Dynamic analysis and system identification of an LCD glass-handling robot driven by a PMSM

In this paper, Hamilton’s principle is employed to derive Lagrange’s equations of an liquid crystal display (LCD) glass-handling robot driven by a permanent magnet synchronous motor (PMSM). The robot has three arms driven by two timing belts. The dynamic formulations can be expressed by one and four independent variables, which are named as the rigid and flexible models, respectively. In order to verify the dynamic formulation is correct, we reduce the flexible model to the rigid one under some assumptions. In this paper, we adopt the real-coded genetic algorithm (RGA) to identify all the parameters of the robot and PMSM simultaneously. It is found that the RGA can identify system parameters which are difficult to be measured in practical problems, for examples, the inductance, stator resistance, motor torque constant, damping coefficient of the motor and timing belts. In numerical simulations, vibrations due to flexibility of the timing belts are investigated for the angular displacements, speeds, accelerations of arms, and the horizontal and vertical displacements of the robot. The angular displacements of the robot arm and the translational positions of the robot end are obtained in the numerical simulations and experimental results. From their comparisons, it is demonstrated that identification results of the dynamic model with four independent variables present the better matching with experimental results of the system.     

Synthesis and characterization of a narrow‐bandgap polymer containing alternating cyclopentadithiophene and diketo‐pyrrolo‐pyrrole units for solar cell applications

We have synthesized a narrow‐bandgap conjugated polymer ( PCTDPP ) containing alternating cyclopentadithiophene (CT) and diketo‐pyrrolo‐pyrrole (DPP) units by Suzuki coupling. This PCTDPP exhibits a low band gap of 1.31 eV and a broad absorption band from 350 to 1000 nm, which allows it to absorb more available photons from sunlight. A bulk heterojunction polymer solar cell incorporating PCTDPP and C₇₀ at a blend ratio of 1:3 exhibited a high short‐circuit current of 10.87 mA/cm² and a power conversion efficiency of 2.27%. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 1669–1675, 2010     

Carbazole‐based conjugated polymers incorporating push/pull organic dyes: Synthesis,characterization, and photovoltaic applications

We have synthesized and characterized two new carbazole‐based conjugated polymers, PCDCN and PCDTA , incorporating two strong light‐absorbing organic dyes. These polymers exhibit relatively low band gaps (～1.5 eV) and broad absorption ranges (from 300 to 700 nm). We fabricated polymer solar cells incorporating these polymers as donors and [6,6]‐phenyl‐C₇₁‐butyric acid methyl ester (PC₇₁BM) as the acceptor. At a blending ratio of 1:4, we obtained power conversion efficiencies, under simulated AM 1.5 (100 mW/cm²) conditions, of 2.31% and 2.47% for the PCDCN ‐ and PCDTA ‐based devices, respectively. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem, 2010     

Synthesis and properties of new aromatic polyamides with redox‐active 2,4‐dimethoxytriphenylamine moieties

A new triphenylamine‐based diamine monomer, 4,4′‐diamino‐2″,4″‐dimethoxytriphenylamine ( 2 ), was synthesized from readily available reagents and was reacted with various aromatic dicarboxylic acids to produce a series of aromatic polyamides ( 4a–h ) containing the redox‐active 2,4‐dimethoxy‐substituted triphenylamine (dimethoxyTPA) unit. All the resulting polyamides were readily soluble in polar organic solvents and could be solution cast into tough and flexible films. These polymers exhibited good thermal stability with glass transition temperatures of 243–289 °C and softening temperatures of 238–280 °C, 10% weight loss temperatures in excess of 470 °C in nitrogen, and char yields higher than 60% at 800 °C in nitrogen. The redox behaviors of the polymers were examined using cyclic voltammetry (CV). All these polyamides showed two reversible oxidation processes in the first CV scan. The polymers also displayed low ionization potentials as a result of their dimethoxyTPA moieties. In addition, the polymers displayed excellent stability of electrochromic characteristics with coloration change from a colorless neutral state to green and blue‐purple oxidized states. These anodically coloring polyamides showed high green coloration efficiency (CE = 329 cm²/C), high contrast of optical transmittance change (ΔT% = 84% at 829 nm), and long‐term redox reversibility. © 2010 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 48: 3392–3401, 2010     

Homogeneous polymer blend microparticles with a tunable refractive index

We show that homogeneous polymer blend microparticles can be prepared in situ from droplets of dilute solution of codissolved polymers. Provided that the droplet of solution is small enough (<10 mum), solvent evaporation is rapid enough to inhibit phase separation. Thus the polymers that are being mixed need not be miscible, which greatly enhances the applicability of the technique. From analysis of two-dimensional Fraunhofer diffraction (angular scattering) patterns, we show that both the real and the imaginary parts of the refractive index can be tuned by adjustment of the relative weight fractions of polymers in solution.     

Polycyclic aromatic compounds via radical cyclizations of benzannulated enyne-allenes derived from Ireland-Claisen rearrangement

A new synthetic sequence involving the use of Ireland-Claisen rearrangement of propargylic acetates to form the corresponding benzannulated enyne-allenes followed by Schmittel cyclization to generate benzofulvene biradicals for radical cyclizations leading to polycyclic aromatic compounds was established. Treatment of 9-fluorenone (8) with the lithium acetylide 9 followed by acetic anhydride produced the propargylic acetate 10. A sequence of reactions occurred after 10 was converted to the corresponding silyl ketene acetal 11. An initial Ireland-Claisen rearrangement produced the benzannulated enyne-allene 12, which then underwent a Schmittel cyclization reaction to generate the benzofulvene biradical 13. A subsequent intramolecular radical-radical coupling then produced the formal Diels-Alder adduct 14, which in turn underwent a prototropic rearrangement to give the silyl ester 15 and, after hydrolysis, the carboxylic acid 16 in 57% overall yield from 10 in a single operation. An intramolecular acylation reaction of 16 produced the ketone 17. The carboxylic acids 24-26 were likewise prepared from the diaryl ketones 18-20, respectively. However, the intramolecular [2 + 2] cycloaddition reaction of the benzannulated enyne-allene 33 having a tert-butyl group at the allenic terminus occurred preferentially, producing the 1H-cyclobut[a]indenyl acetic acid 35 as the predominant product.     

