Explore the vast range of titles available.

The reactive materials filled structure (RMFS) is a structural penetrator that replaces high explosive (HE) with reactive materials, presenting a novel self-distributed initiation, multiple deflagrations behavior during penetrating multi-layered plates, and generating a multipeak overpressure behind the plates. Here analytical models of RMFS self-distributed energy release and equivalent deflagration are developed. The multipeak overpressure formation model based on the single deflagration overpressure expression was promoted. The impact tests of RMFS on multi-layered plates at 584 m/s, 616 m/s, and 819 m/s were performed to validate the analytical model. Further, the influence of a single overpressure peak and time intervals versus impact velocity is discussed. The analysis results indicate that the deflagration happened within 20.68 mm behind the plate, the initial impact velocity and plate thickness are the crucial factors that dominate the self-distributed multipeak overpressure effect. Three formation patterns of multipeak overpressure are proposed. •The space distribution model of equivalent deflagration points of reactive material filled structure (RMFS) is developed.•The analytical model describing the self-distributed deflagration behavior of RMFS is developed.•The formation mechanism of multi-peak overpressure subjected to sequential impact and chemical deflagration is revealed.•Three multipeak overpressure patterns caused by spatiotemporal and multi-source deflagration are discussed.

In this paper, we consider an extended nonlinear Schrödinger equation that includes fifth-order dispersion with matching higher-order nonlinear terms. Via the modified Darboux transformation and Joukowsky transform, we present the superregular breather (SRB), multipeak soliton and hybrid solutions. The latter two modes appear as a result of the higher-order effects and are converted from a SRB one, which cannot exist for the standard NLS equation. These solutions reduce to a small localized perturbation of the background at time zero, which is different from the previous analytical solutions. The corresponding state transition conditions are given analytically. The relationship between modulation instability and state transition is unveiled. Our results will enrich the dynamics of nonlinear waves in a higher-order wave system.

Consider the following nonlinear Schrödinger–Bopp–Podolsky system in R 3 : - ε 2 Δ u + ( V + ϕ ) u = u | u | p - 1 ; a 2 Δ 2 ϕ - Δ ϕ = 4 π u 2 , where a , ε > 0 ; 1 < p < 5 ; V : R 3 → ] 0 , ∞ [ and we want to solve for u , ϕ : R 3 → R . By means of Lyapunov–Schmidt reduction, we show that if K ≥ 2 , z 0 is a strict local minimum of V , V is adequately flat in a neighborhood of z 0 and ε is sufficiently small, then the system has a multipeak cluster solution with K peaks placed at the vertices of a regular convex K -gon centered at z 0 .

Recently, most histogram shifting-based reversible data hiding (RDH) algorithms have considered the impact of textural information on embedding performance, while exploiting pixels with different local complexities. Prioritizing pixels with small local complexities to accommodate secret data decreases the invalid shifting pixels, thereby reducing distortion. However, though effective, the local complexity is not calculated precisely enough, which results in inaccurate texture division and does not considerably reduce distortion. Thus, we employ a novel local complexity calculation and multipeak embedding (MPE) to effectively improve the capacity-distortion performance. Specifically, the host image is first preprocessed by the dot-cross pattern and divided into two subsets. Then the pixel local complexity of each subset is computed by using the spatial correlation of pixels (SCOP) to improve calculation accuracy. Finally, the peak bins to be expanded in the regions with lower local complexity are adaptively selected for embedding with secret data by MPE. To ensure that the authorized operator can securely gain error-free secret data, we design the location index sequences as special keys, which guarantee the algorithm reversibility and enhance the security of the algorithm at the same time. Experimental results show that our algorithm has superior embedding effectiveness compared to some state-of-the-art RDH methods.

Surrogate models are widely used in simulation-based engineering design. The distribution of samples directly determines the quality and efficiency of surrogate models, which has a significant influence on follow-up work. This paper proposes a multipeak parallel adaptive infilling (MPEI) strategy based on expected improvement (EI), which can be divided into two stages: the construction of candidate peak areas and the selection of appropriate candidates at the candidate peak areas. In the first stage, the candidates are divided into the corresponding subspaces in sequence according to the value of EI and the position of each candidate to construct the candidate peak areas. In the second stage, the Gaussian function is used to extract the uncorrelated parent point and the corresponding offspring points in each candidate peak area. Based on these stages, the MPEI strategy selects multiple new samples in spaces with both local optima and areas of large uncertainty interest, which can fully balance global exploration and local exploitation. In addition, the samples selected in each candidate peak area are concise and locally uniform, which can effectively reduce the computational cost. Seven benchmark cases and one engineering problem are used to validate the performance of the MPEI strategy. The results show that the MPEI strategy can efficiently obtain the desired prediction accuracy of surrogate models at a small price of a few samples and confirm the feasibility and robustness of the presented methodology.

In this paper, we study a nonlinear dynamical system of autonomous ordinary differential equations with a small parameter such that two variables and are fast and another one is slow. If we take the limit as , then this becomes a “ degenerate system ” included in the one-parameter family of two-dimensional subsystems of fast motions with the parameter in some interval. It is assumed that in each subsystem there exists a structurally stable limit cycle . In addition, in the complete dynamical system there is some structurally stable periodic orbit that tends to a limit cycle for some as tends to zero. We can define the first return map, or the Poincaré map, on a local cross section in the hyperplane orthogonal to at some point. We prove that the Poincaré map has an invariant manifold for the fixed point corresponding to the periodic orbit on a guaranteed interval over the variable , and the interval length is separated from zero as tends to zero. The proved theorem allows one to formulate some sufficient conditions for the existence and/or absence of multipeak oscillations in the complete dynamical system. As an example of application of the obtained results, we consider some kinetic model of the catalytic reaction of hydrogen oxidation on nickel.

Accurate streamflow measurements are often challenging for extremely shallow rivers within complex bathymetries. In this study, a new version of the fluvial acoustic tomography (FAT) system operated by high-frequency 53-kHz underwater acoustic transducers was used to measure the discharge of a shallow mountainous river. The system was placed under a stringent site condition that was challenging for receiving pure underwater acoustic signals and hence, resulted in low-quality estimates of the river discharge. To overcome this challenge, the shortest path graph method was adopted to capture the desired hydroacoustic data, which can improve the discharge measurements significantly. The results showed that the discharge estimated by the FAT was in very good agreement with that estimated by the rating curve method, suggesting that the FAT was capable of measuring the river discharge for shallow streams when the minimum water depth for a given cross-section was greater than 28 cm. In addition, the findings of this study indicated that under the low-flow condition, the temperature variations during the daytime and nighttime along the acoustic cross-section can play an important role in reducing the signal-to-noise ratio, hence leading to sparse and weak signals of the arrival time, as recorded by the acoustic transducers.