This paper, the second in a two-part series, presents a new methodology for structural identification and nondestructive evaluation by piezo–impedance transducers. The theoretical development and experimental validation of the underlying lead–zirconium–titanate (PZT)–structure interaction model was presented in the first part. In our newly proposed method, the damage in evaluated on the basis of the equivalent system parameters “identified” by the surface-bonded piezo–impedance transducer. As proof of concept, the proposed method is applied to perform structural identification and damage diagnosis on a representative lab-sized aerospace structural component. It is then extended to identify and monitor a prototype reinforced concrete bridge during a destructive load test. The proposed method was found to be able to successfully identify as well as evaluate damages in both the structures. 相似文献
An impedance-based structural health monitoring technique is presented. By analyzing the in-plane vibration of a thin lead–zirconate–titanate (PZT) patch, the electromechanical impedance of the PZT patch is predicted. The force impedances of a beam and a plate with damage are calculated by Ritz method using polynomial as shape functions. The damage is then identified from the changes of the impedance spectra caused by the appearance of damage. A hybrid evolutionary programming is employed as a global search technique to back-calculate the damage. A specially designed fitness function is proposed, which is able to effectively reduce the inaccuracy in representing the real structure using analytical or numerical models. Experiments are carried out on a beam and a plate to verify the numerical predictions. The results demonstrate that the proposed method is able to effectively and reliably locate and quantify the damage in the beam and the plate. 相似文献
Pepsin‐solubilised collagen from the ribbon jellyfish (Chrysaora sp., morphotype 1) umbrella (JPSC) was isolated and characterised. The yield of collagen varied (9–19%, based on ash‐free dry weight) depending on the amount of pepsin used. Type II collagen was the major component of extracted collagen. The peptide map of JPSC differed from that of standard collagen type II, which indicates their different primary structures. FTIR spectra of JPSC, however, did not differ significantly from those of type II collagen. The Tmax of JPSC was 37.38 °C, which is higher than that of other marine collagens. Glycine was the main amino acid in JPSC (320 residues per 1000 residues), followed by glutamic acid, alanine, proline, aspartic acid and hydroxyproline. The isoelectric point of JPSC was 6.64. These results indicate that this jellyfish species has the potential to be a marine source of type II collagen that can be used in place of land‐based sources. 相似文献
We report on a recycling project in which α-Al2O3 was produced from aluminum cans because no such work has been reported in literature. Heated aluminum cans were mixed with 8.0 M of H2SO4 solution to form an Al2(SO4)3 solution. The Al2(SO4)3 salt was contained in a white semi-liquid solution with excess H2SO4; some unreacted aluminum pieces were also present. The solution was filtered and mixed with ethanol in a ratio of 2:3, to form a white solid of Al2(SO4)3·18H2O. The Al2(SO4)3·18H2O was calcined in an electrical furnace for 3 h at temperatures of 400–1400 °C. The heating and cooling rates were 10 °C/min. XRD was used to investigate the phase changes at different temperatures and XRF was used to determine the elemental composition in the alumina produced. A series of different alumina compositions, made by repeated dehydration and desulfonation of the Al2(SO4)3·18H2O, is reported. All transitional alumina phases produced at low temperatures were converted to α-Al2O3 at high temperatures. The X-ray diffraction results indicated that the α-Al2O3 phase was realized when the calcination temperature was at 1200 °C or higher. 相似文献
The future of green electronics possessing great strength and toughness proves to be a promising area of research in this technologically advanced society. This work develops the first fully bendable and malleable toughened polylactic acid (PLA) green composite by incorporating a multifunctional polyhydroxybutyrate rubber copolymer filler that acts as an effective nucleating agent to accelerate PLA crystallization and performs as a dynamic plasticizer to generate massive polymer chain movement. The resultant biocomposite exhibits a 24‐fold and 15‐fold increment in both elongation and toughness, respectively, while retaining its elastic modulus at >3 GPa. Mechanism studies show the toughening effect is due to an amalgamation of massive shear yielding, crazing, and nanocavitation in the highly dense PLA matrix. Uniquely distinguished from the typical flexible polymer that stretches and recovers, this biocomposite is the first report of PLA that can be “bend, twist, turn, and fold” at room temperature and exhibit excellent mechanical robustness even after a 180° bend, attributes to the highly interconnected polymer network of innumerable nanocavitation complemented with an extensively unified fibrillar bridge. This unique trait certainly opens up a new horizon to future sustainable green electronics development. 相似文献
Poly(methyl methacrylate-co-acrylic acid) [P(MMA-co-AA)] incorporated with 0–9 wt% of trimethoxyvinylsilane (TMVS) has been studied to investigate the effect of TMVS on the adhesion properties of P(MMA-co-AA) nanospheres coated on silicon substrate as well as on the power conversion efficiency (PCE) of silicon solar module coated with the polymer nanospheres. The incorporation of 7 and 9 wt% of TMVS into the copolymer has been found to render the copolymer stronger adhesion to glass substrate than the samples with lower amount of TMVS in them. The coating of the P(MMA-co-AA) nanospheres on the glass surface of solar module increases the light harvesting efficiency by serving as an anti-reflective layer. Solar module coated with an array of P(MMA-co-AA) nanospheres with 7 wt% of TMVS yielded the highest PCE enhancement of 98% under the illumination of an AM1.5 solar simulator. The natural weathering results indicate that the copolymer with 7% of TMVS was able to withstand prolonged natural weathering exposure and remained reasonably effective in PCE enhancement up to 130 days of outdoor exposure. This study demonstrates a cost-effective technique to bind [P(MMA-co-AA)] nanospheres onto the silicon surface of solar module via siloxane linkages and thus increases the PCE of the solar module effectively. The Tg of the copolymer increased linearly from 110.31 to 118.42 °C when 0–9 wt% of TMVS was added into it. Thermogravimetry results indicate that the incorporation of TMVS does not give any significant effect on the Td of the copolymer, which occurs at about 390 °C.
Abstract The purpose of this paper is to give a state‐space characterization of all internally stabilizing finite‐dimensional linear time‐invariant output feedback controllers for a given finite‐dimensional linear time‐invariant plant which ensure that the resulting closed‐loop transfer function is extended strictly positive real(ESPR). All such controllers are parameterized by a fixed linear fractional transformation with an ESPR, stable free parameter. The parameterized controllers have a state dimension not less than that of the open‐loop plant. The development uses only elementarily algebraic ideas beginning with a change of variables, an extended version of Kalman‐Yacubovich‐Popov positive real lemma, and Youla parameterization, thus the proofs given are simple and clear. 相似文献