Microwave synthesis of polymer-embedded Pt-Ru catalyst for direct methanol fuel cell

Platinum-ruthenium nanoparticles stabilized within a conductive polymer matrix are prepared using microwave heating. Polypyrrole di(2-ethylhexyl) sulfosuccinate, or PPyDEHS, has been chosen for its known electrical conductivity, thermal stability, and solubility in polar organic solvents. A scalable and quick two-step process is proposed to fabricate alloyed nanoparticles dispersed in PPyDEHS. First a mixture of PPyDEHS and metallic precursors is heated in a microwave under reflux conditions. Then the nanoparticles are extracted by centrifugation. Physical characterization by TEM shows that crystalline and monodisperse alloyed nanoparticles with an average size of 2.8 nm are obtained. Diffraction data show that crystallite size is around 2.0 nm. Methanol electro-oxidation data allow us to propose these novel materials as potential candidates for direct methanol fuel cells (DMFC) application. The observed decrease in sulfur content in the polymer upon incorporation of PtRu nanoparticles may have adversely affected the measured catalytic activity by decreasing the conductivity of PPyDEHS. Higher concentration of polymer leads to lower catalyst activity. Design and synthesis of novel conductive polymers is needed at this point to enhance the catalytic properties of these hybrid materials.     

Activation of Au/TiO2 catalyst for CO oxidation

Changes in a Au/TiO(2) catalyst during the activation process from an as-prepared state, consisting of supported AuO(x)(OH)(4-2x)(-) species, were monitored with X-ray absorption spectroscopy and FTIR spectroscopy, complemented with XPS, microcalorimetry, and TEM characterization. When the catalyst was activated with H(2) pulses at 298 K, there was an induction period when little changes were detected. This was followed by a period of increasing rate of reduction of Au(3+) to Au(0), before the reduction rate decreased until the sample was fully reduced. A similar trend in the activation process was observed if CO pulses at 273 K or a steady flow of CO at about 240 K was used to activate the sample. With both activation procedures, the CO oxidation activity of the catalyst at 195 K increased with the degree of reduction up to 70% reduction, and decreased slightly beyond 80% reduction. The results were consistent with metallic Au being necessary for catalytic activity.     

Thermolysis of benzannulated enyne-carbodiimides. Application in the synthesis of pyrido[1',2':1,2]pyrimido[4,5-b]indoles and related heteroaromatic compounds

Several derivatives of the pyrido[1',2':1,2]pyrimido[4,5-b]indoles 4 and the pyrazino[1',2':1,2]pyrimido[4,5-b]indoles 14 were synthesized by treatment of the benzannulated enyne-isocyanates 8 with the iminophosphoranes 9 and 13, respectively, for the aza-Wittig reaction followed by thermolysis. The reaction presumably proceeds through an initial formation of the corresponding benzannulated enyne-carbodiimides, such as 10, followed by a formal intramolecular hetero Diels-Alder reaction. Surprisingly, when the iminophosphorane 17 was used for condensation with 8, the expected pyrimido[1',6':1,2]pyrimido[4,5-b]indoles 16 were not obtained. Instead, the isomeric pyrimido[6',1':2,3]pyrimido[4,5-b]indoles 21 were isolated. Presumably, an alternative reaction pathway involving an initial [2 + 2] cycloaddition reaction to form 19 followed by ring opening could lead to 20 and, after an intramolecular radical-radical coupling, 21. Treatment of the urea derivatives 24 with dibromotriphenylphosphorane also produced in situ the benzannulated enyne-carbodiimides 25, which on thermolysis gave the isoquinolino[2',1':1,2]pyrimido[4,5-b]indoles 26. Methylation of 4a, 14a, and 26a with methyl iodide occurred exclusively at the site of the indolo nitrogen. The planar geometry of those novel heteroaromatic compounds, resembling many DNA-binding agents, makes them potential candidates as DNA intercalators.     

Additivity and the physical basis of multivalency effects: a thermodynamic investigation of the calcium EDTA interaction

To better understand the origin of multivalency effects in ligand binding, the binding of a series of mono-, bi-, tri- and tetravalent carboxylate ligands to Ca(II) was examined by isothermal titration calorimetry (ITC). The data are inconsistent with an entropic origin of enhanced affinity, but rather show that at least in this instance the multivalency effect is enthalpic in origin. Analysis of binding data using the Jencks model shows the addition of incremental carboxylate "ligands" produces an unfavorable interaction entropy that is more than offset by a strongly favorable interaction enthalpy. The most likely source of this interaction enthalpy is the relief of repulsive Coulombic interactions in the unbound state. The conformational entropy penalty arising from the restriction of flexible dihedrals is negligible, within experimental error. On the other hand, an enthalpic contribution from linker restriction contributes strongly to the overall thermodynamics of ligand binding. Together, these data suggest that enthalpic effects dominate ligand binding, and design strategies should seek to optimize these interactions. The incorporation of unfavorable interactions in the unbound ligand that are relieved during binding provides an important mechanism by which to enhance ligand affinities.