Learning models of plant behavior for anomaly detection and condition monitoring

Providing engineers and asset managers with a too] which can diagnose faults within transformers can greatly assist decision making on such issues as maintenance, performance and safety. However, the onus has always been on personnel to accurately decide how serious a problem is and how urgently maintenance is required. In dealing with the large volumes of data involved, it is possible that faults may not be noticed until serious damage has occurred. This paper proposes the integration of a newly developed anomaly detection technique with an existing diagnosis system. By learning a Hidden Markov Model of healthy transformer behavior, unexpected operation, such as when a fault develops, can be flagged for attention. Faults can then be diagnosed using the existing system and maintenance scheduled as required, all at a much earlier stage than would previously have been possible

Gallium oxide and gadolinium gallium oxide insulators on Si δ-doped GaAs/AlGaAs heterostructures

Test devices have been fabricated on two specially grown GaAs/AlGaAs wafers with 10 nm thick gate dielectrics composed of either Ga<sub>2</sub>O<sub>3</sub> or a stack of Ga<sub>2</sub>O<sub>3</sub> and Gd<sub>0.25</sub>Ga<sub>0.15</sub>O<sub>0.6</sub>. The wafers have two GaAs transport channels either side of an AlGaAs barrier containing a Si delta-doping layer. Temperature dependent capacitance-voltage (C-V) and current-voltage (I-V) studies have been performed at temperatures between 10 and 300 K. Bias cooling experiments reveal the presence of DX centers in both wafers. Both wafers show a forward bias gate leakage that is by a single activated channel at higher temperatures and by tunneling at lower temperatures. When Gd<sub>0.25</sub>Ga<sub>0.15</sub>O<sub>0.6</sub> is included in a stack with 1 nm of Ga<sub>2</sub>O<sub>3</sub> at the interface, the gate leakage is greatly reduced due to the larger band gap of the Gd<sub>0.25</sub>Ga<sub>0.15</sub>O<sub>0.6</sub> layer. The different band gaps of the two oxides result in a difference in the gate voltage at the onset of leakage of ~3 V. However, the inclusion of Gd<sub>0.25</sub>Ga<sub>0.15</sub>O<sub>0.6</sub> in the gate insulator introduces many oxide states (≤4.70Ã�Â�10<sup>12</sup> cm<sup>âÂ�Â�2</sup>). Transmission electron microscope images of the interface region show that the growth of a Gd<sub>0.25</sub>Ga<sub>0.15</sub>O<sub>0.6</sub> layer on Ga<sub>2</sub>O<sub>3</sub> disturbs the well ordered Ga<sub>2</sub>O<sub>3</sub>/GaAs interface. We therefore conclude that while including Gd<sub>0.25</sub>Ga<sub>0.15</sub>O<sub>0.6</sub> in a dielectric stack with Ga<sub>2</sub>O<sub>3</sub> is necessary for use in device applications, the inclusion of Gd decreases the quality of the Ga<sub>2</sub>O<sub>3</sub>/GaAs interface and near interface region by introducing roughness and a large number of defect states

Monitoring Oyster Point seagrasses : 1995 to 1999

In the present report, an assessment of changes in seagrass distribution and abundance since the baseline (November 1995) and previous monitoring surveys of December 1997 and November 1998 is included. We provide a quantification of changes between years and comment on the possible impacts of the dredging program

Preliminary evaluation of an acoustic technique for mapping tropical seagrass habitats

Seagrass meadows in Queensland are important nursery habitat for commercial species of penaeid prawns and fish. Seagrasses are essential food for dugong, Dugong dugon, and green sea turtles, Chelonia mydas (Linnaeus) and act as nutrient and sediment sinks. Seagrasses in coastal regions play important roles in maintaining sediment stability and water clarity. Coastal seagrass meadows are therefore an important resource economically and ecologically. Information on the species composition, abundance and distribution of seagrasses is used by management to zone for protection of seagrass habitats

Using relative sea-level data to constrain the deglacial and Holocene history of southern Greenland

