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With the computational resources becoming available, data-driven methods have emerged as powerful means for equation discovery and model construction. Sparse regression methods such as SINDy (Sparse Identification for Nonlinear Dynamical Systems) can be used for developing reduced-order models of nonlinear systems. In this study, the authors examine how SINDy can be used for developing low-dimensional models for airfoil systems, which experience unsteady aerodynamic loads and flutter instabilities. For a system of multiple closely spaced airfoil oscillators, analytical models are not readily available to determine flutter instabilities, and one has to take recourse to experimental and numerical means. In this work, as a starting point, data collected through simulations of unsteady aerodynamics of a single airfoil oscillator system are considered and a reduced-order model is constructed based on this data.
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CSQ System: A System to Support Constrained Skyline Queries on Transportation Networks
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null (Ed.)System call checking is extensively used to protect the operating system kernel from user attacks. However, existing solutions such as Seccomp execute lengthy rule-based checking programs against system calls and their arguments, leading to substantial execution overhead.To minimize checking overhead, this paper proposes Draco, a new architecture that caches system call IDs and argument values after they have been checked and validated. System calls are first looked-up in a special cache and, on a hit, skip all checks. We present both a software and a hardware implementation of Draco. The latter introduces a System Call Lookaside Buffer (SLB) to keep recently-validated system calls, and a System Call Target Buffer to preload the SLB in advance. In our evaluation, we find that the average execution time of macro and micro benchmarks with conventional Seccomp checking is 1.14× and 1.25× higher, respectively, than on an insecure baseline that performs no security checks. With our software Draco, the average execution time reduces to 1.10× and 1.18× higher, respectively, than on the insecure baseline. With our hardware Draco, the execution time is within 1% of the insecure baseline.more » « less
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null (Ed.)Abstract—System call checking is extensively used to protect the operating system kernel from user attacks. However, existing solutions such as Seccomp execute lengthy rule-based checking programs against system calls and their arguments, leading to substantial execution overhead. To minimize checking overhead, this paper proposes Draco, a new architecture that caches system call IDs and argument values after they have been checked and validated. System calls are first looked-up in a special cache and, on a hit, skip all checks. We present both a software and a hardware implementation of Draco. The latter introduces a System Call Lookaside Buffer (SLB) to keep recently-validated system calls, and a System Call Target Buffer to preload the SLB in advance. In our evaluation, we find that the average execution time of macro and micro benchmarks with conventional Seccomp checking is 1.14_ and 1.25_ higher, respectively, than on an insecure baseline that performs no security checks. With our software Draco, the average execution time reduces to 1.10_ and 1.18_ higher, respectively, than on the insecure baseline. With our hardware Draco, the execution time is within 1% of the insecure baseline.more » « less
- Free Publicly Accessible Full Text
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Accepted Manuscript
- Conference Paper:
- https://doi.org/10.1109/ICDE48307.2020.00160
