Oil Detection in a Coastal Marsh with Polarimetric Synthetic Aperture Radar (SAR)

The National Aeronautics and Space Administration’s airborne Uninhabited Aerial Vehicle Synthetic Aperture Radar (UAVSAR) was deployed in June 2010 in response to the Deepwater Horizon oil spill in the Gulf of Mexico. UAVSAR is a fully polarimetric L-band Synthetic Aperture Radar (SAR) sensor for obtaining data at high spatial resolutions. Starting a month prior to the UAVSAR collections, visual observations confirmed oil impacts along shorelines within northeastern Barataria Bay waters in eastern coastal Louisiana. UAVSAR data along several flight lines over Barataria Bay were collected on 23 June 2010, including the repeat flight line for which data were collected in June 2009. Our analysis of calibrated single-look complex data for these flight lines shows that structural damage of shoreline marsh accompanied by oil occurrence manifested as anomalous features not evident in pre-spill data. Freeman-Durden (FD) and Cloude-Pottier (CP) decompositions of the polarimetric data and Wishart classifications seeded with the FD and CP classes also highlighted these nearshore features as a change in dominant scattering mechanism. All decompositions and classifications also identify a class of interior marshes that reproduce the spatially extensive changes in backscatter indicated by the pre- and post-spill comparison of multi-polarization radar backscatter data. FD and CP decompositions reveal that those changes indicate a transform of dominant scatter from primarily surface or volumetric to double or even bounce. Given supportive evidence that oil-polluted waters penetrated into the interior marshes, it is reasonable that these backscatter changes correspond with oil exposure; however, multiple factors prevent unambiguous determination of whether UAVSAR detected oil in interior marshes

Charge distribution and electroluminescence in cross-linked polyethylene under dc field

The intent of this paper is to cross-correlate the information obtained by space charge distribution analysis and electroluminescence (EL) detection in cross-linked polyethylene samples submitted to dc fields, with the objective to make a link between space charge phenomena and energy release as revealed by the detection of visible photons. Space charge measurements carried out at different field levels by the pulsed electro-acoustic method show the presence of a low-field threshold, close to 15-20 kV mm-1, above which considerable space charge begins to accumulate in the insulation. Charges are seen to cross the insulation thickness through a packet-like behaviour at higher fields, starting at about 60-70 kV mm-1. EL measurements show the existence of two distinct thresholds, one related to the continuous excitation of EL under voltage, the other being transient EL detected upon specimen short circuit. The former occurs at values of field corresponding to charge packet formation and the latter to the onset of space charge accumulation. The correspondence between pertinent values of the electric field obtained through space charge and EL analyses provides support for the existence of degradation thresholds in insulating materials. Special emphasis is given to the relationship between charge packet formation and propagation, and EL. Although the two phenomena are observed in the same field range, it is found that the onset of continuous EL follows the formation at the electrodes of positive and negative space charge regions that extend into the bulk prior to the propagation of charge packets. Charge recombination appears to be the excitation process of EL since oppositely charged domains meet in the material bulk. To gain an insight into specific light-excitation processes associated with charge packet propagation, EL has been recorded for several hours under fields at which charge packet dynamics were evidenced. It is shown that current and luminescence oscillations are detected during charge packet propagation, and that they are in phase. The mechanisms underlying EL and charge packets are further considered on the basis of these results

Robustness Assessment of Life-Cycle-Management of CV Cables based on Degradation Diagnosis

Life-cycle management based on the degradation diagnosis is useful for preventing an unexpected failure and extending service life of electric power apparatuses, minimizing life-cycle cost. In our previous study, we formulated a numerical model of life-cycle management based on time-based maintenance and condition-based maintenance. Then, we applied the model for evaluating the economic effect of degradation diagnosis of power cables, assuming that the maximum length of water tree as a replacement criterion can be measured nondestructively. To carry out reliable life cycle management, however, accurate data on the relation between extent of degradation and failure probability or remaining life are necessary. In this study, we examine the influence of accuracy of the data used to determine the optimum diagnostic parameters and evaluate how the life-cycle cost is affected by the employment of inaccurate data. The results show that the condition-based maintenance with degradation diagnosis can be less subject to the accuracy of the back data and is possible to realize the reliable life-cycle management.journal articl

