Performance analysis and testing of a 250 kW medium-speed brushless doubly-fed induction generator

This study presents the performance analysis and testing of a 250 kW medium-speed brushless doubly-fed induction generator (DFIG), and its associated power electronics and control systems. The experimental tests confirm the design, and showthe system's steady-state and dynamic performance and grid low-voltage ride- through capability. The medium-speed brushless DFIG in combination with a simplified two-stage gearbox promises a low-cost low-maintenance and reliable drivetrain for wind turbine applications. © The Institution of Engineering and Technology 2013.

Lateral response of monopiles using centrifuge testing and finite element analysis

Offshore wind capacity is expected to grow exponentially over the next decade resulting in the production of a considerable amount of renewable energy. Monopiles are currently the most popular type of foundation for supporting offshore wind turbines in shallow to medium depth waters. In this paper, the load-deformation response of a 3.8 m diameter monopile installed in soft clays when subjected to axial and lateral loading is investigated using centrifuge testing and soil pore-fluid coupled three-dimensional finite element analysis. Monopile deformation is principally assessed in terms of its lateral displacements and bending moments. Its behaviour as a short rigid pile is discussed using concepts such as its rotation at mudline and the pile depth at which pivoting occurs. © 2014 Taylor & Francis Group.

Centrifuge testing of monopile in clay under monotonic loads

The monopile is at present the most widely applied foundation concept for offshore wind turbines. Monopiles are designed utilising the well-established p-y method. Despite being well-established, there are multiple issues and limitations regarding its use. Investigation into the lateral behaviour of monopiles was carried out by performing monotonic and cyclic lateral load tests on an aluminium model monopile in the centrifuge. The monotonic responses and the behaviour of the monopile are described. Differences between the experimental and DNV design p-y curves and their implications are discussed. Efforts to characterise the shear force acting at the pile toe are also discussed. The results highlight the possible deficiencies of utilising the conventional DNV design p-y curves to design monopiles to resist cyclic lateral loads and the importance of research into the cyclic loading behaviour of monopiles to better improve their design to resist long-term cyclic loads. © 2014 Taylor & Francis Group.

Centrifuge testing of monopiles subject to cyclic lateral loading

Monopiles supporting offshore wind turbines are subjected to cyclic lateral loading. The properties of the applied cyclic lateral load are known to have an effect on the accumulation of permanent displacement and rotation at the pile head. The results of centrifuge testing on model piles show that certain loading regimes lead to the development of locked in soil stresses around the pile. These locked in soil stresses change the stiffness of the monopile response to cyclic lateral loading and the natural frequency of the pile-soil system. © 2014 Taylor & Francis Group.

Development of a multidirectional simple shear testing device

A new simple shear testing device capable of applying multidirectional loading to soil specimens has been developed. The Texas A&M University multidirectional simple shear (TAMU-MDSS) device provides the ability to apply a large range of shear stresses and complex loading paths, such as figure-eight and circular patterns, to a cylindrical soil specimen confined by a wire-reinforced membrane. The load and torque experienced by the sample are directly measured by a multi-axis load cell installed above the specimen. Backpressure saturation of the specimen is made possible by the devicés ability to apply pressure in the chamber and backpressure to the water lines. Excess pore pressure is measured by a pressure transducer during the shearing phase of the testing. This paper describes the development of the TAMU-MDSS system and the capabilities of the device and presents test results on saturated clay soil specimens subjected to monotonic, unidirectional cyclic, and multidirectional loading. Copyright © 2013 by ASTM International.

SLP: A zero-contact non-invasive method for pulmonary function testing

Structured Light Plethysmography (SLP) is a novel non-invasive method that uses structured light to perform pulmonary function testing that does not require physical contact with a patient. The technique produces an estimate of chest wall volume changes over time. A patient is observed continuously by two cameras and a known pattern of light (i.e. structured light) is projected onto the chest using an off-the-shelf projector. Corner features from the projected light pattern are extracted, tracked and brought into correspondence for both camera views over successive frames. A novel self calibration algorithm recovers the intrinsic and extrinsic camera parameters from these point correspondences. This information is used to reconstruct a surface approximation of the chest wall and several novel ideas for 'cleaning up' the reconstruction are used. The resulting volume and derived statistics (e.g. FVC, FEV) agree very well with data taken with a spirometer. © 2010. The copyright of this document resides with its authors.

Testing the relationships of Chinese freshwater Unionidae (bivalvia) based on analysis of partial mitochondrial 16s rRNA sequences

This study presents partial mitochondrial 16S rRNA sequences of 13 unionid bivalve species from China and analyses their relationships in combination with known data of 21 American mussels. According to our results, Chinese unionids, formerly regarded as two subfamilies, should be divided into three subfamilies: Ambleminae, Anodontinae and Unioninae. The genera Hyriopsis, Solenaia, Lamprotula and Ptychorhynchus, hitherto placed in Unioninae or Anodontinae, should be moved to the subfamily Ambleminae, demonstrated for the first time from China. The other genera recorded from China are suggested to belong to Anodontinae and Unioninae, which is in agreement with traditional classifications, except for the genus Lepidodesma.

Effects of indium ion implantation on the total dose hardness of fully depleted SOI NMOSFET

In this work, we investigate the effects of the indium ion implantation towards the back-channel interface on the total dose hardness of the n-channel SOI MOSFET. The results show that the indium implant has slight impact on the normal threshold voltage while preserving low leakage current after irradiation. The advantage is attributed to the narrow as-implanted and postanneal profile of the indium implantation. Two-dimensional simulations have been used to understand the physical mechanisms of the effects.