This paper presents new Holocene relative sea-level (RSL) data collected from isolation basins close to the town of Paamiut in south west Greenland. The data shows a rapid fall from a marine limit of c. 52 m asl at c. 10.9 cal. ka BP to close to present by c. 9.5 cal. ka BP, at rates of up to c. 32 mm/yr, falling below present for the majority of the Holocene before rising to present in the last 2000 years. The elevation of the RSL lowstand is not well constrained, but was at least below −3 m. This pattern of rapid RSL fall during the early Holocene matches the pattern seen at other southern Greenland locations suggesting rapid, largely simultaneous ice retreat from the area surrounding the Qassimiut Lobe at the start of the Holocene, occurring c. 2000 years after the initial deglaciation of the extreme southern tip of Greenland. The RSL histories from this and other southern Greenland locations are distinct to those recorded further north along the west coast, and are in broad agreement with a pattern of vertical land motion and RSL predicted by the Huy2 model (Simpson et al., 2009), which predicts an 80 m drop in the contribution of vertical land motion to RSL at 10 cal. ka BP between Sisimiut and Paamiut on the west coast. Despite this broad-scale spatial agreement between the RSL data and the Huy2 model, it fails to satisfactorily predict the Holocene RSL histories at Paamiut and other southern Greenland locations. Sensitivity tests indicate that the data-model misfits are most likely due to an over-estimate of the forcing during the Holocene Thermal Maximum (or the response to this forcing) in southern Greenland and error in the North American ice sheets component of the background deglaciation model. Our new data suggests that much of the southern part of the ice sheet acted differently to the area further north. However RSL changes at Paamiut are also largely impacted by regional and larger-scale processes including a bulls-eye of uplift centred on the west, the impact of the Holocene Thermal Maximum and the influence of the collapse of the North American ice sheets

Modelling the effects of sediment compaction on salt marsh reconstructions of recent sea-level rise

This paper quantifies the potential influence of sediment compaction on the magnitude of nineteenth and twentieth century sea-level rise, as reconstructed from salt marsh sediments. We firstly develop a database of the physical and compression properties of low energy intertidal and salt marsh sediments. Key compression parameters are controlled by organic content (loss on ignition), though compressibility is modulated by local-scale processes, notably the potential for desiccation of sediments. Using this database and standard geotechnical theory, we use a numerical modelling approach to generate and subsequently ‘decompact’ a range of idealised intertidal stratigraphies. We find that compression can significantly contribute to reconstructed accelerations in recent sea level, notably in transgressive stratigraphies. The magnitude of this effect can be sufficient to add between 0.1 and 0.4 mm yr−1 of local sea-level rise, depending on the thickness of the stratigraphic column. In contrast, records from shallow (<0.5 m) uniform-lithology stratigraphies, or shallow near-surface salt marsh deposits in regressive successions, experience negligible compaction. Spatial variations in compression could be interpreted as ‘sea-level fingerprints’ that might, in turn, be wrongly attributed to oceanic or cryospheric processes. However, consideration of existing sea-level records suggests that this is not the case and that compaction cannot be invoked as the sole cause of recent accelerations in sea level inferred from salt marsh sediments

Baseline survey of Hinchinbrook region seagrasses - October (spring) 1996

Current coastal zone management issues in the Hinchinbrook region include protection of fisheries habitats, dugong habitat areas and increases in aquaculture, agriculture and tourist operations. A regional coastal management plan which is being developed, also requires detailed information on seagrass resources for the coastal zone from Dunk Island in the north, to Cleveland Bay in the south. Decreases in estimates of dugong abundance in the southern half of the Great Barrier Reef region since the 1980's have also prompted the need for detailed baseline and monitoring surveys of seagrasses in this and other regions

Sea-level rise due to polar ice-sheet mass loss during past warm periods

Interdisciplinary studies of geologic archives have ushered in a new era of deciphering magnitudes, rates, and sources of sea-level rise from polar ice-sheet loss during past warm periods. Accounting for glacial isostatic processes helps to reconcile spatial variability in peak sea level during marine isotope stages 5e and 11, when the global mean reached 6 to 9 meters and 6 to 13 meters higher than present, respectively. Dynamic topography introduces large uncertainties on longer time scales, precluding robust sea-level estimates for intervals such as the Pliocene. Present climate is warming to a level associated with significant polar ice-sheet loss in the past. Here, we outline advances and challenges involved in constraining ice-sheet sensitivity to climate change with use of paleo–sea level records

Static quantities of the W boson in the SU_L(3) X U_X(1) model with right-handed neutrinos

The static electromagnetic properties of the $W$ boson, $\Delta \kappa$ and $\Delta Q$, are calculated in the SU_L(3)} \times U_X(1) model with right-handed neutrinos. The new contributions from this model arise from the gauge and scalar sectors. In the gauge sector there is a new contribution from a complex neutral gauge boson $Y^0$ and a singly-charged gauge boson $Y^\pm$. The mass of these gauge bosons, called bileptons, is expected to be in the range of a few hundreds of GeV according to the current bounds from experimental data. If the bilepton masses are of the order of 200 GeV, the size of their contribution is similar to that obtained in other weakly coupled theories. However the contributions to both $\Delta Q$ and $\Delta \kappa$ are negligible for very heavy or degenerate bileptons. As for the scalar sector, an scenario is examined in which the contribution to the $W$ form factors is identical to that of a two-Higgs-doublet model. It is found that this sector would not give large corrections to $\Delta \kappa$ and $\Delta Q$.Comment: New material included. Final version to apppear in Physical Review