Search

We report an active–passive Q-switched laser based on graphene-covered microfiber modulator. The graphene-covered microfiber not only serves as a passive saturable absorber in a single laser cavity, but also can be used as an all-optical modulation device to synchronize two pulses generated from different wavelengths. The laser can not only actively change the output frequency of the Q-switched pulse to achieve the repetition frequency reduction, but also compress the pulse and increase the peak power of the output pulse. We successfully achieve the output of the active–passive Q-switched pulse using this fiber laser with a repetition rate from 41.1 kHz to 50.5 kHz. The fiber laser has potential applications in simultaneous output of multi-wavelength pulse.

Time synchronization in wireless sensor networks,aiming to provide a common sense of timing among distributed sensor nodes, is a key enabling technology for many applications, such as collaborative condition monitoring, time-of-flight localization and underwater navigation and tactical surveillance. In order to solve the challenges of the manufacturing tolerance and working condition variations in any real-world environments, a novel state-space model for pulse-coupled non-identical oscillators is proposed to model a realistic clock oscillator with nonidentical and time-varying frequency. A state feedback correction, referred to as hybrid coupling mechanism, is also proposed to ensure the system move into steady state, thus achieving time synchronization in wireless sensor networks. Furthermore, the intensive simulations of single-hop wireless sensor networks have been carried out to evaluate the performance of proposed pulsecoupled non-identical oscillators. It is shown that a partially connected wireless network consisting of 50 non-identical pulsecoupled oscillators can achieve the synchronization with the precision of $40us.$

We demonstrated an all fiber temperature sensor based on two pieces PDMS-graphene pliable composite film (PGF) covered microfiber ring resonator (MRR). This sandwich structure can significantly enhance the interaction between the transition light and the PGF through the evanescent wave of the MRR. The results show the light transmission changed exceed 16 dB. In the range of 30–60 °C, the proposed sensor demonstrated the temperature sensitivity of 0.544 dB °C−1 with R-square of 0.9982 during the heating process, and 0.536 dB °C−1 with R-square of 0.9976 during the cooling process. Our method introduces a novel temperature sensor with the advantages of high sensitivity, ultra compactness, corrosion resistance and robust, which we believe is greatly potential in applications such as data center temperature detection.

Digital elevation model (DEM), as an important product of digital photogrammetry and digital surveying and mapping, it plays an increasingly important role in the field of surveying and mapping and geographic information system. In this paper, it introduces the current generation methods of DEM by contour, and analyzes those interpolation methods that commonly are used to build DEM, and then describes the advantages and disadvantages of different building DEM methods systematically. Focusing on the DEM that represented by Grid and TIN, it compares the optimization methods of interpolation contour data systematically, and makes the contour interpolating DEM reflect the surface condition of the real nature more effectively.

In this letter, we report a novel microstrip interdigital hairpin resonator by having the parallel coupled lines in a conventional miniaturized hairpin resonator replaced by an interdigital capacitor. Equations are derived in order to design the resonator with an optimal physical length. It will be proved that the novel resonator can achieve even more size reduction than the conventional miniaturized hairpin resonator owing to the employment of the slow-wave structure. Finally, a four-pole cross-coupled bandpass filter using the optimal resonator is fabricated as verification

This paper investigates the optimal miniaturization of a helical resonator, which is in the form of a two turn helix. We theoretically demonstrate that its outmost dimension can be reduced to below 1% of the free space wavelength at resonance. Maximum miniaturization is achieved at an optimal metallic fill ratio of around 0.2 independent of diameter. Simulation and experimental results were used to validate the theoretical model and explore the miniaturization level achievable. The broadside coupled split ring resonators have the same optimal properties, but for identically sized resonator the helical design provides a factor of 2 greater miniaturization. © 2008 American Institute of Physics.

The use of radial stubs in microstrip stepped-impedance resonator bandpass filters is investigated. It is noticed that the stopband rejection level can be enhanced with minor deterioration in the filter's passband characteristics. Demonstration filters were fabricated with the measured and simulated results presented.

A novel compact microstrip resonator is proposed with its equivalent circuit. Its resonant properties can then be analytically predicted. Finally, a bandpass filter using this resonator is designed, fabricated and measured, providing an excellent verification on its attractive features such as outstanding spurious response and compactness

Network coordinates (NC) system is an efficient mechanism for Internet distance prediction with scalable measurements. The intrinsical cause for the unsatisfactory accuracy of the simulation-based NC algorithms has been identified. Then Pharos, a fully decentralised and hierarchical scheme, is proposed to solve this problem. Pharos leverages multiple coordinate sets at different distance scales, with the right scale being chosen for prediction each time. We evaluate the performance of Pharos system with the King data set and latency data from PlanetLab, and compare it with the representative NC system, Vivaldi. The experimental results show that Pharos greatly outperforms Vivaldi in Internet distance prediction without adding any significant overhead. Our extensive evaluation results also demonstrate that Pharos can significantly improve the performance in distributed Internet applications, such as overlay multicast and server selection.