Effect of counterpart on the tribological behavior and tribo-induced phase transformation of Si

The tribological behaviors and phase transformation of single crystal silicon against Si3N4, Ruby and steel were investigated in this study. It was found that the strong chemical action between silicon and Fe was the key factor to the tribological behavior of silicon as slid against steel. SEM and Raman spectroscopy indicated that phase transformation of single crystal silicon occurred during the running-in period at low sliding velocity as slid against Si3N4 and Ruby. and gave birth to single or a mixture phase of Si-III, Si-XII and amorphous silicon. The high hardness of counterpart and the absence of chemical action between silicon and counterpart facilitated the phase transformation of single crystal silicon. (C) 2008 Elsevier Ltd. All rights reserved.

Bulge testing and fracture properties of plasma-enhanced chemical vapor deposited silicon nitride thin films

The mechanical properties and fracture behavior of silicon nitride (SiNx) thin film fabricated by plasma-enhanced chemical vapor deposition is reported. Plane-strain moduli, prestresses, and fracture strengths of silicon nitride thin film; deposited both oil a bare Si substrate and oil a thermally oxidized Si substrate were extracted using bulge testing combined with a refined load-deflection model of long rectangular membranes. The plane-strain modu i and prestresses of SiNx thin films have little dependence on the substrates, that is, for the bare Si substrate, they are 133 +/- 19 GPa and 178 +/- 22 MPa, respectively, while for the thermally oxidized substrate, they are 140 +/- 26 Gila and 194 +/- 34 MPa, respectively. However, the fracture strength values of SiNx films grown on the two substrates are quite different, i.e., 1.53 +/- 0.33 Gila and 3.08 +/- 0.79 GPa for the bare Si substrate a A the oxidized Si substrate, respectively. The reference stresses were computed by integrating the local stress of the membrane at the fracture over the edge, Surface, and volume of the specimens and fitted with the Weibull distribution function. For SiNx thin film produced oil the bare Si Substrate, the Volume integration gave a significantly better agreement between data and model, implying that the volume flaws re the dominant fracture origin. For SiNx thin film grown on the oxidized Si substrate, the fit quality of surface and edge integration was significantly better than the Volume integration, and the dominant surface and edge flaws could be caused by buffered HF attacking the SiNx layer during SiO2 removal. Crown Copyright (C) 2008 Published by Elsevier B.V. All rights reserved.

Silicon-on-insulating multi-layers for total-dose irradiation hardness

Silicon-on-insulating multi-layer (SOIM) materials were fabricated by co-implantation of oxygen and nitrogen ions with different energies and doses. The multilayer microstructure was investigated by cross-sectional transmission electron microscopy. P-channel metal-oxide-semiconductor (PMOS) transistors and metal-semiconductor-insulator-semiconductor (MSIS) capacitors were produced by these materials. After the irradiated total dose reaches 3 x 10(5) rad (Si), the threshold voltage of the SOIM-based PMOS transistor only shifts 0.07 V, while thin silicon-on-insulating buried-oxide SIMOX-based PMOS transistors have a shift of 1.2V, where SIMOX represents the separated by implanted oxygen. The difference of capacitance of the SOIM-based MSIS capacitors before and after irradiation is less than that of the thin-box SIMOX-based MSIS capacitor. The results suggest that the SOIM materials have a more remarkable irradiation tolerance of total dose effect, compared to the thin-buried-oxide SIMOX materials.

Radiation hardness improvement of separation-by-implantation-of-oxygen/silicon-on-insulator material by nitrogen ion implantation

In our work, nitrogen ions were implanted into separation-by-implantation-of-oxygen (SIMOX) wafers to improve the radiation hardness of the SIMOX material. The experiments of secondary ion mass spectroscopy (SIMS) analysis showed that some nitrogen ions were distributed in the buried oxide layers and some others were collected at the Si/SiO2 interface after annealing. The results of electron paramagnetic resonance (EPR) suggested the density of the defects in the nitrided samples changed with different nitrogen ion implantation energies. Semiconductor-insulator-semiconductor (SIS) capacitors were made on the materials, and capacitance-voltage (C-V) measurements were carried out to confirm the results. The super total dose radiation tolerance of the materials was verified by the small increase of the drain leakage current of the metal-oxide-semiconductor field effect transistor with n-channel (NMOSFETs) fabricated on the materials before and after total dose irradiation. The optimum implantation energy was also determined.

Improvement of the radiation hardness of SIMOX buried layers using nitrogen implantation

An investigation of hardening the buried oxides (BOX) in separation by implanted oxygen (SIMOX) silicon-on-insulator (SOI) wafers to total-dose irradiation has been made by implanting nitrogen into the BOX layers with a constant dose at different implantation energies. The total-dose radiation hardness of the BOX layers is characterized by the high frequency capacitance-voltage (C-V) technique. The experimental results show that the implantation of nitrogen into the BOX layers can increase the BOX hardness to total-dose irradiation. Particularly, the implantation energy of nitrogen ions plays an important role in improving the radiation hardness of the BOX layers. The optimized implantation energy being used for a nitrogen dose, the hardness of BOX can be considerably improved. In addition, the C-V results show that there are differences between the BOX capacitances due to the different nitrogen implantation energies.

Electron beam and laser testing on the novel stripixel detectors

The novel Si stripixel detector, developed at BNL (Brookhaven National Laboratory), has been applied in the development of a prototype Si strip detector system for the PHENIX Upgrade at RHIC. The Si stripixel detector can generate X-Y two-dimensional (2D) position sensitivity with single-sided processing and readout. Test stripixel detectors with pitches of 85 and 560 mu m have been subjected to the electron beam test in a SEM set-up, and to the laser beam test in a lab test fixture with an X-Y-Z table for laser scanning. Test results have shown that the X and Y strips are well isolated from each other, and 2D position sensitivity has been well demonstrated in the novel stripixel detectors. (c) 2005 Elsevier B.V. All rights reserved.