Underwater Wireless Sensor Networks are significantly different from terrestrial sensor networks due to peculiar characteristics of low bandwidth, high latency, limited energy, node float mobility and high error probability. These features bring many challenges to the network protocol design of UWSNs. Several routing protocols have been developed in recent years for these networks. One of the m...

A methodology for design based research (DBR) into effective development and use of Multi-User Virtual Environments (MUVE) in vocational education is proposed. It blends software development with DBR with two theories selected to inform the methodology. Legitimate peripheral participation LPP (Lave & Wenger, 1991) provides a filter when thinking about vocational education because moving towards...

Nine quaternary (Al,Ga,In)–(P,As,Sb) semiconductor compounds lattice matched to InP are investigated theoretically. Direct bandgap, refractive index at 1.55 μm wavelength, and thermal conductivity are calculated as a function of the composition. These material properties are important, e.g. in distributed Bragg reflectors of vertical-cavity lasers. The alloy systems AlGaAsSb, AlGaPSb and GaInPS...

We demonstrate the mode locking of external-cavity semiconductor lasers by using a saturable Bragg reflector as an external reflector. Output pulses of 1.9 ps were generated from the semiconductor lasers without dispersion compensation. By coupling the output to a standard single-mode filter with a length of 35 m to compensate for the linear chirp, we have achieved mode-locked pulse durations a...

Boron and germanium doped highly photosensitive cladding is used in a novel design to achieve photosensitive Er/Yb doped fibres, enabling short strong gratings (length = 1 cm, reflectivity > 99%) to be written without hydrogenation. The high absorption at 980 nm in Er/Yb fibres allows efficient pump absorption over a short device length, ideal for achieving highly efficient single frequency fib...

Based on spectral beam combining we obtain 16 W of output power, combining two 1063 nm DBR-tapered diode lasers. The spectral separation within the combined beam can be used for subsequent sum-frequency generation. OCIS codes: (140.2020) Diode lasers; (140.3298) Laser beam combining; (190.2620) Harmonic generation and mixing

A commercial, conventional low‐energy electron diffraction apparatus is used to monitor Bragg intensity oscillations during the growth of Pt on Pd(100). The effect of substrate temperature between 80 and 400 K is investigated. Between 80 and 300 K, two to three Bragg oscillations are observed. The oscillation amplitude damps out quickly as film coverage increases at fixed temperature, but damp ...

A Mössbauer powder diffractometer was used to measure diffraction patterns from polycrystalline foils of Fe3Al. The intensities of Bragg diffractions were measured as a function of the energy of the incident photon. The bcc fundamental diffractions showed large changes in intensity as the incident energy was tuned through the nuclear resonances. These variations of diffraction intensity with in...

Optical filtering properties in a multichanneled transmission filter based on one-dimensional photonic crystal containing the coupled defects are theoretically investigated. The resonant transmission peaks are designed to be located within the photonic band gap of a defect-free photonic crystal. The number of peaks is directly equal to the number of the coupled defects. The positions of resonan...