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See detailSimulation, control and optimisation for the model of ROS management system
Ignatenko, Andrew UL

Presentation (2014, November 06)

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See detailA simulation-based design paradigm for complex cast components
Bordas, Stéphane UL; Conley, James. G.; Moran, Brian et al

in Engineering with Computers (2007), 23(1), 25-37

This paper describes and exercises a new design paradigm for cast components. The methodology integrates foundry process simulation, non-destructive evaluation (NDE), stress analysis and damage tolerance ... [more ▼]

This paper describes and exercises a new design paradigm for cast components. The methodology integrates foundry process simulation, non-destructive evaluation (NDE), stress analysis and damage tolerance simulations into the design process. Foundry process simulation is used to predict an array of porosity-related anomalies. The probability of detection of these anomalies is investigated with a radiographic inspection simulation tool (XRSIM). The likelihood that the predicted array of anomalies will lead to a failure is determined by a fatigue crack growth simulation based on the extended finite element method and therefore does not require meshing nor remeshing as the cracks grow. With this approach, the casting modeling provides initial anomaly information, the stress analysis provides a value for the critical size of an anomaly and the NDE assessment provides a detectability measure. The combination of these tools allows for accept/reject criteria to be determined at the early design stage and enables damage tolerant design philosophies. The methodology is applied to the design of a cast monolithic door used on the Boeing 757 aircraft. [less ▲]

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See detailSimulation-Based Fault Injection as a Verification Oracle for the Engineering of Time-Triggered Ethernet networks
Fejoz, Loïc; Regnier, Bruno; Miramont, Philippe et al

in Proc. Embedded Real-Time Software and Systems (ERTS 2018) (2018, February 02)

TTEthernet (TTE) is considered for use as high-speed backbone in the avionics of next-generation orbital space launchers. Given the key role of communication in launchers, the OEM must acquire a precise ... [more ▼]

TTEthernet (TTE) is considered for use as high-speed backbone in the avionics of next-generation orbital space launchers. Given the key role of communication in launchers, the OEM must acquire a precise understanding of TTE’s functioning and its performances in nominal and error conditions. This holds especially true for the clock synchronization algorithm, the cornerstone of time-triggered communication in TTE, which involves complex distributed algorithms. In this study, we use both an experimental platform and fault-injection on a simulation model to gain quantified insights in these questions. We first describe a fine-grained simulation model of TTE model and discuss how it has been validated against communication traces recorded on the TTE platform. We then present experiments that evaluate the accuracy of the clock synchronization in TTE in the fault-free case as well as considering permanent link failure and transient transmission errors. Finally, we discuss what we have learned during the project in terms of development process and programming language support for complex simulation models used in the design of critical systems. [less ▲]

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See detailSimulation-based Optimisation Of Selective Laser Sintering/Melting Process
Kabore, Brice Wendlassida UL; Peters, Bernhard UL

in Euro PM2019 Congress Proceedings (2019)

In order to adapt Selective Laser Sintering (SLS) and Melting (SLM) to final products and volume production, many scientists have turned to statistical analysis for quality and process stability. Most of ... [more ▼]

In order to adapt Selective Laser Sintering (SLS) and Melting (SLM) to final products and volume production, many scientists have turned to statistical analysis for quality and process stability. Most of which are based on extensive experiments aiming at finding statistical correlations between input parameters such as layer thickness, orientation, scan speed, powder bed temperature, laser power... and resulting strength and residual stress of the manufactured part. However, the rise of computer simulation based on mathematical models allows predictions at a much lower cost. Mathematical modelling of SLS/SLM involves molecular level thermodynamics and thermo-mechanical behaviour of the powder material. In this study, we employ the newly developed Extended Discrete Element Model to reproduce the SLS process including the mechanisms of sintering and the evolution of fracture properties and self-supporting ability. Results show that such microscale model offers high precision and flexibility for finding optimal process parameters. [less ▲]

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See detailSimulation-based optimization using multi-agent technology for efficient and flexible production planning and control in remanufacturing
Groß, Sebastian UL; Gerke, Wolfgang; Plapper, Peter UL

in International Conference on Remanufacturing (ICoR) 2019 (2019, June 25)

Remanufacturing is a process for used products to make them “as good as new or better”. A remanufacturing system typically consists of the processes disassembly, cleaning, inspection, reconditioning ... [more ▼]

