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31.
Comparison of the identification performance of conventional FEM updating and integrated DIC 下载免费PDF全文
Andre P. Ruybalid Johan P. M. Hoefnagels Olaf van der Sluis Marc G. D. Geers 《International journal for numerical methods in engineering》2016,106(4):298-320
Full‐field identification methods are increasingly used to adequately identify constitutive parameters to describe the mechanical behavior of materials. This paper investigates the more recently introduced one‐step method of integrated digital image correlation (IDIC) with respect to the most commonly used two‐step method of finite element model updating (FEMU), which uses a subset‐based DIC algorithm. To make the comparison as objective as possible, both methods are implemented in the most equivalent manner and use the same FE model. Various virtual test cases are studied to assess the performance of both methods when subjected to different error sources: (1) systematic errors, (2) poor initial guesses for the constitutive parameters, (3) image noise, (4) constitutive model errors, and (5) experimental errors. Results show that, despite the mathematical similarity of both methods, IDIC produces less erroneous and more reliable results than FEMU, particularly for more challenging test cases exhibiting small displacements, complex kinematics, misalignment of the specimen, and image noise. Copyright © 2015 John Wiley & Sons, Ltd. 相似文献
32.
Igor Solodov Markus Rahammer Nikolai Gulnizkij Marc Kreutzbruck 《Journal of Nondestructive Evaluation》2016,35(3):48
A selective acoustic activation of defects based on the concept of local defect resonance enables to enhance considerably the intensity of defect vibrations and makes it possible to reduce the input acoustic powers to the levels permissible for noncontact nondestructive inspection. Since for cm-size defects in composite materials, the LDR frequencies lie in the low kHz-range, the resonant noncontact activation shifts to an audible frequency range and can be provided by conventional sonic equipment. In this paper, the feasibility of the resonant noncontact inspection is validated for the most “problematic” methodologies of nonlinear, thermosonic and shearosonic NDE that usually require an elevated acoustic power and, therefore, a reliable contact between the specimen and the transducer. In contrast, the noncontact versions developed employ commercial loudspeakers which can simultaneously insonify large areas and be applied for a contactless sonic inspection of different materials and various scale components. 相似文献
33.
Gian Luigi Angrisani Piriya Taptimthong Susanne Elisabeth Thürer Christian Klose Hans Jürgen Maier Marc Christopher Wurz Kai Möhwald 《Advanced Engineering Materials》2018,20(9)
34.
Marc Karle Johannes W?hrle Junichi Miwa Nils Paust G��nter Roth Roland Zengerle Felix von Stetten 《Microfluidics and nanofluidics》2011,10(4):935-939
We demonstrate controlled transport of superparamagnetic beads in the opposite direction of a laminar flow. A permanent magnet
assembles 200 nm magnetic particles into about 200 μm long bead chains that are aligned in parallel to the magnetic field
lines. Due to a magnetic field gradient, the bead chains are attracted towards the wall of a microfluidic channel. A rotation
of the permanent magnet results in a rotation of the bead chains in the opposite direction to the magnet. Due to friction
on the surface, the bead chains roll along the channel wall, even in counter-flow direction, up to at a maximum counter-flow
velocity of 8 mm s−1. Based on this approach, magnetic beads can be accurately manoeuvred within microfluidic channels. This counter-flow motion
can be efficiently be used in Lab-on-a-Chip systems, e.g. for implementing washing steps in DNA purification. 相似文献
35.
Malte Krack Marc Secanell Pierre Mertiny 《Structural and Multidisciplinary Optimization》2011,44(1):57-73
A procedure to find the optimal design of a flywheel with a split-type hub is presented. Since cost plays a decisive role
in stationary flywheel energy storage applications, a trade-off between energy and cost is required. Applying a scaling technique,
the multi-objective design problem is reduced to the maximization of the energy-per-cost ratio as the single objective. Both
an analytical and a finite element model were studied. The latter was found to be more than three orders of magnitude more
computationally expensive than the analytical model, while the analytical model can only be regarded as a coarse approximation.
Multifidelity approaches were examined to reduce the computational expense while retaining the high accuracy and large modeling
depth of the finite element model. Using a surrogate-based optimization strategy, the computational cost was reduced to only
one third in comparison to using only the finite element model. A nonlinear interior-point method was employed to find the
optimal rim thicknesses and rotational speed. The benefits of the split-type hub architecture were demonstrated. 相似文献
36.
