day task for modern computational scientists. However, the complexity of real-life problems is such that tractable solutions do not exist. This makes it difficult to validate the numerically obtained solution, so good error estimation is crucial in such cases. It allows the user to identify problematic areas in the computational domain that may affect the stability and accuracy of the numerical method. Such areas can then be remedied by either h- or p-adaptive procedures. In this paper, we propose to estimate the error of the numerical solution by solving the same governing problem implicitly and explicitly, using a different approximation order in each case. We demonstrate the newly proposed error indicator on the solution of a synthetic two-dimensional Poisson problem with tractable solution for easier validation. We show that the proposed error indicator has good potential for locating areas of high error. © 2022 University of Split, FESB.

关键词： Poisson equation

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Quality of Context 1

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丛书名： Lecture Notes in Computer Science

1000年

作者： Kurt Rothermel Dieter Fritsch Wolfgang Blochinger Frank Dürr

ISBN: (数字)9783642045592

ISBN: (纸本)9783642045585

This book constitutes the thoroughly refereed post-conference proceedings of the first International Workshop on Quality of Context, QuaCon 2009, held in Stuttgart, Germany, in June 2009. The 11 revised papers presented were carefully reviewed and selected from 19 submissions and included in the volume together with 5 invited papers. Discussed are interdisciplinary approaches to context quality, such as models for degradation and consistency of context data, spatial ontologies and spatial data mining, trust in context data, methods and calculi for context quality assessment, frameworks and metrics for context quality, uncertainty in sensor data processing, quality-aware algorithms for context management, quality-aware event and stream processing, uncertainty in reasoning on context data, application-specific context quality and case studies, and visualization of context quality.

关键词： Information Storage and Retrieval User Interfaces and Human Computer Interaction Data Mining and Knowledge Discovery Information systems Applications (incl. Internet) Information systems and Communication Service Computer Communication Networks

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Spatially adaptive refinement

Spatially adaptive refinement

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作者： Pflüger, Dirk Institute for Parallel and Distributed Systems University of Stuttgart 70569 Stuttgart Germany

ISBN: (纸本)9783642317026

While sparse grids allow one to tackle problems in higher dimensionalities than possible for standard grid-based discretizations, real-world applications often come along with requirements or restrictions which enforce problem-dependent adaptations of the standard sparse grid technique. Consider, for example, interpolations where the function values at grid points are obtained via time-consuming numerical simulations. Then, only very few grid points can be spent;classical convergence might be out of reach. Another hurdle is that real-world problems often do not meet the smoothness requirements of the sparse grid method. Thus, the standard approach has to be fine-tuned to the problem at hand, especially in higher-dimensional settings. Therefore, a suitable choice of basis functions can be required, as well as criteria for problem-adapted refinement. Fortunately, and in contrast to full grids, the hierarchical basis formulation of the direct sparse grid approach conveniently provides a reasonable criterion for spatially adaptive refinement practically for free. This can serve as a starting point to develop suitable modifications. We show several problems stemming from different fields of application and demonstrate modifications of the standard sparse grid approach. They enable one to cope with the properties and requirements of the corresponding problem and can serve as examples for similar challenges. © 2013 Springer-Verlag Berlin Heidelberg.

关键词： Computers

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AdAttester: Secure online mobile advertisement attestation using trustzone 15

AdAttester: Secure online mobile advertisement attestation u...

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13th Annual International Conference on Mobile systems, Applications, and Services, MobiSys 2015

作者： Li, Wenhao Li, Haibo Chen, Haibo Xia, Yubin Institute of Parallel and Distributed Systems Shanghai Jiao Tong University China

ISBN: (纸本)9781450334945

Mobile advertisement (ad for short) is a major financial pillar for developers to provide free mobile apps. However, it is frequently thwarted by ad fraud, where rogue code tricks ad providers by forging ad display or user clicks, or both. With the mobile ad market growing drastically (e.g., from $8.76 billion in 2012 to $17.96 billion in 2013), it is vitally important to provide a verifiable mobile ad framework to detect and prevent ad frauds. Unfortunately, this is notoriously hard as mobile ads usually run in an execution environment with a huge TCB. This paper proposes a verifiable mobile ad framework called AdAttester, based on ARM's TrustZone technology. AdAttester provides two novel security primitives, namely unforgeable clicks and verifiable display. The two primitives attest that ad-related operations (e.g., user clicks) are initiated by the end user (instead of a bot) and that the ad is displayed intact and timely. AdAttester leverages the secure world of TrustZone to implement these two primitives to collect proofs, which are piggybacked on ad requests to ad providers for attestation. AdAttester is non-intrusive to mobile users and can be incrementally deployed in existing ad ecosystem. A prototype of AdAttester is implemented for Android running on a Samsung Exynos 4412 board. Evaluation using 182 typical mobile apps with ad frauds shows that AdAttester can accurately distinguish ad fraud from legitimate ad operations, yet incurs small performance overhead and little impact on user experience. Copyright © 2015 ACM.

