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Based on the Johnson's model of tiltrotor aircraft with nine degrees of freedom containing the assumptions of articulated rotor, rigid nacelle, elastic wing and clamped connections between the nacelle and wing, and considering the elastic connections between the nacelle and wing, the aeroelastic model of tiltrotor aircraft with eleven degrees of freedom for analysis of the whirl flutter of rotor/nacelle and instability of wing in forward flight has been established in this paper. The influences of the nacelle pitching and swing on the rotor inertial force and Coriolis force, the gyroscopic moment produced by the nacelle motion and rotor rotation, the supporting stiffness and damping of nacelle, the influence of nacelle motion on change in inflow of rotor and the influence of nacelle motion on wing motion have been considered in establishing the equations of motion of the rotor/nacelle/ wing coupled system. By using the system parameters of experimental model, the modal frequencies and damping ratios changing with the flight speed were calculated to determine the critical instability speed of the system. By influence of change in the supporting stiffness of nacelle on the critical instability speed, the dynamic instability form of tiltrotor aircraft in forward flight such as the vertical divergence motion of wing flutter or the whirl flutter of rotor/nacelle can be determined. According to the drawn motion trajectories of rotor hub center, the motion images of rotor hub center in the conditions of whirl flutter and wing instability of tiltrotor aircraft can be revealed, intuitively describing the motion patterns of rotor hub center in occurrence of the whirl flutter.

With the development of the technology for fabricating high-quality synthetic diamond and diamond waveguide structures, more and more researchers are being involved in exploring the particular optical properties of diamond for different applications. Because of its high refractive index and nontoxicity to biological species, diamond can be used to make micro-ring resonator to detect the concentration of liquid or gas. In this paper, a single micro-ring resonator model with diamond serving as the core layer is proposed. In the model, the vertical-section of the waveguide adopts a five-layer ridge-type waveguide structure based on As2S3, SiO2 and diamond, i.e. As2S3-SiO2-Diamond-SiO2-As2S3. To investigate the optical properties of the resonator, the vertical-section of the single straight waveguide, the coupling region of the direct waveguide, and the ring waveguide are simulated with the adopted operating wavelength =1550 nm based on the coupling mode theory and micro-ring resonance theory. In addition, the distribution of the field strength for the micro-ring is described at a resonant wavelength of 1543 nm. It is very important to explore the field intensity distribution of the micro-ring for understanding how the light transmits. The transmission characteristics of the micro-ring with the change of the distance between the straight waveguide and the ring waveguide in the coupling region are also simulated. The quality factor and the influence of the coupling coefficient change on the output spectrum are studied by the transfer matrix method and the micro-ring loss is discussed. It is shown that the micro-ring resonator designed with the diamond material has good transmission characteristics. When the resonant wavelength is 1543 nm, the resonant peak reaches more than -12 dB. The quality factor is about 1.54105. When the coupling coefficient k is 0.01, the free spectral range is about 40 nm. The coupling coefficient k is determined by the distance S of the coupling region. The results show that when S is equal to 50 nm, the output spectrum has a good extinction ratio and is better compared with the other values. The error of material processing is mainly affected by size, so the output spectrum near the distance S=50 nm is studied. The result shows that in the tiny change scope, the spectral output peak is linearly related to S. The structure we suggested in this paper expands the application scope of diamond in the field of optics, and provides some guiding significance for developing the optical integrated chips.

