A novel method to obtain a real-time control force strategy using genetic algorithms for dynamic systems subjected to external arbitrary excitations

The paper deals with a discrete differential dynamic programming type of problem. It is an optimal control problem where an external disturbance is controlled over the time horizon by a control force constituted with the well-known convolution approach. The paper presents a simple and novel idea to achieve an optimally controlled response when a linear system is subjected to an arbitrary external disturbance. The proposed approach uses the convolution concept and states that if a control method can be established to restore a unit external disturbance, then the convolution integral can be applied to generate an overall control strategy to control the system when it is subjected to an arbitrary external disturbance. In spite of its simplicity, such a strategy has not been encountered in the literature. The only requirement for this method to be useful is to obtain an optimal control strategy to suppress the vibration of the system when it is subjected to unit response disturbance. To accomplish this, a method from classical optimal control theory such as linear quadratic regulator (LQR) that involves solving the Riccati equation of the associated system can be used. However, genetic algorithm (GA) can be adopted as an alternative way to obtain an optimal control strategy against impulse input. As any arbitrary excitation can be divided into impulses, the convolution concept will constitute the overall optimal control strategy for any arbitrary excitation with simply shifting, scaling and summation (or integration) of the GA-optimized control strategy for each impulse of the arbitrary excitation. The proposed method can be used for real time control applications. Once the control strategy for the impulse disturbance is established, the results can then be used at each time step when online control is performed. Computer simulations were carried out to control the response of a quarter-vehicle active suspension system using the proposed method. The obtained results were compared to those of linear quadratic regulator (LQR) and passive suspension applications. The overall results demonstrated the effectiveness of the proposed method for active suspension systems, especially in suppressing the vehicle body displacement when compared to both the LQR based and passive systems. Furthermore, such a control system proves to be simpler requiring less information to process, which is crucial for real-time applications.     

Electrochemical deposition and characterization of SnS thin films

Thin films of SnS were cathodically deposited onto stainless steel substrates from bath containing 0.025 M SnSO₄, 0.25 M KSCN and 0.25 M Na₂SO₄. The mechanism of electrochemical co-deposition of tin and sulphur was investigated by cyclic voltammetry. Analysis of the chronoamperometric current–time transients suggested that, in the potential range −560 to −590 mV vs saturated calomel electrode, the electrodeposition of SnS involved progressive nucleation model. However, at a potential −600 mV, the electrodeposition involved instantaneous nucleation model. The deposits have been characterized by scanning electron microscopy, X-ray diffraction and optical measurements. SnS films were found to be polycrystalline with an optical energy gap of 1.38 eV.     

Coinage metal complexes of N‐heterocyclic carbene bearing nitrile functionalization: Synthesis and photophysical properties

A new series of N‐heterocyclic carbene (NHC) ligand precursors ( 1 and 2 ) with their [Ag(I)(NHC)₂]PF₆ complexes ( 3 and 4 ) and [ClAu(I)(NHC)] complexes ( 5 and 6 ) are reported. Complexes 5 and 6 were synthesized via transmetalation reaction using either 3 or 4 and AuCl(SMe₂) as reactants, respectively. All the synthesized compounds were fully characterized using elemental analyses and Fourier transform infrared, ¹H NMR and ¹³C NMR spectroscopies. In the crystal structures of 3 , 5 and 6 , the Ag(I) and Au(I) ions are in a linear geometry. The entire structure of 3 is stabilized by significant π–π interactions, while the structures of 5 and 6 are stabilized with the presence of aurophilic interactions between the adjacent Au(I) ions as well as CH–π or π–π interactions. From photoluminescence studies, complexes 5 and 6 show dual‐emission characteristics. The higher‐energy fluorescence originates from ¹XLCT mixed with ¹MLCT, while the lower‐energy phosphorescence is ascribed to ³XLCT and ³MLCT with small contribution of ³ILCT, as evidenced by density functional theory (DFT) and time‐dependent DFT calculations of the modelled molecules.     