Remanufacturing is a process for used products to make them “as good as new or better”. A remanufacturing system typically consists of the processes disassembly, cleaning, inspection, reconditioning reassembly and testing. Due to unknown condition of the used products many challenges occur which are special to the domain of remanufacturing and not know from manufacturing. The resulting stochastic routing of products and material in particular places special demands on the flexibility of the production planning and control (PPC) in remanufacturing systems. In order to enable stochastic routing, Automated Guided Vehicles (AGVs) are used, which also contributes to increasing the complexity of the PPC. Especially the simultaneous scheduling of machines and AGVs has to be addressed in order to enable an optimal remanufacturing process. This paper provides an overview about current research activities in the field of PPC in remanufacturing and scheduling approaches for AGVs. Furthermore, a promising approach to enable the required flexibility of the remanufacturing system and to control the dynamics contained therein is the use of a multi-agent technology. The proposed approach consists of an optimization of the PPC using a multi-agent based simulation. The multi agent-based simulation consists of intelligent agents that negotiate with each other in order to find an optimal solution and achieve high flexibility. [less ▲]

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See detailSimulation-Based Secure Functional Encryption in the Random Oracle Model
Iovino, Vincenzo UL; Żebrowski, Karol

in Progress in Cryptology -- LATINCRYPT 2015 (2015)

One of the main lines of research in functional encryption (FE) has consisted in studying the security notions for FE and their achievability. This study was initiated by [Boneh et al. – TCC’11, O’Neill – ... [more ▼]

One of the main lines of research in functional encryption (FE) has consisted in studying the security notions for FE and their achievability. This study was initiated by [Boneh et al. – TCC’11, O’Neill – ePrint’10] where it was first shown that for FE the indistinguishability-based (IND) security notion is not sufficient in the sense that there are FE schemes that are provably IND-Secure but concretely insecure. For this reason, researchers investigated the achievability of Simulation-based (SIM) security, a stronger notion of security. Unfortunately, the above-mentioned works and others [e.g., Agrawal et al. – CRYPTO’13] have shown strong impossibility results for SIM-Security. One way to overcome these impossibility results was first suggested in the work of Boneh et al. where it was shown how to construct, in the Random Oracle (RO) model, SIM-Secure FE for restricted functionalities and was asked the generalization to more complex functionalities as a challenging problem in the area. Subsequently, [De Caro et al. – CRYPTO’13] proposed a candidate construction of SIM-Secure FE for all circuits in the RO model assuming the existence of an IND-Secure FE scheme for circuits with RO gates. To our knowledge there are no proposed candidate IND-Secure FE schemes for circuits with RO gates and they seem unlikely to exist. We propose the first constructions of SIM-Secure FE schemes in the RO model that overcome the current impossibility results in different settings. We can do that because we resort to the two following models: In the public-key setting we assume a bound on the number of queries but this bound only affects the running-times of our encryption and decryption procedures. We stress that our FE schemes in this model are SIM-Secure and have ciphertexts and tokens of constant-size, whereas in the standard model, the current SIM-Secure FE schemes for general functionalities [De Caro et al., Gorbunov et al. – CRYPTO’12] have ciphertexts and tokens of size growing as the number of queries. In the symmetric-key setting we assume a timestamp on both ciphertexts and tokens. In this model, we provide FE schemes with short ciphertexts and tokens that are SIM-Secure against adversaries asking an unbounded number of queries. Both results also assume the RO model, but not functionalities with RO gates and rely on extractability obfuscation [Boyle et al. – TCC’14] (and other standard primitives) secure only in the standard model. [less ▲]

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See detailSimulations in the Theory of Soft Matter Group
Schilling, Tanja UL

Scientific Conference (2014, January)

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See detailSimulations methods in Condensed Matter Physics
Schilling, Tanja UL

Presentation (2007)

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See detailSimulink Fault Localisation: an Iterative Statistical Debugging Approach
Liu, Bing UL; Lucia, Lucia UL; Nejati, Shiva UL et al

in Software Testing, Verification & Reliability (2016), 26(6), 431-459

Debugging Simulink models presents a significant challenge in the embedded industry. In this work, we propose SimFL, a fault localization approach for Simulink models by combining statistical debugging ... [more ▼]

Debugging Simulink models presents a significant challenge in the embedded industry. In this work, we propose SimFL, a fault localization approach for Simulink models by combining statistical debugging and dynamic model slicing. Simulink models, being visual and hierarchical, have multiple outputs at different hierarchy levels. Given a set of outputs to observe for localizing faults, we generate test execution slices, for each test case and output, of the Simulink model. In order to further improve fault localization accuracy, we propose iSimFL, an iterative fault localization algorithm. At each iteration, iSimFL increases the set of observable outputs by including outputs at lower hierarchy levels, thus increasing the test oracle cost but offsetting it with significantly more precise fault localization. We utilize a heuristic stopping criterion to avoid unnecessary test oracle extension. We evaluate our work on three industrial Simulink models from Delphi Automotive. Our results show that, on average, SimFL ranks faulty blocks in the top 8.9% in the list of suspicious blocks. Further, we show that iSimFL significantly improves this percentage down to 4.4% by requiring engineers to observe only an average of five additional outputs at lower hierarchy levels on top of high-level model outputs. [less ▲]

