Bed level changes in the surf zone during post-storm beach recovery

The study of post-storm beach recovery is important for economic development and the protection of life in coastal areas. In this study, field observations were conducted for 21 days in the surf zone of Dongdao Beach, Hailing Island, China, after tropical storm “Cempaka”. Data on depth, wave, Eulerian velocity, sediment, three-dimensional topography of the beach, and high-frequency variations in bed-level elevation were collected. The results showed that the beach experienced medium- to low- to medium-energy waves during field observations and covered two complete astronomical tide cycles. Contrary to the effect of wave energy conditions on beaches under normal wave conditions, a higher wave energy during beach recovery can promote silting and accelerate beach recovery. Tidal water level is an important factor affecting beach restoration, and a smaller tidal range is conducive to beach accretion. In a mixed semidiurnal tide, beach erosion and accretion occurred in the “highest tide” and “sub-highest tide” tidal cycles, respectively, and the combined effect of the two affected the change in the bed level in a mixed semidiurnal tide. After the storm, the hydrodynamic forcing mechanism and self-organization process of the sand bar jointly drove the formation of the topography of the bar channel in the surf zone. After the storm stopped, the spectral energy in free surface elevation was mainly distributed in the very low frequency and decayed rapidly at the infragravity band. The very low-frequency pulsation of the surf zone during recovery is a prominent feature of bed-level elevation, depth, and velocity. This study provides a good case for the study of hydrodynamic and bed level changes in the post-storm surf zone, as well as a reference for future studies of the intrinsic mechanisms post-storm beach recovery processes around the world

Laterally Driven Resonant Pressure Sensor with Etched Silicon Dual Diaphragms and Combined Beams

A novel structure of the resonant pressure sensor is presented in this paper, which tactfully employs intercoupling between dual pressure-sensing diaphragms and a laterally driven resonant strain gauge. After the resonant pressure sensor principle is introduced, the coupling mechanism of the diaphragms and resonator is analyzed and the frequency equation of the resonator based on the triangle geometry theory is developed for this new coupling structure. The finite element (FE) simulation results match the theoretical analysis over the full scale of the device. This pressure sensor was first fabricated by dry/wet etching and thermal silicon bonding, followed by vacuum-packaging using anodic bonding technology. The test maximum error of the fabricated sensor is 0.0310%F.S. (full scale) in the range of 30 to 190 kPa, its pressure sensitivity is negative and exceeding 8 Hz/kPa, and its Q-factor reaches 20,000 after wafer vacuum-packaging. A novel resonant pressure sensor with high accuracy is presented in this paper

Design and simulation of a differential and decoupled micromachined gyroscope

In this paper, a differential and decoupled micromachined gyroscope fabricated by through-etching the silicon substrate anodically bonded on the glass substrate was presented. The decoupled structure can make the sense mode frequency match with the drive mode frequency and reduce the quadrature error. The sensitivity is further improved by differential detection using antiphase oscillation of double masses along the drive axis. Finite-element simulation is performed with ANSYS software to analyze the vibration mode. The device employs silicon-on-glass gyroscope sensor chip processed with Deep Reactive Ion Etching (DRIE) and glass-silicon anodic bonding. Then it is tested at atmospheric pressure. Drive mode and sense mode are obtained as 2015 Hz and 1957 Hz which are closed to the simulated ones. Q factor of the drive and sense mode also can be gained as 56 and 3.4

Fabrication and morphological control of electrospun ethyl cellulose nanofibers

Conference Name:8th Annual IEEE International Conference on Nano/Micro Engineered and Molecular Systems, IEEE NEMS 2013. Conference Address: Suzhou, China. Time:April 7, 2013 - April 10, 2013.Institute of Electrical and Electronics Engineers (IEEE); IEEE Nanotechnology Council (NTC); Peking University; Soochow University; Chinese Academy of SciencesEthyl cellulous (EC) fibrous films were fabricated via electrospinning from solutions with various DMF/acetone volume ratios and the hydrophobic properties were investigated. The morphology of electrospun EC films reveals a conversion from beads to uniform nanofibers by decreasing the DMF/acetone ratio. Pure DMF solution leads to bead structures while uniform nanofibers can be obtained from DMF/acetone ratio of 2/3. The fibrous surfaces of electrospun EC films greatly improve their hydrophobicity with the average water contact angles range from 138° to 151°, exceeding that of spin-coating film (59°). The highest contact angle (151°) was found on the bead-on-string films prepared from the solution with DMF/acetone ratio of 4/1. For this hydrophobic capacity, the electrospun EC films would broaden their applications in the fields of coating and encapsulation. ? 2013 IEEE

Ni-electroplating of double-width micro-cantilever - art no 61090L

Conference Name:Conference on Micromachining and Microfabrication Process Technology XI. Conference Address: San Jose, CA.Micro-electroplating technology has an increasingly wider application in the fabrication of MEMS devices. In order to fabricate a double-width cantilever beam which has three different electroplated areas. The proper composition of the bath solution is obtained through experiments firstly in the paper. Then the effects of the peak of current density, duty cycle and pause time on the surface morphology of the electroplated nickel are studied experimentally to make sure the regulating range of pulsed parameters. And at last the double-width cantilever beam is fabricated using lithographic. micro-electroplating and sacrificial layer releasing processes. The results show that the surface of the beam is bright and smooth. and the nucleation rate increases steadily. But the thickness of the three parts with different width is different which can be modified by increasing the duty cycle and reducing the current density to some extent

