Nonlinear model and system identification of a capacitive dual-backplate MEMS microphone

This paper presents the nonlinear identification of a capacitive dual-backplate microelectromechanical systems (MEMS) microphone. First, a nonlinear lumped element model of the coupled electromechanical microphone dynamics is developed. Nonlinear finite element analyses are performed to verify the accuracy of the lumped linear and cubic stiffnesses of the diaphragm. In order to experimentally extract the system parameters, an approximate solution using the second-order multiple scales method is synthesized for a nonlinear microphone model, subject to an electrical step input. A nonlinear least-squares technique is then implemented to extract system parameters from laser vibrometry data of the diaphragm motion. The results indicate that the theoretical fundamental resonant frequency, damping ratio and nonlinear stiffness parameter agree with the corresponding extracted experimental parameters with 95% confidence interval estimates.     

Cationic polymerization behavior of isobutyl vinyl ether with arenesulfonates as non‐salt‐type latent thermal initiators

Substituted and unsubstituted benzenesulfonic acid cyclohexyl esters (1–7) were synthesized, and their possibility as latent thermal initiators in the cationic polymerization of isobutyl vinyl ether (IBVE) was examined to develop novel non‐salt type latent cationic initiators. Thermal decomposition of cyclohexyl p‐nitrobenzenesulfonate (2) in C₆D₆ at 80°C proceeded to exclusively afford cyclohexene as well as p‐nitrobenzenesulfonic acid. Cationic polymerization of IBVE with 1 mol % of an arenesulfonate (1–6) in bulk was carried out at 40–100°C for 12 h. No polymerization took place below 50°C, while the consumption of IBVE depending on both the polymerization temperature and the structure of the arenesulfonates was observed above 60°C. The obtained polyIBVEs showed bimodal GPC curves in several cases, revealing the intervention of two independent propagation species in the polymerization. The cationic polymerization of IBVE with cyclohexyl 2,4,6‐triisopropylbenzenesulfonate (7) at 80°C confirmed the acceleration effect of bulkiness on the polymerization rate. It was concluded that the polymerization was largely dependent on both electronic and steric factors of the aryl groups of the initiators which were directly related to the stability of the sulfonate anions. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 293–301, 1999     

Synthesis of a poly(vinyl ether) containing a benzocyclobutene moiety and its reaction with dienophiles

1‐Benzocyclobutenyl vinyl ether (1) was easily prepared by the elimination reaction of hydrogen bromide from 1‐benzocyclobutenyl 1‐bromoethyl ether obtained by 1‐bromobenzocyclobutene and ethylene glycol via two steps in a good yield. Cationic polymerizations of 1 was carried out at −78°C for 2 h in toluene in the presence of BF₃OEt₂ as an initiator to give quantitatively the corresponding polymers (2) as white solids. As a model reaction of the polymer reaction of 2 with dienophiles, the Diels–Alder reactions of 1‐methoxybenzocyclobutene with maleic anhydride (MA) in toluene at 100–140°C for 3 h were carried out to obtain the corresponding Diels–Alder adduct quantitatively at 140°C. The polymer reactions of 2 with MA and N‐phenylmaleimide (MI) in toluene were carried out to yield the corresponding Diels–Alder adduct polymers in good yields. The degree of introduction of the dienophile could be controlled by temperature, and the unreacted benzocyclobutene moiety could further react with another benzocyclobutene moiety or dienophile. The properties (solubilities, T_g, and temperature of 10% weight loss) of the polymers obtained from the polymer reaction were quite different from those of 2. © 1999 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 37: 59–67, 1999     

Floating zone growth and high-temperature hardness of CrB2 single crystals

Single crystals of CrB₂ were prepared by the floating zone method. The crystal quality was improved by controlling the molten zone composition. The crystals preferentially grew normal to the plane which has the lowest Vickers hardness, similar to the other refractory boride crystals. On the growth plane, the direction of the a-plane, which longitudinally exists along the crystal rod, was controlled without the seed crystal by the position of the lower sintered rod. The anisotropy in the hardness was also consistent with morphology of the crystals prepared by the flux growth. In addition, the hardness measurement was useful for estimating the quality of refractory crystals in the floating zone growth.     

