Fraunhofer UK Research

Abstract We present a method for modeling the reliability of wind turbine components during the early, intrinsic and deterioration failure stages of a turbine’s operational life. The method employs a Nelson-Aalen estimator to identify trends in failure behavior through time and a non-homogeneous Poisson process with a covariate selection procedure to identify key reliability drivers within partitions of the overall dataset. We demonstrate the utility of the methodology by using the converter system as a case study. All converter component categories except the converter cooling system show signs of prominent early failure behavior followed by a transition straight to deterioration failures. The effect of several design related factors are identified as significant drivers in both the early and deterioration stages.. We also investigate the environmental influences of mean absolute ambient humidity, mean ambient temperature, installation height and mean capacity factor, and find varying degrees of influence at different times throughout the operational life of the turbine.

An octave-spanning supercontinuum spectrum is generated in a photonic-crystal fiber using 1-GHz repetition rate, 30-fs diode-pumped Ti:sapphire laser. 390-mW of supercontinuum power is produced in about 550-1100 nm range from 850 mW of pump radiation.

The eye-safe range from 1.5-1.6μm has many applications such as in communications, sensing, and light detection and ranging (LIDAR) [1]. One particularly important application is wind surveying using Doppler LIDAR [2]. This requires high rep rate (>kHz) laser pulse that are narrow linewidth (MHz), short <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\sim 100\text{ns})$</tex> and high energy <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$(\mu \mathrm{J})$</tex> [3]. Currently this niche is filled by Er-doped fibre laser systems [4]. However, pulse energy scaling of these lasers is difficult [5]. To circumvent this, we propose a diamond master oscillator power amplifier (D-MOPA) as a final amplifier stage based on stimulated Raman scattering.

This article proposes a weighted histogram calibration method and an automatic calibration architecture to implement high-linearity time-to-digital converters (TDCs) in low-cost Advanced RSIC Machine (ARM)-based system-on-chips (SoCs). The proposed method significantly reduces the nonlinearity introduced by nonuniform bins. It offers automatic calibration without manual interventions using ARM processors. Besides, our design is cost-effective in hardware consumption. We implemented and evaluated a 16-channel TDC system in a low-cost Zynq-7000 ARM-based SoC, in which the programable logic is equivalent to a 28 nm Artix-7 FPGA. The proposed TDC offers a resolution of 9.83 ps with good uniformity, achieving an averaged <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{DN}}{{\rm{L}}_{{\rm{pk}} - {\rm{pk}}}}$</tex-math></inline-formula> of 0.38 LSB, and an averaged <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{IN}}{{\rm{L}}_{{\rm{pk}} - {\rm{pk}}}}$</tex-math></inline-formula> of 0.63 LSB.

In this Letter, we report on the development of an ultra-compact single-frequency Ti:sapphire laser under direct diode pumping. Single-longitudinal-mode operation is realized from a miniature plane-parallel resonator using a volume Bragg grating as an output coupler. InGaN laser diodes operating at around 470 nm and 490 nm with a combined power of 6.7 W are used as an optical pump. A maximum output power of 700 mW is generated during single-frequency operation at 813.4 nm. A laser linewidth of 2.4 MHz is measured during free-running operation, which is reduced to about 180 kHz when the laser is locked to an external reference cavity.

Optical Vortices In article number 2000087, Xiang Hao and co-workers show that by manipulating phase and amplitude at the back pupil of a high numerical-aperture (NA) objective, arbitrary longitudinal polarization vortices within the tightly focused light field are realized.

Abstract The first demonstration of laser action in ruby was made in 1960 by T. H. Maiman of Hughes Research Laboratories, USA. Many laboratories worldwide began the search for lasers using different materials, operating at different wavelengths. In the UK, academia, industry and the central laboratories took up the challenge from the earliest days to develop these systems for a broad range of applications. This historical review looks at the contribution the UK has made to the advancement of the technology, the development of systems and components and their exploitation over the last 60 years.

The identification of explosives residue and other harmful materials in field is a key problem to solve for world safety. Here we present a point-by-point imaging technique based on stand-off dual-comb spectroscopy carried out with QCL frequency combs using a fast scanning technique to provide hyperspectral images with species specific absorption spectra.