Numerical characterization and experimental verification of an in-plane MEMS-actuator with thin-film aluminum heater

In this paper, a novel concept of a thermo-mechanical MEMS actuator using aluminum thin-film heaters on a thermal oxide for electrical insulation is presented. The actuator is part of an universal tensile testing platform for thermo-mechanical material characterization of one dimensional materials on a micro- and nano-scopic scale under different environmental conditions, as varying temperatures, pressure, moisture or even vacuum and is realised in BDRIE technology. It is shown, that the actuator concept fulfills the requirements for the use in a tensile loading stage along with heterogeneously integrated nanofunctional elements, following a specimen centered approach in line with bottom-up self-assembly processes. Simulation and experiment agree very well in the thermal and mechanical domain and allow subsequent optimisation of the actuator performance.     

Impoverishment of YOY‐fish assemblages by intense commercial navigation in a large Lowland river

Navigation‐induced physical forces have been suggested to modify the structure of riverine fish assemblages by impeding especially the recruitment of littoral bound species. To investigate the effect of vessel frequency on fish, we compared the composition and seasonal succession of young‐of‐the‐year (YOY) fish assemblages in three similarly degraded river reaches differing in average vessel passages (2, 6 and 41 per day). Fish were caught by electrofishing biweekly between May and September. Multivariate tests were used to analyse differences between YOY‐fish assemblages and hurdle regression models applied to determine abiotic factors predicting fish occurrence and abundance. Roach (Rutilus rutilus) and perch (Perca fluviatilis) densities were compared. Roach larvae remain in the littoral zone while perch larvae shift to the pelagic zone immediately after hatch. YOY‐fish assemblage structure substantially changed along the traffic intensity gradient. In the high traffic intensity reach, species number and total fish density were markedly reduced compared to the other reaches. Roach densities were lowest in the high traffic intensity reach whereas perch densities did not decline along the gradient. Hurdle regressions confirmed a stronger effect of commercial navigation traffic intensity on roach than on perch. The total zooplankton biomass was highest in the high traffic intensity reach. Our results provide empirical evidence that intensive commercial navigation impoverishes fish assemblages in width‐restricted waterways. They underlined that in particular those species that have their first nursery habitats in shoreline areas were more affected by intensive commercial navigation than species whose larvae live predominantly pelagic. The results indicate that the negative effect of intensive navigation on riverine fish results primarily from the navigation‐induced hydraulic disturbances along the banks. Therefore, mitigation of navigation‐induced hydraulic forces is required to prevent degradation of fish communities in waterways. Copyright © 2010 John Wiley & Sons, Ltd.     

基于ZigBee无线通信的汽车倾斜度测量的应用

引言ZigBee是一种新的无线局域网传输标准,它是基于IEEE802.15.4协议基础的一个通信标准。IEEE802.15.4定义了协议的物理层和媒体介质访问控制层(MAC),而ZigBee定义了网络层、安全层和应用层,见图1。这样,     

Computer-aided generation of nonlinear reduced-order dynamicmacromodels. II. Stress-stiffened case

For pt. I see ibid., vol. 9, no. 2, p. 262-9 (2000). Reduced-order dynamic macromodels to describe the behavior of microelectromechanical system structures with stress stiffening are presented in this paper. The approach is based on potential and kinetic energy representations of selected fundamental modes of motion, modified to take account of stress stiffening. Energy data are calculated by several finite-element runs, fitted to polynomial functions, and used to develop the equations of motion according to Lagrangian mechanics. The accuracy and restrictions of these macromodels are shown     

Long time experience with the development of HTR fuel elements in Germany

The development of spherical fuel elements for HTR-designs in Germany is discussed. Special attention is given to the development, production and characterization (incl. kernel and coatings) as well as to the irradiation and post-irradiation examination of the different coated particle systems. It has been demonstrated in various irradiation tests which were supplemented by heating tests that for a modular HTR power plant (with a thermal output of 200 MJ s⁻¹) during the specified normal operation as well as in the case of incidents and even accidents, where the maximum fuel temperature will be below 1620 °C, the fission product release is very low. In this context, it must be mentioned that the present coated particle design has not yet been optimized for the combination of high burn-up and high temperature resistance under accident conditions. The TRISO fuel available is a result from fuel development for large HTR's with steam turbines in a time when the modular concept was not yet been invented although its capabilities inspired the design of modular reactors. Thus, there is still a huge potential for improvement of coated particles especially when plutonium or actinide burning is also taken into account.     

Silicon vibration sensor arrays with electrically tunable band selectivity

 Frequency selective vibration sensors for wear state recognition have been fabricated using surface near silicon bulk micromechaning (SCREAM). Capacitive detection combs convert the mechanical vibration into an electrical signal. Operating in a frequency selective resonant mode allows direct extraction of spectral information without Fourier transformation. To enlarge the measurement range they provide a frequency tuning capability by stress-stiffening which is achieved by electrostatic forces. Using force enhancing lever mechanism frequency variation of up to 100% of the base frequency has been measured with tuning voltages of 50 V. By arranging multiple cells with stepped base frequencies and overlapping tuning ranges the covered frequency range is widely extended. A fabricated array of ten cells is capable to continuously scan the range from 1 to 10 kHz. Received: 30 April 2001/Accepted: 11 June 2001