Synthesis and characterization of chiral di(N-protected-α-amino)diazo-β-diketones from α-diazoketones and imidazolides derived from amino acids

Di(N-protected-α-amino)diazo-β-diketones were prepared by the reaction of activated N-protected-α-amino acids (imidazolides) with α-diazoketones, derived from natural amino acids, in the presence of lithium diisopropylamide in tetrahydrofuran as the solvent at ?78 °C.     

Thermally oxidized aluminum as catalyst-support layer for vertically aligned single-walled carbon nanotube growth using ethanol

Characteristics and role of Al oxide (Al-O) films used as catalyst-support layer for vertical growth of single-walled carbon nanotubes (SWCNTs) were studied. EB-deposited Al films (20 nm) were thermally oxidized at 400 °C (10 min, static air) to produce the most appropriate surface structure of Al-O. Al-O catalyst-support layers were characterized using various analytical measurements, i.e., atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and spectroscopy ellipsometry (SE). The thermally oxidized Al-O has a highly roughened surface, and also has the most suitable surface chemical states compared to other type of Al-O support layers. We suggest that the surface of thermally oxidized Al-O characterized in this work enhanced Co catalyst activity to promote the vertically aligned SWCNT growth.     

Solid-state electrochemical synthesis of ammonia: a review

Ammonia is one of the most produced chemicals worldwide, and it is not only a major end product but also an important energy storage intermediate. The solid-state electrochemical synthesis of ammonia has the promise to overcome the limitations of the conventional catalytic reactors such as the limited conversion, severe environmental pollution and high energy consumption. Solid-state electrolytes either protonic or oxide ion conductors have been reviewed and particular emphasis is placed on their application to synthesise ammonia. The highest rate of ammonia formation according to the type of electrolyte utilised were in the following order; solid polymers > Ce_0.8Gd_0.2O_2−δ-(Ca₃(PO₄)₂-K₃PO₄) composites > fluorites > perovskites > pyrochlores although the catalysts in electrodes also play an important role. The highest rate reported so far is found to be 1.13 × 10⁻⁸ mol s⁻¹ cm⁻² at 80 °C with a potential of 2 V using Nafion membrane, SmFe_0.7Cu_0.1Ni_0.2O₃ (SFCN), and Ni-Ce_0.8Sm_0.2O_2−δ as solid electrolyte, cathode and anode, respectively. Synthesising ammonia from steam and N₂, by-passing H₂ stage offers many advantages such as reduction of device numbers and then the overall costs. The factors affecting the rate of ammonia formation have been discussed as well.     

Development and validation of a RP‐HPLC method for the quantitation of tofacitinib in rat plasma and its application to a pharmacokinetic study

A novel, simple, specific, sensitive and reproducible high‐performance liquid chromatography (HPLC) assay method has been developed and validated for the estimation of tofacitinib in rat plasma. The bioanalytical procedure involves extraction of tofacitinib and itraconazole (internal standard, IS) from rat plasma with a simple liquid–liquid extraction process. The chromatographic analysis was performed on a Waters Alliance system using a gradient mobile phase conditions at a flow rate of 1.0 mL/min and C₁₈ column maintained at 40 ± 1 °C. The eluate was monitored using an UV detector set at 287 nm. Tofacitinib and IS eluted at 6.5 and 8.3 min, respectively and the total run time was 10 min. Method validation was performed as per US Food and Drug Administration guidelines and the results met the acceptance criteria. The calibration curve was linear over a concentration range of 182–5035 ng/mL (r² = 0.995). The intra‐ and inter‐day precisions were in the range of 1.41–11.2 and 3.66–8.81%, respectively, in rat plasma. The validated HPLC method was successfully applied to a pharmacokinetic study in rats. Copyright © 2015 John Wiley & Sons, Ltd.