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In order to solve the problems of low population diversity and easy to fall into local optimization of particle swarm optimization (PSO), a two-population comprehensive learning PSO algorithm based on particle permutation (PP-CLPSO) is proposed. According to the convergence characteristic of PSO algorithm and the chaotic idea of Logistic mapping, the PSO population and chaotic population of parallel evolution are designed. Combined with the particle numbering mechanism, the same sign structure and the same position structure of particles in the two-population system are formed, in which the inertia weight of particles is adaptively adjusted according to the fitness value. When the search process falls into local optimization, the particles with poor fitness under the same position structure of the PSO population carry out the particle replacement operation according to the same sign structure between the chaotic population and the chaotic population, which realizes the reasonable scheduling of the resources of the two-population system and increases the diversity of the population. Furthermore, the global exploration and local search are carried out by combining the co-particle learning strategy of two-way search and the local learning strategy of linearly decreasing search step, which improves the accuracy of the algorithm. Nine benchmark functions are selected in the experiment, and the proposed algorithm is compared with four improved particle swarm optimization algorithms and four swarm intelligence algorithms at the same time. The experimental results show that the PP-CLPSO algorithm has better comprehensive performance in terms of solution accuracy and convergence speed.

Technology acquisitions are one of the most common growth strategies for firms. Firms that have made multiple acquisitions in the past are more likely to make new ones. With previous M&A experience, firms are more likely to make acquisitions. The acquisition rate is the total number of acquisitions a firm has made at a given time. In technology acquisition, the acquisition rate affects innovative firm performance. The more frequent acquisitions a firm makes, the less innovative performance will occur. A high acquisition rate negatively affects post-acquisition performance by dominating the attention of decision-makers and overloading the firm. During the process, there needs to be structural integration between the acquirer and the target firm. This study empirically analyzes 380 cases of technology acquisitions of U.S. publicly traded companies from 1990 to 2005. The results show that a high acquisition rate is negatively related to the post-acquisition innovation performance of the acquirer. Although structural integration has no impact on the negative relationship between post-acquisition performance and acquisition rate, considering the acquisition rate when pursuing M&A allows acquiring firms to avoid detrimental consequences. [ABSTRACT FROM AUTHOR]

The non-Newtonian flow past multiple cylinders is widely encountered in engineering applications, such as slurry transport, petroleum drilling, and heat transmission systems using hot kerosene. However, the wake characteristics of non-Newtonian flow past multiple cylinders are far from well understood. This paper reports the numerical results of power-law flow past two side-by-side identical circular cylinders with a various gap ratio (G/D = 1.1–6.0) and a power-law index (n = 0.8–1.5) at a fixed Reynolds number (Re = 100) based on the incoming uniform flow velocity. Six wake patterns are identified, including the single bluff-body regime, deflected regime, in-phase regime, anti-phase regime, and two subclasses of flip-flopping regime (FF1 and FF2 regimes). The hydrodynamic coefficients of two cylinders are sensitive to both the gap ratio and the power-law index. The wake structure evolution is closely related to the wake patterns, and six modes of wake evolution are accordingly observed. Since the apparent viscosity of power-law fluid changes with the shear rate, the distribution of local Reynolds number (ReL) around the cylinder surface varies with the wake pattern. As it goes outward along the normal direction from the cylinder surface, the ReL shows a trend of increasing and then decreasing when n < 1, while the opposite trend is observed when n > 1. [ABSTRACT FROM AUTHOR]

In this paper, a numerical simulation investigation is carried out on the coupled response of the flow-induced vibration (FIV) and flow-induced rotation (FIR) of a circular cylinder attached with a triangular fairing at a low Reynolds number of Re = 100. The primary focus is on the impact of FIR on FIV. The vibration response, hydrodynamic coefficient, vortex shedding mode, and flow field characteristics are examined for the fairings within the vibrational reduced velocity Ur range of 3–16 with shape angle of α = 45°, 60°, and 90°. The results reveal that at low Ur, all the three considered fairings have a good suppression effect on the FIV. Nevertheless, the galloping response emerges as Ur increases when α = 45° and 60°. In contrast, the vibration response of 90° fairing presents a wider lock-in region. The rotatable 2-degree of freedom (2-DoF) fairing has a better performance in the reduction of response amplitude and hydrodynamic coefficients. The 2S (two single vortices) vortex shedding mode mainly occurs in the vortex-induced vibration (VIV) region, while 2S–8S (from two to eight vortices), 2P (two pairs of vortices), 2T (two triplets of vortices), and P + T (a pair of vortices and a triple of vortices) modes emerge in the galloping branch. Moreover, four modes of wake structures are identified according to the variation of recirculation region and the migration of boundary layer separation point. Finally, the reduced regions of drag, lift, and amplitude are highlighted compared to the bare cylinder. [ABSTRACT FROM AUTHOR]

This paper reports the wake flow evolution of power-law flow past three tandem cylinders with identical diameter and spacing at a low incoming Reynolds number of Re = 80. The flow characteristics of power-law fluid with variable power-law index n are examined at spacing ratios of L/D = 3, 5, and 8 (where L is the spacing between the centers of two adjacent cylinders and D is the cylinder diameter). Three combined wake interference regimes are identified, including the overshoot-overshoot, overshoot-alternate reattachment, and alternate reattachment-quasi-co-shedding regimes, which are distinctly illustrated from the dynamic mode decomposition results. The quasi-co-shedding regime mainly occurs between the middle and downstream cylinders (denoted as C2 and C3, respectively) when L/D = 5 and L/D = 8. The switching of wake regime contributes to the sudden changes of hydrodynamic coefficients of the cylinders. Nevertheless, due to the shadowing effect, the drags of C2 and C3 remain to smaller than that of the upstream cylinder (denoted as C1). [ABSTRACT FROM AUTHOR]