A new system has been developed and calibrated to measure the characteristics and distribution of skylight polarization. With a series of measurements obtained, we verified that the distribution of degree and angle of skylight polarization accords well with the predictions of Rayleigh scattering. The differences of the characteristics and distribution of skylight polarization across the principal plane owning to measurements’ errors have been analyzed and discussed.
Avian feather is the outstanding protein fiber structure that still lacks an interpretation generally acceptable in any detail. In this paper, asio otus feathers were morphological represented and their barbs were mechanical characterized by a developed micro-tensile tester with a load resolution of 0.25 mN and a displacement resolution of 10 nm. With a tensile loading speed at 0.02 μm/s, Young’s modulus of the flight feather barbs with length of 1450-1900 μm was calculated to be 3.13-3.66 GPa, higher than 1.47-2.04 GPa for the down feather barbs with length of 520-710 μm. It is concluded that the asio otus’s flight feathers on its wing and tail are more rigid than the down feathers on its body.
Measurements of seepage are fundamental for earth dam surveillance. However, it is difficult to establish an effective and practical dam seepage prediction model due to the nonlinearity between seepage and its influencing factors. Genetic Algorithm for Levenberg-Marquardt(GA-LM), a new neural network(NN) model has been developed for predicting the seepage of an earth dam in China using 381 databases of field data (of which 366 in 2008 were used for training and 15 in 2009 for testing). Genetic algorithm(GA) is an ecological system algorithm, which was adopted to optimize the NN structure. Levenberg-Marquardt (LM) algorithm was originally designed to serve as an intermediate optimization algorithm between the Gauss-Newton(GN) method and the gradient descent algorithm, which was used to train NN. The predicted seepage values using GA-LM model are in good agreement with the field data. It is demonstrated here that the model is capable of predicting the seepage of earth dams accurately. The performance of GA-LM has been compared with that of conventional Back-Propagation(BP) algorithm and LM algorithm with trial-and-error approach. The comparison indicates that the GA-LM model can offer stronger and better performance than conventional NNs when used as a quick interpolation and extrapolation tool.
The methods of on-chip integrated testing have a wide application with the development of the study for MEMS materials properties measurement in microscale. A novel on-chip integrated micro-tensile testing system is designed through system-level simulation based on macromodels to measure the fracture strength and fatigue mechanical properties of polysilicon thin films. The structure of testing instrument consists of V-beam electrothermal actuator, differential capacitance sensor, supporting spring and specimen. The capacitance signal is sensed and controlled by a second sigma-delta modulator circuit. The analytic macromodel of polysilicon thin film specimen considering geometric nonlinearity and the numerical reduced-order model of V-beam electrothermal actuator based on Krylov subspace projection are created separately and described in the MAST hardware language. The mechanical structure dimension size and circuit components parameters are determined and optimized according to system-level simulation. The computing result has shown that the self-build macromodels and the on-chip integrated test system are efficient and reliable.
Based on the OPAC (Optical Properties of Aerosols and Clouds) database, the impact of 8 typical aerosol types on the skylight polarization sensitive is researched. By combining the impact of cloud, the correction between aerosol and the polarization sensitive spectral of insects is analyzed. It can predict the polarization properties of different areas and provide the theoretical basis for the application of bionic micro-nanopolarization sensor.
This paper presents a precise angular algorithm for the imaging bionic polarization navigation sensor. The algorithm is targeted for a imaging sensor with bilayer nanowire polarizer which is multi-orientated of 0°, 60°, 120° and 90°, 150°, 210°. The algorithm is considered to extract intensity values of pixels in homogeneous regions, eliminate noise contained in image and compensate errors occured in the fabricaiton process of nanowire polarization filters. And the occlusion problem has to be compensated by neighboring pixels. The algorithm considered in this paper is able to solve overdetermined system of linear equations, and give a set of least square solutions of the Stokes parameters and the angle of polarization as output. The performance of the algorithm along with the experimental results of the angle measurement are also presented. Based on the comparison results, the algorithm achieves a best performance for the angle of polarization.
According to the requirement of the bionic navigation sensitive wave band of 380nm~520nm for sub-wavelength metallic gratings, in order to achieve performance indicators under the basic structural parameters. Analyzing TM transmittance and contrast ratio is carried out by employing finite-difference time-domain (FDTD) method. The result reveals that height, slit width and dielectric of grating impact TM transmittance and contrast ratio in various extents, and the greatest influence on the TM transmittance and contrast ratio is slit dielectric and slit width respectively.
Two kind of on-chip integrated fatigue bending test structures are designed through system-level simulation method based on macromodels to measure the fracture strength and fatigue mechanical properties of polysilicon thin films. The first on-chip fatigue test structure is actuated by V-beam thermal actuator, and the other test structure actuated by electrostatic comb. The static and dynamic analysis was performed by Coventorware Architect module using self-bulid reduced order model described with the MAST hardware language and some other commercial parts from Coventorware parts library. The structural dimension parameters are determined and optimized according to system-level simulation and the computing result has shown that the self-build macromodels and the on-chip integrated test system are efficient and reliable. Two kinds of polysilicon on-chip fatigue bending test structure were fabricated with two-layer polysilicon surface micromachining process in Institute of Microelectronics, Peking University.
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