A multi-objective optimization evolutionary algorithm incorporating preference information based on fuzzy logic

A multi-objective optimization evolutionary algorithm incorporating preference information interactively is proposed. A new nine grade evaluation method is used to quantify the linguistic preferences expressed by the decision maker (DM) so as to reduce his/her cognitive overload. When comparing individuals, the classical Pareto dominance relation is commonly used, but it has difficulty in dealing with problems involving large numbers of objectives in which it gives an unmanageable and large set of Pareto optimal solutions. In order to overcome this limitation, a new outranking relation called “strength superior” which is based on the preference information is constructed via a fuzzy inference system to help the algorithm find a few solutions located in the preferred regions, and the graphical user interface is used to realize the interaction between the DM and the algorithm. The computational complexity of the proposed algorithm is analyzed theoretically, and its ability to handle preference information is validated through simulation. The influence of parameters on the performance of the algorithm is discussed and comparisons to another preference guided multi-objective evolutionary algorithm indicate that the proposed algorithm is effective in solving high dimensional optimization problems.     

Direct observation of the evolving metal–support interaction of individual cobalt nanoparticles at the titania and silica interface

Understanding the metal–support interaction (MSI) is crucial to comprehend how the catalyst support affects performance and whether this interaction can be exploited in order to design new catalysts with enhanced properties. Spatially resolved soft X-ray absorption spectroscopy (XAS) in combination with Atomic Force Microscopy (AFM) and Scanning Helium Ion-Milling Microscopy (SHIM) has been applied to visualise and characterise the behaviour of individual cobalt nanoparticles (CoNPs) supported on two-dimensional substrates (SiO_xSi(100) (x < 2) and rutile TiO₂(110)) after undergoing reduction–oxidation–reduction (ROR). The behaviour of the Co species is observed to be strongly dependent on the type of support. For SiO_xSi a weaker MSI between Co and the support allows a complete reduction of CoNPs although they migrate and agglomerate. In contrast, a stronger MSI of CoNPs on TiO₂ leads to only a partial reduction under H₂ at 773 K (as observed from Co L₃-edge XAS data) due to enhanced TiO₂ binding of surface-exposed cobalt. SHIM data revealed that the interaction of the CoNPs is so strong on TiO₂, that they are seen to spread at and below the surface and even to migrate up to ∼40 nm away. These results allow us to better understand deactivation phenomena and additionally demonstrate a new understanding concerning the nature of the MSI for Co/TiO₂ and suggest that there is scope for careful control of the post-synthetic thermal treatment for the tuning of this interaction and ultimately the catalytic performance.

Understanding the metal–support interaction (MSI) is crucial to comprehend how the catalyst support affects performance and whether this interaction can be exploited in order to design new catalysts with enhanced properties.     

Poly(fluoroalkyl acrylate)-bound ruthenium carbene complex: a fluorous and recyclable catalyst for ring-closing olefin metathesis

The synthesis of a fluorous olefin metathesis catalyst derived from the Grubbs second-generation ruthenium carbene complex is described. The air stable fluorous polymer-bound ruthenium carbene complex 1 shows high reactivity in effecting the ring-closing metathesis of a broad spectrum of diene and enyne substrates leading to the formation of di-, tri-, and tetrasubstituted cyclic olefins in minimally fluorous solvent systems (PhCF3/CH2Cl2, 1:9-1:49 v/v). The catalyst can be readily separated from the reaction mixture by fluorous extraction with FC-72 and repeatedly reused. The practical advantage offered by the fluorous catalyst is demonstrated by its sequential use in up to five different metathesis reactions.     

Bézier曲线降多阶逼近的一种方法

文献[1,2]讨论了Bezier曲线一次降多阶逼近问题,得到了很好的结果.文献[1]利用广义逆矩阵得到不保端点插值的降多阶逼近曲线的控制顶点的表达式.但却没有得到带端点任意阶插值条件的降多阶逼近曲线的控制顶点的表达式.文献[2]得到了带端点任意阶插值的降多阶逼近曲线的控制顶点的解析表达式.本文首先给出两Bezier曲线间距离的定义;然后根据降阶曲线与原曲线间的距离最小,分别得到了用矩阵表示的不保端点插值和保端点任意阶插值的降多阶逼近曲线的控制顶点的显示表达式.所给数值例子显示,用本文方法得到的降多阶逼近曲线对原曲线有很好的逼近效果.     