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See detailSimulink Fault Localization: an Iterative Statistical Debugging Approach
Liu, Bing UL; Lucia, Lucia UL; Nejati, Shiva UL et al

Report (2015)

Debugging Simulink models presents a significant challenge in the embedded industry. In this work, we propose SimFL, a fault localization approach for Simulink models by combining statistical debugging ... [more ▼]

Debugging Simulink models presents a significant challenge in the embedded industry. In this work, we propose SimFL, a fault localization approach for Simulink models by combining statistical debugging and dynamic model slicing. Simulink models, being visual and hierarchical, have multiple outputs at different hierarchy levels. Given a set of outputs to observe for localizing faults, we generate test execution slices, for each test case and output, of the Simulink model. In order to further improve fault localization accuracy, we propose iSimFL, an iterative fault localization algorithm. At each iteration, iSimFL increases the set of observable outputs by including outputs at lower hierarchy levels, thus increasing the test oracle cost but offsetting it with significantly more precise fault localization. We utilize a heuristic stopping criterion to avoid unnecessary test oracle extension. We evaluate our work on three industrial Simulink models from Delphi Automotive. Our results show that, on average, SimFL ranks faulty blocks in the top 8.9% in the list of suspicious blocks. Further, we show that iSimFL significantly improves this percentage down to 4.4% by requiring engineers to observe only an average of five additional outputs at lower hierarchy levels on top of high-level model outputs. [less ▲]

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See detailSimultaneous alignment and dispersion of carbon nanotubes with lyotropic liquid crystals
Lagerwall, Jan UL; Scalia, G.; Haluska, Miroslav et al

in Physica Status Solidi B. Basic Research (2006), 243(13), 3046-3049

We demonstrate that single-wall carbon nanotubes (SWCNTs) can be macroscopically aligned by means of templating in a lyotropic nematic liquid crystal (LC), a self-assembling anisotropic fluid with orienta ... [more ▼]

We demonstrate that single-wall carbon nanotubes (SWCNTs) can be macroscopically aligned by means of templating in a lyotropic nematic liquid crystal (LC), a self-assembling anisotropic fluid with orienta- tional but no translational order. The CNTs spontaneously adopt the alignment of the host, as we verify by means of resonant Raman spectroscopy. The aqueous LC host, based on the surfactant SDS, simultane- ously keeps the nanotubes well dispersed over time scales of months or longer. The LC can be loaded with CNTs to almost the same extent as the standard isotropic 1% surfactant solutions normally used for dispersing CNTs without any optically visible bundling occurring. [less ▲]

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See detailSimultaneous Analysis of Strongly-Coupled Composite Energy Harvester-Circuit Systems Driven by Fluid-Structure Interaction
Zilian, Andreas UL; Ravi, Srivathsan UL

Scientific Conference (2016, July 27)

A specific class of energy harvester devices is investigated, that allow conversion of ambient fluid flow energy to electrical energy via flow-induced vibrations [1] of a piezo-ceramic composite structure ... [more ▼]

A specific class of energy harvester devices is investigated, that allow conversion of ambient fluid flow energy to electrical energy via flow-induced vibrations [1] of a piezo-ceramic composite structure positioned in the flow field. Potentially harmful flow fluctuations are harnessed to provide independent power supply to small electrical devices [2]. Such concept simultaneously involves the interaction of a composite structure and a surrounding fluid, the electric charge accumulated in the piezo-ceramic material and a controlling electrical circuit. In order to predict the efficiency and operational properties of these devices and to increase their robustness and performance, a predictive model of the complex physical system allows systematic computational investigation of the involved phenomena and coupling characteristics. A monolithic approach is proposed that provides simultaneous modelling and analysis of the harvester, which involves surface-coupled fluid-structure interaction, volume-coupled electro mechanics and a controlling energy harvesting circuit for applications in energy harvesting. A three dimensional space-time finite element approximation [3] is used for numerical solution of the weighted residual form of the governing equations of the flow-driven piezoelectric energy-harvesting device. This method enables time-domain investigation of different types of structures (plate, shells) subject to exterior/interior flow with varying cross sections, material compositions, and attached electrical circuits with respect to the electrical power output generated [4]. The space-time finite element model presented incorporates a novel method to enforce equipotentiality on the electrodes covering the piezoelectric patches, making the charge unknowns naturally appear in the formulation [5]. This enables to adapt any type of electrical circuit added to the electromechanical problem. [less ▲]

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See detailSimultaneous Diagonalization of Incomplete Matrices and Applications
Coron, Jean-Sébastien UL; Notarnicola, Luca UL; Wiese, Gabor UL