关键词： Crime

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Optimal predictive code offloading 11

Optimal predictive code offloading

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11th International Conference on Mobile and Ubiquitous systems: Computing, Networking and Services, MobiQuitous 2014

作者： Berg, Florian Dürr, Frank Rothermel, Kurt Institute of Parallel and Distributed Systems University of Stuttgart Stuttgart70569 Germany

ISBN: (纸本)9781631900396

Modern mobile devices like smart phones and tablets are equipped with powerful processing and memory resources, enabling resource-intensive mobile applications such as highend mobile games. The main limitation, however, remains the energy resource. To improve the energy efficiency, code offloading has been proposed, which offloads code to remote servers and transfers the results back to the mobile device. Although several approaches have shown that code offloading improves energy efficiency significantly in general, they largely neglect the adverse effects of network disconnections. Therefore, we have proposed the concept of preemptive code offloading to improve energy efficiency also under link failures. It transmits so-called safe-points between server and mobile device during remote execution, enabling the re-use of partial remote results after link failures. In this paper, we improve our basic preemptive code offloading approach by optimizing the time when to generate and transmit safepoints to minimize the communication overhead and maximize energy efficiency. To find the optimal safe-point schedule, we use a predictive approach that predicts the mobile link quality in order to send safe-points before network disconnections. Moreover, we consider additional deadline constraints for code execution to ensure a minimal responsiveness of offloaded applications despite link failures. Our evaluation results show that energy efficiency can be improved significantly using our predictive offloading approach. Copyright © 2014 ICST.

关键词： Energy efficiency

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Direct visualization of particle-partition of unity data

Direct visualization of particle-partition of unity data

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16th International Workshop on Vision, Modeling and Visualization, VMV 2011

作者： Üffinger, M. Schweitzer, M.A. Sadlo, F. Ertl, T. Germany Institute of Parallel and Distributed Systems Universität Stuttgart Germany

ISBN: (纸本)9783905673852

Direct visualization of higher-order data provides manifold advantages over the traditional approach, which is based on resampling and subsequent visualization by interpolation-based techniques. Most important, it avoids excessive computation and consumption of memory, and prevents artifacts by pixel-accurate visualization at interactive rates. This work addresses particle-partition of unity simulation data, where fields are modeled both using cell-based analytic representations together with enrichment functions centered at individual points. This combination of bases allows for superior simulation convergence rates and is able to capture high field variations with comparably small sets of basis functions. In this paper we propose direct visualization of such data from 2D simulations, providing accurate insight. We additionally visualize solver performance, allowing for more directed simulation design, and exemplify our technique using a GPU-based prototype on crack simulation examples. © The Eurographics Association 2011.

关键词： Visualization

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Hoarding location-based data using clustering

Hoarding location-based data using clustering

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MobiWAC 2006 - 2006 ACM International Workshop on Mobility Management and Wireless Access

作者： Bürklen, Susanne Marrón, Pedro José Rothermel, Kurt Pfahl, Timo Institute of Parallel and Distributed Systems Universitaet Stuttgart 70569 Stuttgart Germany

ISBN: (纸本)159593488X

The proliferation of mobile devices and the fact that high-bandwidth and continuous connectivity is not available everywhere, has led to the creation of hoarding algorithms that attempt to mitigate the problems related with disconnected operation and with the operation in areas where bandwidth is either scarce or expensive. In this paper, we present a hoarding scheme for location-based data in semi-structured information spaces, such as the World Wide Web, which relies on clustering of semantically related data items. We show by means of experimental evaluation that our clustering-based approach outperforms existing hoarding techniques that do not make use of clustering by a factor of more than 2 in terms of hoard cache hit ratio. Copyright 2006 ACM.

关键词： Cluster analysis

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Metrics and Algorithms for Locally Fair and Accurate Classifications using Ensembles

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Datenbank-Spektrum 2022年第1期22卷 23-43页

作者： Lässig, Nico Oppold, Sarah Herschel, Melanie Institute for Parallel and Distributed Systems – Data Engineering University of Stuttgart Universitätsstr. 38 Stuttgart70569 Germany

To obtain accurate predictions of classifiers, model ensembles comprising multiple trained machine learning models are nowadays used. In particular, dynamic model ensembles pick the most accurate model for each query object, by applying the model that performed best on similar data. Dynamic model ensembles may however suffer, similarly to single machine learning models, from bias, which can eventually lead to unfair treatment of certain groups of a general population. To mitigate unfair classification, recent work has thus proposed fair model ensembles, that instead of focusing (solely) on accuracy also optimize global fairness. While such global fairness globally minimizes bias, imbalances may persist in different regions of the data, e.g., caused by some local bias maxima leading to local unfairness. Therefore, we extend our previous work by including a framework that bridges the gap between dynamic model ensembles and fair model ensembles. More precisely, we investigate the problem of devising locally fair and accurate dynamic model ensembles, which ultimately optimize for equal opportunity of similar subjects. We propose a general framework to perform this task and present several algorithms implementing the framework components. In this paper we also present a runtime-efficient framework adaptation that keeps the quality of the results on a similar level. Furthermore, new fairness metrics are presented as well as detailed informations about necessary data preparations. Our evaluation of the framework implementations and metrics shows that our approach outperforms the state-of-the art for different types and degrees of bias present in training data in terms of both local and global fairness, while reaching comparable accuracy. © 2022, The Author(s).