载气密闭循环氧碘化学激光技术模拟实验研究

载气密闭循环氧碘化学激光器技术是一种有望大幅减小氧碘化学激光器体积和降低运行成本的技术,然而至今鲜见相关实验报道。采用超音速喷管加双螺杆真空泵建成了模拟实验装置,并通过测量超音速喷管前后和双螺杆真空泵出入口处的气动参数的方法开展了载气密闭循环氧碘化学激光器的可行性研究和工作稳定性模拟实验研究。模拟实验研究结果证明了该技术的可行性,发现并分析了其光腔压力随双螺杆真空泵转速提高而出现压力拐点的现象,确定了其稳定运行工作条件,为实现载气密闭循环氧碘化学激光器的真正运行和小型化奠定了良好的基础。     

椭圆光波导基模解析解研究

对椭圆光波导进行了严格的求解，得出了模场的精确解析解，导出了模式特征方程，并对基模的特征方程进行了数值求解，得出了不同椭圆度下的β／ｋｏ～Ｖｙ曲线．     

HL—1装置边缘扰动特性研究—静电探针方法

本文针对HL-1托卡马克边缘等离子体扰动特性做了详细的研究。在低频范围内(2πω≤200kHz《ω_(ci)),装置边缘扰动为湍流扰动。孔栏附近悬浮电位扰动的相对量和密度扰动的相对量分别为40％和30％。频率较低时(2πω≤75kHz),扰动的相关性较强;频率较高时(2πω≥125kHz),相关性下降或呈现下降趋势。实验中还发现,在等离子体刮削层的扰动频谱宽度要大于等离子体柱边缘的谱宽度。最后，文中给出了粒子输流Γ随径向的分布，其值约在1.0×10~(16)cm(-8)、s~(-1)量级。由Γ值可心得到扩散系数经为D≈1.2×10~4cm~2·s~(-1),可以同玻姆扩散系数D_Bohm ≈1.0×10~4cm~2·s~(-1)进行量级上的比较。     

Robust reliable control for uncertain switched nonlinear systems with time delay under asynchronous switching

This paper investigates the problem of robust reliable control for a class of switched nonlinear systems with time delay and actuator failures under asynchronous switching. When the switching instants of the controller experience delays with respect to those of the system, a kind of reliable controller design method is proposed, and the dwell time approach is utilized for the stability analysis. Sufficient conditions for the existence of the reliable controller are formulated in terms of a set of LMIs. Then the proposed approach is extended to take into account switched delay systems with Lipschitz nonlinearities and structured uncertainties. Finally, a numerical example is given to illustrate the effectiveness of the proposed method.     

The Plasma Boundary in Low-Parameter Divertor Discharges on the HL-2A Tokamak

Because the last closed flux-surface （LCFS） finally determines the shape of plasma cross-section, and the shaping of plasma is a key issue directly related with lots of the hot subjects of an advanced tokamak（AT） and of a reactor, e. g., the control on the current density, equilibrium, scrapeoff layer（SOL）, aspects of edge particle and energy, high plasma kinetic energy, and of course, the MHD instability suppression, the further studies on the LCFS related subjects, e. g., its determination, flux loss, etc., are still tokamak research. It equilibrium, poloidal needed for present is also important to get precise LCFS-related equilibrium or configuration properties for the controls on an AT and for the understandings on the underlying basic physical issues in a discharge.     

Application of an air-and-moisture-stable diphenylphosphinite cellulose-supported nanopalladium catalyst for a Heck reaction

A diphenylphosphinite cellulose-supported nanopalladium (Cell?COPPh₂-Pd⁰) was conveniently prepared from cellulose and chlorodiphenylphosphine in pyridine, followed by treatment of an ethanol solution of palladium chloride. The prepared catalysis was found to be air- and moisture-stable and have significant catalytic activities in Heck coupling under mild operating conditions. Various phenyl halides were coupled with alkenes in DMF under air, to afford the corresponding products in good yields. Furthermore, the catalyst can be easily recovered by simple filtration and reused for up to six cycles without losing its activity.