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Journal of Optimization Theory and Applications - This paper considers an optimal control problem governed by nonlinear fractional-order systems with multiple time-varying delays and subject to...  相似文献   
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As we progress towards employing self‐propelled micro‐/nanomotors in envisioned applications such as cargo delivery, environmental remediation, and therapeutic treatments, precise control of the micro‐/nanomotors direction and their speed is essential. In this Review, major emerging approaches utilized for the motion control of micro‐/nanomotors have been discussed, together with the lastest publications describing these approaches. Future studies could incorporate investigations on micro‐/nanomotors motion control in a real‐world environment in which matrix complexity might disrupt successful manipulation of these small‐scale devices.  相似文献   
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This paper presents lattice Boltzmann Bhatnagar–Gross–Krook (LBGK) model and incompressible LBGK model‐based lattice Boltzmann flux solvers (LBFS) for simulation of incompressible flows. LBFS applies the finite volume method to directly discretize the governing differential equations recovered by lattice Boltzmann equations. The fluxes of LBFS at each cell interface are evaluated by local reconstruction of lattice Boltzmann solution. Because LBFS is applied locally at each cell interface independently, it removes the major drawbacks of conventional lattice Boltzmann method such as lattice uniformity, coupling between mesh spacing, and time interval. With LBGK and incompressible LBGK models, LBFS are examined by simulating decaying vortex flow, polar cavity flow, plane Poiseuille flow, Womersley flow, and double shear flows. The obtained numerical results show that both the LBGK and incompressible LBGK‐based LBFS have the second order of accuracy and high computational efficiency on nonuniform grids. Furthermore, LBFS with both LBGK models are also stable for the double shear flows at a high Reynolds number of 105. However, for the pressure‐driven plane Poiseuille flow, when the pressure gradient is increased, the relative error associated with LBGK model grows faster than that associated with incompressible LBGK model. It seems that the incompressible LBGK‐based LBFS is more suitable for simulating incompressible flows with large pressure gradients. Copyright © 2014 John Wiley & Sons, Ltd.  相似文献   
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Nanopolystyrene was used as a solid support for the covalent immobilization of Candida antarctica lipase B (CalB) using the photoreactive reagent 1-fluoro-2-nitro-4-azido benzene (FNAB) as a coupling reagent. The obtained derivative was then used as a biocatalyst in a microwave assisted esterification experiment. Factors such as contact time, pH, and enzyme concentration were investigated during immobilization. The hydrolytic activity, thermal, and operational stability of immobilized-CalB were determined. The maximum immobilized yield (218 μg/mg support) obtained at pH 6.8 exhibited optimum hydrolytic activity (4.42 × 103 mU p-nitrophenol/min). The thermal stability of CalB improved significantly when it was immobilized at pH 10, however, the immobilized yield was very low (93.6 μg/mg support). The immobilized-CalB prepared at pH 6.8 and pH 10 retained 50% of its initial activity after incubation periods of 14 and 16 h, respectively, at 60 ℃. The operational stability was investigated for the microwave assisted esterification of oleic acid with methanol. Immobilized-CalB retained 50% of its initial activity after 15 batch cycles in the microwave-assisted esterification. The esterification time was notably reduced under microwave irradiation. The combined use of a biocatalyst and microwave heating is thus an alternative total green synthesis process.  相似文献   
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Surface organic ligands play a critical role in stabilizing atomically precise metal nanoclusters in solutions. However, it is still challenging to prepare highly robust ligated metal nanoclusters that are surface‐active for liquid‐phase catalysis without any pre‐treatment. Now, an N‐heterocyclic carbene‐stabilized Au25 nanocluster with high thermal and air stabilities is presented as a homogenous catalyst for cycloisomerization of alkynyl amines to indoles. The nanocluster, characterized as [Au25(iPr2‐bimy)10Br7]2+ (iPr2‐bimy=1,3‐diisopropylbenzimidazolin‐2‐ylidene) ( 1 ), was synthesized by direct reduction of AuSMe2Cl and iPr2‐bimyAuBr with NaBH4 in one pot. X‐ray crystallization analysis revealed that the cluster comprises two centered Au13 icosahedra sharing a vertex. Cluster 1 is highly stable and can survive in solution at 80 °C for 12 h, which is superior to Au25 nanoclusters passivated with phosphines or thiols. DFT computations reveal the origins of both electronic and thermal stability of 1 and point to the probable catalytic sites. This work provides new insights into the bonding capability of N‐heterocyclic carbene to Au in a cluster, and offers an opportunity to probe the catalytic mechanism at the atomic level.  相似文献   
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