关键词： Dynamic models

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Fretting wear mechanism of GH4169 dovetail joint specimens treated with hybrid laser shock peening

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Tribology International 2025年 209卷

作者： Fang, Xiuyang Wang, Zheng Wahab, Magd Abdel Gong, Jianen Liu, Xiong Liu, Xing Cai, Zhenbing School of Mechanical Engineering Southwest Jiaotong University Chengdu610031 China Tribology Research Institute Key Lab of Advanced Technologies of Materials Southwest Jiaotong University Chengdu610031 China Soete Laboratory Department of Electrical Energy Metals Mechanical Constructions and Systems Faculty of Engineering and Architecture Ghent University Gent9000 Belgium College of Engineering Yuan Ze University Taiwan China Parallel and Distributed Systems Laboratory Jožef Stefan Institute Jamova cesta 39 LjubljanaSI-1000 Slovenia DongFang Electric Machinery Co. LTD Deyang618000 China State Key Laboratory of Advanced Electromagnetic Technology Huazhong University of Science and Technology Hubei Wuhan430074 China

Aero engine blade structure is prone to severe fretting wear under centrifugal forces and vibration loads, resulting in greatly reduced engine service life, which is a typical fretting damage problem. In this paper, without Absorbing layer Nanosecond Laser Shock Peening (wAN-LSP) and without Absorbing layer Nanosecond superimposed Femtosecond hybrid Laser Shock Peening (NF-LSP) are utilized to strengthen the surface of GH4169 dovetail joint specimens, which is a common material for engine blades, to explore its strengthening mechanism and fretting wear evolution law. The findings indicate that the surface roughness of the wAN-LSP specimen rises from 0.28 μm to 1.16 μm. The thermal effects of wAN-LSP lead to the formation of a molten layer roughly 10.97 μm thick on the surface, accompanied by numerous pits, ablation holes, and micro-cracks. In contrast, NF-LSP treatment effectively eliminates the surface oxidation defects made by the thermal effects of wAN-LSP, leading to a slight decrease in surface roughness. Both wAN-LSP and NF-LSP treatments enhance the surface hardness of the specimens, creating a plastic deformation layer roughly 400 μm deep, but the near surface hardness of NF-LSP treated specimen is further improved compared to that of the wAN-LSP specimen. The wear mechanism observed in the GH4169 dovetail joint specimens following wAN-LSP and NF-LSP treatment are identified as abrasive wear and oxidation wear. Initially, as the number of cycles raises, the wear volume of GH4169 specimen treated with wAN-LSP is higher than that of untreated specimen, but subsequently, it becomes lesser than that of the untreated specimen. This phenomenon results from the interplay between the molten layer and hardened layer. In the initial stage of wear, despite the surface strengthening of the wAN-LSP specimen, the presence of molten layer significantly diminishes the fretting wear resistance of the material. As wear progresses, the molten layer is removed, revealing the be

关键词： Abrasion

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A Model for Jellyfish Detritus Decay through Microbial Processing 44

A Model for Jellyfish Detritus Decay through Microbial Proce...

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44th International Convention on Information, Communication and Electronic Technology, MIPRO 2021

作者： Strnisa, Filip Kosec, Gregor 'Jožef Stefan' Institute Parallel and Distributed Systems Laboratory Ljubljana Slovenia

ISBN: (纸本)9789532331011

The decay of jellyfish blooms introduces a significant organic matter source to the local marine environment that has still an unknown impact on the ecosystem. In recent laboratory experiments, authors studied how the introduction of excess organic material affects the coastal pelagic microbiome by introducing Aurelia aurita detritus to jars of seawater. During these experiments they have monitored bacterial abundance, amino acids' concentrations, dissolved organic carbon, as well the build-up of some inorganic nutrients. They have found, that about half of the protein-rich organic matter in jellyfish detritus is almost instantly available to microbes as dissolved organic matter. Based on this experimental data we devised a mathematical model of the jellyfish proteins (amino acids) degradation caused by marine bacteria. The model is built on top of the Monod bacterial growth model and the Luedeking-Piret metabolite production model. In addition, we incorporated the bacterial populations' age to model the lag phase as well as bacterial decay. In this paper, we demonstrate that with the proposed model, we can sufficiently describe the laboratory measurements. Keywords-bacterial growth;Monod model;Luedeking-Piret model;jellyfish © 2021 Croatian Society MIPRO.

关键词： Proteins

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