Design and Experiment of a Jetting Dispenser Driven by Piezostack Actuator

To make up for the insufficiency and instability of contact dispensers that are used for fluid dispensing in microelectronic packaging, a noncontact jetting dispenser driven by a piezostack actuator is introduced in this paper. After describing the structural components and operating principle of the dispensing mechanism, a fluid model is presented to discuss the dynamic properties of the fluid and analyze the key parameters of the proposed dispenser. The ANSYS simulation software is used to design the displacement amplifier, which is an important component of the dispenser. The maximum displacement output of 323 mu m is obtained by optimizing. Subsequently, the dynamic behavior of the displacement amplifier is measured by an optical displacement sensor. The displacement change with the driving voltage amplitude and frequency is also investigated; the maximum displacement is 320 mu m, and the error between the simulation and the measurement result is just 0.75%. In order to verify the practicality of dispenser, experiments are conducted to examine the effects of the driving voltage, backpressure, working temperature, and distance between the nozzle and the collector on the jetting performance and droplet diameter. The dispenser can dispense droplets uniformly and steadily. Its maximum jetting frequency is 65 Hz, and droplets of 1.07-mm diameter are produced by a stainless steel nozzle of 0.25-mm diameter in the experimental study, with the variation of the droplet diameter being within +/- 2%

Emulated Analysis of the Preview-LQG Controller for Micromachined Tunneling Gyroscope

Conference Name:13th Annual Conference of Chinese-Society-of-Micro-Nano-Technology. Conference Address: Changchow, PEOPLES R CHINA. Time:SEP 28-30, 2011.Only when the tunneling gap is maintained near 10 angstrom can the micromachined tunneling gyroscope operate regularly to generate tunneling current which is so weak that it would be submerged by the thermal-mechanical noise, 1/f tunneling noise and so on. At the meantime, the dynamic range of the device will be reduced drastically by the nonlinearity of the tunneling effect. So a controller must be designed for the miniature tunneling gyroscope to realize a 10 angstrom tunneling gap to decrease the nonlinearity and so as to enlarge the band-width of the device. At the other hand, the signal-to-noise ratio can be raised by the controller. Because of the anti-interference and robusticity of the LQG control theory and the time-varying characteristic of Coriolis acceleration, the preview-LQG control strategy is selected to design the closed-loop system. The simulation results suggest that the tunneling gap can be controlled near its nominal value and the measured input angular rate can be estimated accurately by the preview-LQG controller even if the input angular rate is a slowly time-varying random signal

Electrohydrodynamic direct writing platform based on near-field electrospinning

Conference Name:14th Annual Conference and the 3rd International Conference of the Chinese Society of Micro-Nano Technology, CSMNT 2012. Conference Address: Hangzhou, China. Time:November 4, 2012 - November 7, 2012.Electrohydrodynamic Direct Writing (EDW) based on Near-Field Electrospinning (NFES) is a novel method to fabricate aligned micro/nano structure. In this article, linear motors and PIV&F servo control algorithm are introduced to set up an EDW experiment platform, by which patterned micro/nano structure can be direct-written. The motion track and position of collector is adjusted accurately by the platform, thus the deposition position and pattern of direct-written micro/nano structure can be controlled according to the pre-designed pattern. When motion velocity of collector higher than the ejection jet, micro/nano structure in straight line can be gained; but twisted structure can be direct-written under lower motion velocity of collector. The standstill of collector is introduced to overcome the pattern distortion that stems from the sharp change of collector motion track and the inertia of following jet. With the help of motion standstill, the patterned micro/nano structure without distortion can be direct-written, and more jet would be deposited at the corner of the pattern leaded to coiled structure. The EHD platform builds up the based for the industrial application of 1D micro/nano structure. ? 2013 Trans Tech Publications Ltd, Switzerland

Integrated Manufacturing of Suspended and Aligned Nanofibrous Scaffold for Structural Maturation and Synchronous Contraction of HiPSC-Derived Cardiomyocytes

Electrospun nanofiber constructs represent a promising alternative for mimicking the natural extracellular matrix in vitro and have significant potential for cardiac patch applications. While the effect of fiber orientation on the morphological structure of cardiomyocytes has been investigated, fibers only provide contact guidance without accounting for substrate stiffness due to their deposition on rigid substrates (e.g., glass or polystyrene). This paper introduces an in situ fabrication method for suspended and well aligned nanofibrous scaffolds via roller electrospinning, providing an anisotropic microenvironment with reduced stiffness for cardiac tissue engineering. A fiber surface modification strategy, utilizing oxygen plasma treatment combined with sodium dodecyl sulfate solution, was proposed to maintain the hydrophilicity of polycaprolactone (PCL) fibers, promoting cellular adhesion. Human-induced pluripotent stem cell (hiPSC)-derived cardiomyocytes (CMs), cultured on aligned fibers, exhibited an elongated morphology with extension along the fiber axis. In comparison to Petri dishes and suspended random fiber scaffolds, hiPSC-CMs on suspended aligned fiber scaffolds demonstrated enhanced sarcomere organization, spontaneous synchronous contraction, and gene expression indicative of maturation. This work demonstrates the suspended and aligned nano-fibrous scaffold provides a more realistic biomimetic environment for hiPSC-CMs, which promoted further research on the inducing effect of fiber scaffolds on hiPSC-CMs microstructure and gene-level expression