Scientific journal (in press)

We consider the problem of recovering the entries of diagonal matrices {U_a}_a for a = 1, . . . , t from multiple “incomplete” samples {W_a}_a of the form W_a = P U_a Q, where P and Q are unknown matrices ... [more ▼]

We consider the problem of recovering the entries of diagonal matrices {U_a}_a for a = 1, . . . , t from multiple “incomplete” samples {W_a}_a of the form W_a = P U_a Q, where P and Q are unknown matrices of low rank. We devise practical algorithms for this problem depending on the ranks of P and Q. This problem finds its motivation in cryptanalysis: we show how to significantly improve previous algorithms for solving the approximate common divisor problem and breaking CLT13 cryptographic multilinear maps. [less ▲]

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See detailSimultaneous Estimation of Multi-Relay MIMO Channels
Mehrpouyan, H.; Blostein, S.D.; Ottersten, Björn UL

in IEEE Global Telecommunications Conference (GLOBECOM) (2013)

This paper addresses training-based channel estimation in distributed amplify-and-forward (AF) multi-input multi-output (MIMO) multi-relay networks. To reduce channel estimation overhead and delay, a ... [more ▼]

This paper addresses training-based channel estimation in distributed amplify-and-forward (AF) multi-input multi-output (MIMO) multi-relay networks. To reduce channel estimation overhead and delay, a training algorithm that allows for simultaneous estimation of the entire MIMO cooperative network’s channel parameters at the destination node is proposed. The exact Cram´er- Rao lower bound (CRLB) for the problem is presented in closedform. Channel estimators that are capable of estimating the overall source-relay-destination channel parameters at the destination are also derived. Numerical results show that while reducing delay, the proposed channel estimators are close to the derived CRLB over a wide range of signal-to-noise ratio values and outperform existing channel estimation methods. Finally, extensive simulations demonstrate that the proposed training method and channel estimators can be effectively deployed in combination with cooperative optimization algorithms to significantly enhance the performance of AF relaying MIMO systems in terms of average-bit-error-rate. [less ▲]

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See detailSimultaneous extraction of proteins and metabolites from cells in culture
Sapcariu, Sean UL; Kanashova, Tamara; Weindl, Daniel UL et al

in MethodsX (2014)

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See detailSimultaneous finite element analysis of circuit-integrated piezoelectric energy harvesting from fluid-structure interaction
Ravi, Srivathsan; Zilian, Andreas UL

in Mechanical Systems & Signal Processing (2019), 114

Flow-driven piezoelectric energy harvesting is a strongly coupled multiphysics phenomenon that involves complex three-way interaction between the fluid flow, the electromechanical effect of the ... [more ▼]

Flow-driven piezoelectric energy harvesting is a strongly coupled multiphysics phenomenon that involves complex three-way interaction between the fluid flow, the electromechanical effect of the piezoelectric material mounted on a deformable substrate structure and the controlling electrical circuit. High fidelity computational solution approaches are essential for the analysis of flow-driven energy harvesters in order to capture the main physical aspects of the coupled problem and to accurately predict the power output of a harvester. While there are some phenomenological and numerical models for flow-driven harvesters reported in the literature, a fully three-dimensional strongly coupled model has not yet been developed, especially in the context of flow-driven energy harvesting. The weighted residuals method is applied to establish a mixed integral equation describing the incompressible Newtonian flow, elastic substrate structure, piezoelectric patch, equipotential electrode and attached electric circuit that form the multiphysics fluid-structure interaction problem. A monolithic numerical solution method is derived that provides consistent and simultaneous solution to all physical fields as well as to fluid mesh deformation. The approximate solution is based on a mixed space-time finite element discretization with static condensation of the auxiliary fields. The discontinuous Galerkin method is utilized for integrating the monolithic model in time. The proposed solution scheme is illustrated in the example of a lid driven cavity with a flexible piezoelectric bottom wall, demonstrating quantification of the amount of electrical energy extractable from fluid flow by means of a piezoelectric harvester device. The results indicate that in order to make reliable predictions on the power output under varying operational states, the realization of strong multiphysics coupling is required for the mathematical model as well as the numerical solution scheme to capture the characteristics of flow-driven energy harvesters. [less ▲]

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See detailThe Simultaneous Local Metric Dimension of Graph Families
Barragan-Ramirez, Gabriel; Estrada-Moreno, Alejandro; Ramirez Cruz, Yunior UL et al

in Symmetry (2017), 9(8),

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See detailSimultaneous observation of gravity tide in Juneau, Southeast Alaska with gPhone#32 and L&R G578 gravimeters
Sato, T.; Miura, S.; Ohta, Y. et al

Speeches/Talks (2010)

Detailed reference viewed: 54 (1 UL)