Evaluation of electromechanical properties and field concentrations near electrodes in piezoelectric thick films for MEMS mirrors by simulations and tests

We examine the nonlinear electromechanical response of piezoelectric mirrors driven by PZT thick films in a combined numerical and experimental investigation. First, some electromechanical tests were performed to measure the response (displacement versus load, displacement versus electric field) of the PZT thick films on elastic layers. A finite element analysis was then employed to determine the material properties in the PZT thick films using measured data. Next, the mirror tilt angle and electromechanical field concentrations due to electrodes in piezoelectric mirrors under electric fields were analyzed by introducing a model for polarization switching in local areas, and a nonlinear behavior was discussed in detail. The mirrors consisted of four fully or partially poled PZT unimorphs. Test results on the mirror tilt angle versus electric field, which verify the model, were also presented.     

Lubricant-Supplying Properties and Durability of Oil-Impregnated Polymers

Numerical optimization of tribological elements usually demands extended computations. The particle swarm optimization (PSO) method is known for its simple implementation and high efficiency in solving multifactor optimization problems. In this study, several parallel computing schemes using PSO for air foil bearing design are compared. The parallel programming models applied are multicore computing by OpenMP and many-core graphics processing unit (GPU) computing using Compute Unified Device Architecture (CUDA) and OpenACC. The best case was obtained when the OpenMP coding was applied at the algorithm level of optimization. The performance of CUDA was found to be compatible with OpenMP when parallel computing was used to solve the bearing model. Due to excess data communications computing using OpenACC was significantly slower than the other approaches. The parallel computing scheme recommended in this study is independent of PSO, which is applicable to tribological studies requiring global optimization analysis.     

Estimation of Δf of nitro derivatives of benzene and toluene using AM1 and DSC

Abstract

The AM1 molecular orbital method and reduced pressure differential scanning calorimetry(RP-DSC) were applied to nitro derivatives of benzene and toluene for estimating Δ_f(1) and Δ_f(c). The heats of phase change were determined by RP-DSC with moderate accuracy and the combination of the heats and Δ_f(g) estimated by AM1 gave Δ_f in condensed phases which are similar to those found in literatures.     

Dynamic fatigue behavior of cracked piezoelectric ceramics in three-point bending under AC electric fields

This paper describes an experimental and analytical study on the dynamic fatigue behavior of cracked piezoelectric ceramics under AC electric fields. Constant load-rate testing was conducted in three-point bending with the single-edge precracked-beam specimens. The crack was created normal to the poling direction. The effects of AC electric fields and loading-rate on the fracture load were examined. A phenomenological model of domain wall motion was also used in finite element computation, and the energy release rate for the permeable crack model was calculated. The effect of AC electric fields on the critical energy release rate was then examined. The results suggest that (1) the fracture load of PZT ceramics decreases as the load-rate decreases; (2) an overall decrease in the fracture load occurs when testing under AC electric fields; and (3) the critical energy release rate is not very affected by the AC electric fields.     

The Purity and Thermal Stability in Air of Metal-Encapsulating Carbon Nanocapsules (MECNCs)

Rare earth elements (Y, La, Ce, Nd, Gd and Dy) encapsulated by carbon nanocapsules (CNCs) were synthesized and their purity and air oxidation stability were estimated. The purity was estimated as the rare earth carbide content. Gd- and Dy-encapsulating CNCs had higher than 30 wt% and others 15 to 20 wt%. Encapsulated rare earth carbide was oxidized by heating in air at 400°C or higher. This suggested oxidation damage to the graphene capsules of CNCs.     

The effects of different inorganic salts,buffer systems,and desalting of Varthemia crude water extract on DPPH radical scavenging activity

The DPPH radical-scavenging activity of 25 inorganic salts, two buffer systems, and crude water extract of aerial parts of Varthemia (Varthemia iphionoides) before and after resins purification were investigated. Eight of the 25 inorganic salts tested quenched the DPPH radical colour. Na₂S₂O₃ and FeCl₂ showed markedly high DPPH colour-quenching activity, with inhibition of 65.3% and 47.7% respectively, at a concentration of 10 μg/ml. Four salts slightly increased the intensity of DPPH radical colour. The rest of tested salts, acetate buffer, and phosphate buffer at a concentration less than 0.1 mM did not affect DPPH radical colour. The DPPH radical-scavenging activity of BHT and catechol was considerably affected by the concentration of phosphate buffer (pH 7.0), and by acetate buffer (pH 5.0) at concentrations more than 0.01 mM in the case of BHT only. The DPPH radical-scavenging activity of a crude water extract of aerial parts of Varthemia iphionoides was much higher than that of an extract desalted by cation-exchange resin, indicating that iron ions apparently elevated the DPPH radical-scavenging activity of the extract. Therefore, desalting of plant extracts is important in order to obtain the true value of DPPH radical-scavenging activity.     

Development of Broadband Telecommunications System for Railways Using Laser Technology

We developed a high‐speed telecommunication system for use on railways to improve customer service and the efficiency of operator's telecommunications between ground facilities and trains under operation. We built a mobile telecommunication system, capable of achieving a transfer rate of 1 Gbps in theory, by utilizing laser beam communications technology. We carried out a field test using trains in active service, and obtained results in which a transfer rate of approximately 700 Mbps in the TCP layer was achieved between the ground and a train running at a speed of approximately 130 km/h .     

Lightning occurrence characteristics in Japan for 17 years: observation results with lightning location systems of electric power utilities from 1992 to 2008

We summarize the lightning data for 17 years from 1992 to 2008 obtained with lightning location systems of nine electric power utilities in Japan and analyze them. The observed annual number of lightning flashes of which the current is more than 10 kA is 400 000–800 000 and the 50% value of the cumulative distribution of lightning peak currents is about 23 kA in recent times. The variation of lightning occurrence characteristics by areas, seasons, and so on, is clarified. Comparison of the obtained data with those obtained by another lightning location system is also made. The relationship between lightning occurrence and climate is discussed. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.     

Outdoor performance of amorphous silicon and polycrystalline silicon PV modules

The daily watt-hour efficiency (η_Wh) and daily integrated output power (P_Wh) of the a-Si and poly-Si module have been used to examine the performances of both modules on the basis of two years' data accumulated at outdoor conditions. Results from the analysis of experimental data taken under incident solar energy higher than 3.0 kWh/m² per day show that the annual average of η_Wh of the a-Si module is about 95% and 92.5% of its efficiency at STC condition at the first and second year, respectively, while the values are nearly unchanged at about 89% for the poly-Si module. During a one year period, the average P_Wh of the a-Si and poly-Si module was about 60% and 56%, respectively, of their calculated output power at STC condition, so that the P_Wh for each watt-peak (W_p) of the maximum power of a-Si module is about 11% higher than that of the poly-Si module.