Total Synthesis of Vancomycin Aglycon—Part 2: Synthesis of Amino Acids 1–3 and Construction of the AB-COD-DOE Ring Skeleton

A triazene-based synthetic strategy for the construction of the complex biaryl ethers and a Suzuki coupling reaction were the key steps in the synthesis of precursor 1 of the aglycon of vancomycin, which already contains the complete skeleton of the target compound. The cleavage of the triazene unit from the D ring and the removal of the other protecting groups led to the aglycon of vancomycin. These strategies should be particularly valuable for the synthesis of other naturally occurring glycopeptide antibiotics and offer opportunities for the synthesis of combinatorial libraries of compounds of the vancomycin family for chemical biology studies.     

Cationic ring-opening copolymerization of seven-membered cyclic sulfite and oxetane in one-shot feeding

Cationic copolymerization of seven-membered cyclic sulfite, 1,3,2-dioxathiepane-2-oxide (1) and oxetane (2) in one-shot feeding was carried out to obtain the corresponding copolymer. When a mixture of equimolar amount of 1 and 2 reacted at 0°C in the presence of methyl trifluoromethanesulfonate (T fOMe) as a cationic initiator, T fOMe and 2 were completely consumed without the consumption of 1. After rising the polymerization temperature up to 25°C, 1 started to be consumed to obtain the corresponding copolymer of 1 and 2. The obtained copolymer showed a unimodal GPC curve, and it afforded a polyether showing a unimodal GPC after alkaline hydrolysis. These results strongly suggested the occurrence of the block copolymerization in one-shot feeding. From the molecular orbital examination, the formation of block copolymerization in one-shot feeding was discussed to be caused by the much larger polymerizability of 2 than that of 1. © 1997 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 35: 1007–1012, 1997     

Polymerization of o-quinodimethanes, 1. Radical polymerization of 1-methoxy-o-quinodimethane formed in situ by thermal isomerization of 1-methoxy-benzocyclobutene

The first radical polymerization of 1-methoxy-o-quinodimethane (2) generated by thermal ring-opening isomerization of 1-methoxybenzocyclobutene (1) is described. The polymerization of 1 in the presence of a radical initiator afforded an MeOH-insoluble polymer (3) in moderate yield at temperatures above 90°C. The structure of the obtained polymer is consistent with a ring-opening polymerization. The yield of the polymer increased with the amount of initiator. Radical copolymerization with methyl acrylate was carried out. Treatment of 3 with acid gave poly(o-phenylenevinylene), quantitatively.     

Synthesis of fully conjugated aromatic polyazomethine from AB-type monomer using soluble precursor method

A new AB-type monomer, N,N-bistrimethylsilylated p-aminobenz-aldehyde diethyl acetal was prepared via three steps from p-bromoaniline as a starting material. The two-stage polymerization involving a soluble precursor polymer process gave a poly(p-phenylenevinylene)-type polyazomethine, poly(1,4-phenylene-nitrilomethylidyne). The first stage of polymerization was carried out in tetrahydrofuran or hexamethylphosphoramide containing water at room temperature. In the second stage, the polymer was thermally converted into the final polyazomethine by heating over 300°C to form a free-standing film. The film was reddish brown and insoluble in common organic solvents. The investigation of the first-stage products by means of MALDI-TOF mass spectroscopy proved the oligomers with 4-11 repeating units per molecule. From the ¹H-NMR analysis of the model reaction, the polymerization mechanism was found to be a stepwise polycondensation of 4-diethoxymethylaniline which was formed by removal of two silyl groups of the monomer.