1,521 research outputs found
Online Correction of the Dynamic Errors in a Stored Overpressure Measurement System
The problem encountered in sharp shock testing as a result of inadequate bandwidth must be addressed to obtain an accurate overpressure peak value when measuring the steep signals of shockwaves during explosions. A dynamic compensator can effectively amend the dynamic errors caused by sensor system characteristics; thus, a dynamic compensation method based on improved particle swarm optimization (PSO) algorithm is proposed in this paper. This method can effectively overcome the influence of the initial value derived with PSO algorithm on compensator index. The distributed algorithm is introduced into the hardware structure design of the dynamic compensator to facilitate the application of an optimized compensator to real-time online measurement. This integration realizes the high-speed parallel of the dynamic compensator of the sensor with field-programmable gate array. Experimental results show that a high-speed parallel dynamic compensator can amend the dynamic errors in a sensor accurately and in a timely manner
A Tight Deterministic Algorithm for the Submodular Multiple Knapsack Problem
Submodular function maximization has been a central topic in the theoretical
computer science community over the last decade. Plenty of well-performing
approximation algorithms have been designed for the maximization of (monotone
or non-monotone) submodular functions over a variety of constraints. In this
paper, we consider the submodular multiple knapsack problem (SMKP), which is
the submodular version of the well-studied multiple knapsack problem (MKP).
Roughly speaking, the problem asks to maximize a monotone submodular function
over multiple bins (knapsacks). Recently, Fairstein et al. (ESA20) presented a
tight -approximation randomized algorithm for SMKP. Their
algorithm is based on the continuous greedy technique which inherently involves
randomness. However, the deterministic algorithm of this problem has not been
understood very well previously. In this paper, we present a tight
deterministic algorithm for SMKP. Our algorithm is based on
reducing SMKP to an exponential-size submodular maximizaion problem over a
special partition matroid which enjoys a tight deterministic algorithm. We
develop several techniques to mimic the algorithm, leading to a tight
deterministic approximation for SMKP
Simple Deterministic Approximation for Submodular Multiple Knapsack Problem
Submodular maximization has been a central topic in theoretical computer science and combinatorial optimization over the last decades. Plenty of well-performed approximation algorithms have been designed for the problem over a variety of constraints. In this paper, we consider the submodular multiple knapsack problem (SMKP). In SMKP, the profits of each subset of elements are specified by a monotone submodular function. The goal is to find a feasible packing of elements over multiple bins (knapsacks) to maximize the profit. Recently, Fairstein et al. [ESA20] proposed a nearly optimal (1-e^{-1}-?)-approximation algorithm for SMKP. Their algorithm is obtained by combining configuration LP, a grouping technique for bin packing, and the continuous greedy algorithm for submodular maximization. As a result, the algorithm is somewhat sophisticated and inherently randomized. In this paper, we present an arguably simple deterministic combinatorial algorithm for SMKP, which achieves a (1-e^{-1}-?)-approximation ratio. Our algorithm is based on very different ideas compared with Fairstein et al. [ESA20]
Improved Deterministic Algorithms for Non-monotone Submodular Maximization
Submodular maximization is one of the central topics in combinatorial
optimization. It has found numerous applications in the real world. In the past
decades, a series of algorithms have been proposed for this problem. However,
most of the state-of-the-art algorithms are randomized. There remain
non-negligible gaps with respect to approximation ratios between deterministic
and randomized algorithms in submodular maximization.
In this paper, we propose deterministic algorithms with improved
approximation ratios for non-monotone submodular maximization. Specifically,
for the matroid constraint, we provide a deterministic
approximation algorithm, while the previous best deterministic algorithm only
achieves a approximation ratio. For the knapsack constraint, we provide a
deterministic approximation algorithm, while the previous best
deterministic algorithm only achieves a approximation ratio. For the
linear packing constraints with large widths, we provide a deterministic
approximation algorithm. To the best of our knowledge, there is
currently no deterministic approximation algorithm for the constraints.Comment: 25 pages; added a new result about the linear packing constraint
Exploring the characteristics of issue-related behaviors in GitHub using visualization techniques
Bifurcation Study of Thin Plate with an All-Over Breathing Crack
An all-over breathing crack on the plate surface having arbitrary depth and location is assumed to be nonpropagating and parallel to one side of the plate. Based on a piecewise model, the nonlinear dynamic behaviors of thin plate with the all-over breathing crack are studied to analyze the effect of external excitation amplitudes and frequencies on cracked plate with different crack parameters (crack depth and crack location). Firstly, the mode shape functions of cracked thin plate are obtained by using the simply supported boundary conditions and the boundary conditions along the crack line. Then, natural frequencies and mode functions of the cracked plate are calculated, which are assessed with FEM results. The stress functions of thin plate with large deflection are obtained by the equations of compatibility in the status of opening and closing of crack, respectively. To compare with the effect of breathing crack on the plate, the nonlinear dynamic responses of open-crack plate and intact plate are analyzed too. Lastly, the waveforms, bifurcation diagrams, and phase portraits of the model are gained by the Runge-Kutta method. It is found that complex nonlinear dynamic behaviors, such as quasi-periodic motion, bifurcation, and chaotic motion, appear in the breathing crack plate
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