Aurélien Bellet Author Vitae Marc Bernard Author Vitae Thierry Murgue Author Vitae Marc Sebban Author Vitae 《Pattern recognition》2010,43(6):2330-2339
During the past few years, several works have been done to derive string kernels from probability distributions. For instance, the Fisher kernel uses a generative model M (e.g. a hidden Markov model) and compares two strings according to how they are generated by M. On the other hand, the marginalized kernels allow the computation of the joint similarity between two instances by summing conditional probabilities. In this paper, we adapt this approach to edit distance-based conditional distributions and we present a way to learn a new string edit kernel. We show that the practical computation of such a kernel between two strings x and x′ built from an alphabet Σ requires (i) to learn edit probabilities in the form of the parameters of a stochastic state machine and (ii) to calculate an infinite sum over Σ* by resorting to the intersection of probabilistic automata as done for rational kernels. We show on a handwritten character recognition task that our new kernel outperforms not only the state of the art string kernels and string edit kernels but also the standard edit distance used by a neighborhood-based classifier. 相似文献
37.
The SHARC framework for data quality in Web archiving 总被引:1,自引:0,他引:1
Dimitar Denev Arturas Mazeika Marc Spaniol Gerhard Weikum 《The VLDB Journal The International Journal on Very Large Data Bases》2011,20(2):183-207
Web archives preserve the history of born-digital content and offer great potential for sociologists, business analysts, and legal experts on intellectual property and compliance issues. Data quality is crucial for these purposes. Ideally, crawlers should gather coherent captures of entire Web sites, but the politeness etiquette and completeness requirement mandate very slow, long-duration crawling while Web sites undergo changes. This paper presents the SHARC framework for assessing the data quality in Web archives and for tuning capturing strategies toward better quality with given resources. We define data quality measures, characterize their properties, and develop a suite of quality-conscious scheduling strategies for archive crawling. Our framework includes single-visit and visit?Crevisit crawls. Single-visit crawls download every page of a site exactly once in an order that aims to minimize the ??blur?? in capturing the site. Visit?Crevisit strategies revisit pages after their initial downloads to check for intermediate changes. The revisiting order aims to maximize the ??coherence?? of the site capture(number pages that did not change during the capture). The quality notions of blur and coherence are formalized in the paper. Blur is a stochastic notion that reflects the expected number of page changes that a time-travel access to a site capture would accidentally see, instead of the ideal view of a instantaneously captured, ??sharp?? site. Coherence is a deterministic quality measure that counts the number of unchanged and thus coherently captured pages in a site snapshot. Strategies that aim to either minimize blur or maximize coherence are based on prior knowledge of or predictions for the change rates of individual pages. Our framework includes fairly accurate classifiers for change predictions. All strategies are fully implemented in a testbed and shown to be effective by experiments with both synthetically generated sites and a periodic crawl series for different Web sites. 相似文献
38.
Bas van der Raadt Author Vitae Marc Bonnet Author Vitae 《Journal of Systems and Software》2010,83(10):1954-1969
Enterprise Architecture (EA) is increasingly being used by large organizations to get a grip on the complexity of their business processes, information systems and technical infrastructure. Although seen as an important instrument to help solve major organizational problems, effectively applying EA seems no easy task. Active participation of EA stakeholders is one of the main critical success factors for EA. This participation depends on the degree in which EA helps stakeholders achieve their individual goals. A highly related topic is effectiveness of EA, the degree in which EA helps to achieve the collective goals of the organization. In this article we present our work regarding EA stakeholder satisfaction and EA effectiveness, and compare these two topics. We found that, regarding EA, the individual goals of stakeholders map quite well onto the collective goals of the organization. In a case study we conducted, we found that the organization is primarily concerned with the final results of EA, while individual stakeholders also worry about the way the architects operate. 相似文献
39.
40.
Adrià Junyent-Ferré Oriol Gomis-Bellmunt Andreas Sumper Marc Sala Montserrat Mata 《Simulation Modelling Practice and Theory》2010,18(9):1365-1381
The present paper deals with the modeling of wind turbine generation systems. The model of a doubly fed induction generator, along with the corresponding converter, crow bar protection and electrical grid is described. The different level control strategies both in normal operation and under voltage dig conditions are discussed, including speed control, torque and reactive power control for the rotor-side converter, reactive and DC voltage control for the grid-side converter and the corresponding current loops control. The results obtained with simulations are compared to experimental data obtained from voltage sags provoked to real wind turbines. 相似文献