A new extended LMI-based robust gain scheduled state feedback <Emphasis Type="Italic">H</Emphasis><Subscript>2</Subscript> controller design

This paper proposes an improved robust H ₂ state feedback control synthesis for the Linear Parameter Varying (LPV) systems by attaining the affine quadratic stability. In place of standard H ₂ computation in the literature, a new H ₂ computation based on extended Linear Matrix Inequality (LMI) is improved by means of the slack variable, where it is obtained by separation Lyapunov matrix from system matrix. State feedback H ₂ synthesis is improved for the systems, and is more effective and less conservative than the common ones in the literature. Therefore, the less conservative results are obtained for gain scheduling controller design for LPV systems. The numerical examples are presented to show the superiority of the proposed controller design.     

Numerical solution of second‐order,two‐point boundary value problems using continuous genetic algorithms

Second‐order, two‐point boundary‐value problems are encountered in many engineering applications including the study of beam deflections, heat flow, and various dynamic systems. Two classical numerical techniques are widely used in the engineering community for the solution of such problems; the shooting method and finite difference method. These methods are suited for linear problems. However, when solving the non‐linear problems, these methods require some major modifications that include the use of some root‐finding technique. Furthermore, they require the use of other basic numerical techniques in order to obtain the solution. In this paper, the author introduces a novel method based on continuous genetic algorithms for numerically approximating a solution to this problem. The new method has the following characteristics; first, it does not require any modification while switching from the linear to the non‐linear case; as a result, it is of versatile nature. Second, this approach does not resort to more advanced mathematical tools and is thus easily accepted in the engineering application field. Third, the proposed methodology has an implicit parallel nature which points to its implementation on parallel machines. However, being a variant of the finite difference scheme with truncation error of the order O(h²), the method provides solutions with moderate accuracy. Numerical examples presented in the paper illustrate the applicability and generality of the proposed method. Copyright © 2004 John Wiley & Sons, Ltd.     

Modified diffraction theory of Kirchhoff

The diffraction theory of Kirchhoff is reinterpreted and a new form of a surface diffraction integral is developed by using the axioms of the modified theory of physical optics, which leads to the exact scattered fields by conducting bodies. The new integral is arranged according to the interpretation of Young, and the diffracted waves are expressed in terms of a line integral. The method is applied to the diffraction problem by a semi-infinite edge contour.     

二苯乙烯化合物的提取工艺优化及其酪氨酸酶抑制活性

该研究探讨了桑根来源的三种二苯乙烯化合物(氧化白藜芦醇,白藜芦醇和白藜芦醇苷)的富集提取工艺,并对提取物的抗氧化活性和酪氨酸酶抑制作用进行了研究。结果表明,通过单因素试验和响应面试验确定富集二苯乙烯化合物的最佳条件为：提取时间1h,料液比1:20,乙醇浓度90%,在此条件下,桑根中氧化白藜芦醇,白藜芦醇和白藜芦醇苷的含量分别为2923.59μg/g,32.45μg/g和3.15μg/g,富含三种二苯乙烯化合物提取物的得率为10.23%。并且,提取物表现出极强的DPPH自由基清除能力(IC₅₀=0.063 mg/mL)和ABTS自由基清除能力(IC₅₀=0.008 mg/mL)。此外,提取物比熊果苷表现出更强的酪氨酸酶抑制活性,其酪氨酸酶抑制率IC₅₀(2.514μg/m L)仅约为熊果苷(IC₅₀=15.551μg/m L)的16%。综上,高活性的二苯乙烯化合物提取物具有天然抗氧化剂和美白剂的潜力,在食品、美容与医药领域有很大的应用价值。桑根可作为二苯乙烯化合物的重要天然来源,是值得被开发利用的抗氧...     

Synthesis and characterization of two-armed poly(ɛ-caprolactone) polymers initiated by the Schiff's base complexes of copper(II) and nickel(II)

Two-armed poly(?-caprolactone) (TAPCL) polymers were successfully synthesized via the ring opening polymerization (ROP) of ?-caprolactone (?-CL) using the Schiff's base complexes [Cu(SAEE)₂] (1) and [Ni(SAEE)₂] (2), which have two hydroxyl functional groups, as the two-site initiators and tin(II) 2-ethylhexanoate (Sn(Oct)₂) as the catalyst in bulk at 115 °C. The Schiff's base complexes (1 and 2) were synthesized by utilizing the concentrated template synthesis method starting from salicyl aldehyde, 2-(2-aminoethoxy) ethanol and related metal acetate salts. The synthesized TAPCL polymers were characterized by GPC, FTIR, UV–vis, and electron paramagnetic resonance (EPR). The molecular weights of TAPCL polymers linearly increased with increasing molar ratio of the monomer to the initiator. The results obtained from FTIR, UV–vis, and EPR studies indicated that TAPCL polymers had the Schiff's base complexes at the junction point of PCL arms. The crystallization behavior of TAPCL was studied by using differential scanning calorimetry (DSC) and polarizing optical microscopy (POM). Thermal behavior of TAPCL was also investigated by thermogravimetrical analysis (TGA).     

Investigation of Wear and Corrosion Behaviour of AISI 316 L Stainless Steel Coated By ESD Surface Modification

Protection of Metals and Physical Chemistry of Surfaces - AISI 316 L austenitic stainless steel is widely used in various sectors of the industry (chemical, petro-chemical industry, paper industry,...     

The Journey of Phenolics from the First Spark to Advanced Materials

The emergence, historical and recent developments of phenolic resins are reviewed. The history of the invention of the first man made plastics and a short bibliography of the inventor Leo H. Baekeland is provided. Moreover, the basic chemistry of phenol-formaldehyde resins, as synthesis of resol and novolak, their structures, variations, and curing are discussed. Modification of these resins and molecular designs for specific applications in retro perspective are highlighted. This review also provides a comprehensive account on the development of benzoxazine resins as an alternative to classical phenolics. In addition to the benzoxazine synthesis and their curing mechanism, special monomers and polybenzoxazine precursors as curable thermoplastics are reviewed. Besides classical chemicals, the potential of renewables for phenolic resin production is also highlighted. Finally, the relative advantages and disadvantages of these systems are discussed and their future potentials are presented.