Graphene is a one-atom-thick planar sheet of sp2-bonded carbon atoms that are densely packed in a honeycomb crystal lattice. Graphene has been found to support plasmons in a wide range from infrared to terahertz. The confinement of plasmons in graphene is stronger than that on metallic surface. Moreover, the plasmon properties can be dynamically adjusted by doping or grating graphene. In this study, a composite structure comprised of graphene and subwavelength grating is proposed. Highly confined plasmons in graphene are excited by using a diffraction grating with guided mode resonance effect. The wave vector of plasmonic wave in graphene is far larger than that of light in vacuum. To excite plasmons in graphene with a freespace optical wave, their large difference in wave vector must be overcome. Optical gratings are widely used to compensate for wave vector mismatches. A diffraction wave generated by the grating structure can overcome the large wave vector difference and excite surface plasmons. The guided-mode resonance can greatly enhance the intensity of the diffraction field and the coupling efficiency between graphene and incident light. When the phase matching between illuminating wave and a guide mode supported by grating is achieved, guided-mode resonance effect occurs. A nearly 100% diffraction efficiency peak in the reflection or transmission spectrum occurs at a certain wavelength. In this study, the influences of graphene and grating structure on the local characteristics (the surface electric field Ex/Ein, quality factor Q, and effective mode area Seff) of surface plasmons are investigated. The effects of the structural parameters (the thickness of the buffer layer T2, the grating period p, the carrier mobility , and the Fermi level EF) on localization properties are analyzed by the finite element method (COMSOL). The results reveal that the localizations of the surface plasmons in the graphene surface is significantly improved at the certain parameters. 1) The increase of T2 will reduce the intensity of electric field on graphene (Ex/Ein), but the quality factor will obtain a certain increase. The excition of highly confined SPPs needs to improve Q and keep the intensity of Ex/Ein, so in this study T2 = 10 nm. 2) By adjusting the quality factor of SPPs can be improved significantly without changing the resonance frequency ( = 0.7 m2(Vs), Qmax = 1793). 3) Small changes in p and EF will make the resonance peak shift obviously, and the electric field on graphene is greatly enhanced (p = 235 nm, Ex/Ein = 3154; EF = 0.72 eV, and Ex/Ein = 3968). Strong localization leads to strong light-matter interaction, and thus the proposed structure has the potential to be used as sensors with high sensitivity and high-efficiency nonlinear optical devices, greatly expanding the application of graphene in nano optics.

Aiming at the lack of uniform mathematical model for multivariate graphs representation based on coordinate, a general model based on complex matrix is presented by analyzing and studying the traditional multivariate graphs such as radar chart, scatter plot, trigonometric polynomial graph, parallel coordinate, constellation graph. This model provides a general presentation frame for various multivariate graphs. It is useful for visualization data analyzing, data mining, and studying on a novel method of multivariate graphs.

In view of the complex wiring and poor reliability in traditional distributed temperature monitoring, microcontroller and wireless data transmission circuit were used to design a distributed temperature monitoring system. The method and principle of interfaces between microcontroller and peripheral circuits was analyzed. The interactive data comparison between master microcontroller and slave microcontroller was used to enhance the reliability of data transmission. The program language Visual Basic was used to develop the graphical interfaces to display the curve of temperature, to store the temperature data and to alert when temperature exceeds the limits. The experimental results show that the system works stably and it's temperature resolution can get to 0.0625 °C. Without wiring, the system is especially suitable for realizing distributed temperature on-line monitoring in large-scale industrial and agricultural production.

A wavelength scanning demodulation system based on continuous wave tunable frequency is given in this paper. Based on fiber Bragg grating's (FBG) axial strain character, the practical FBG strain sensor is designed. At the same time, tunable narrow-band light source, which is composed of wide-band light source and tunable optical filter, is adopted to demodulate multiplex signals. This method not only supply wider tunable range but also afford higher signal to noise ratio. A mixture multiplexing method that combines optical frequency domain reflectometry (OFDR) and wavelength division multiplexing (WDM) is proposed to address FBG sensing network. The proposed system scheme is testified to have faster demodulation and higher stability by analyzing theoretically and researching experimentally.

To satisfy bridge health monitoring and maintain, a novel low cost sensing system for simultaneous measurements of temperature, strain and pressure based on practical fiber Bragg grating (FBG) is reported in this paper. The main principles of multi-parameter are introduced. A wavelength scanning demodulation system based on continuous wave tunable frequency is designed. The practical FBG sensors have been successfully used in monitoring cable-stayed bridge during construction stage and service time. The experimental results indicate that practical FBG sensors can monitor the structure parameters for a long time, as well as have higher stability. The system can monitor the strain and vehicle flux of important position accurately. FBG sensors can not only supply precision data for bridgepsilas static and dynamic testing but also supply gist for bridgepsilas working state assessment and health diagnosis.