Eocene and Miocene extension, meteoric fluid infiltration, and core complex formation in the Great Basin (Raft River Mountains, Utah)

Metamorphic core complexes (MCCs) in the North American Cordillera reflect the effects of lithospheric extension and contribute to crustal adjustments both during and after a protracted subduction history along the Pacific plate margin. While the Miocene-to-recent history of most MCCs in the Great Basin, including the Raft River-Albion-Grouse Creek MCC, is well documented, early Cenozoic tectonic fabrics are commonly severely overprinted. We present stable isotope, geochronological (40Ar/39Ar), and microstructural data from the Raft River detachment shear zone. Hydrogen isotope ratios of syntectonic white mica (δ2Hms) from mylonitic quartzite within the shear zone are very low (-90‰ to -154‰, Vienna SMOW) and result from multiphase synkinematic interaction with surface-derived fluids. 40Ar/39Ar geochronology reveals Eocene (re)crystallization of white mica with δ2Hms ≥ -154‰ in quartzite mylonite of the western segment of the detachment system. These δ2Hms values are distinctively lower than in localities farther east (δ2Hms ≥ -125‰), where 40Ar/39Ar geochronological data indicate Miocene (18-15 Ma) extensional shearing and mylonitic fabric formation. These data indicate that very low δ2H surface-derived fluids penetrated the brittle-ductile transition as early as the mid-Eocene during a first phase of exhumation along a detachment rooted to the east. In the eastern part of the core complex, prominent top-to-the-east ductile shearing, mid-Miocene 40Ar/39Ar ages, and higher δ2H values of recrystallized white mica, indicate Miocene structural and isotopic overprinting of Eocene fabrics

Oligo-Miocene extensional tectonics and fluid flow across the Northern Snake Range detachment system, Nevada

The Northern Snake Range (Nevada) represents a spectacular example of a metamorphic core complex and exposes a complete section from the mylonitic footwall into the hanging wall of a fossil detachment system. Paired geochronological and stable isotopic data of mylonitic quartzite within the detachment footwall reveal that ductile deformation and infiltration of meteoric fluids occurred between 27 and 23 Ma. 40Ar/39Ar ages display complex recrystallization-cooling relationships but decrease systematically from 26.9 ± 0.2 Ma at the top to 21.3 ± 0.2 Ma at the bottom of footwall mylonite. Hydrogen isotope (δD) values in white mica are very low (-150 to-145 ‰) within the top 80-90 m of detachment footwall, in contrast to values obtained from the deeper part of the section where values range from-77 to-64 ‰, suggesting that time-integrated interaction between rock and meteoric fluid was restricted to the uppermost part of the mylonitic footwall. Pervasive mica-water hydrogen isotope exchange is difficult to reconcile with models of 40Ar loss during mylonitization solely by volume diffusion. Rather, we interpret the 40Ar/ 39Ar ages of white mica with low-δD values to date syn-mylonitic hydrogen and argon isotope exchange, and we conclude that the hydrothermal system of the Northern Snake Range was active during late Oligocene (27-23 Ma) and has been exhumed by the combined effects of ductile strain, extensional detachment faulting, and erosion. Copyright 2011 by the American Geophysical Union

Influence of Nanopore Diameter on Dielectric Permittivity of Epoxy/Open Nanoporous Silica Microcomposites

The purpose of this study was to obtain epoxy/open nanoporous silica (ONPS) microcomposites whose permittivity was lower than that of the unfilled epoxy resin. The ONPS filler comprised silica particles containing nanometric pores that were open at the particle surface. The particle size of the ONPS filler used in this study was on the order of micrometers. If air pores inside the ONPS filler remain unfilled with epoxy resin, the ONPS filler can be used as a low-permittivity filler for epoxy composites. In this study, we investigated the appropriate pore diameter of the ONPS filler for lowering the permittivity of epoxy/ONPS microcomposites. The permittivities of the epoxy/ONPS microcomposites were compared for ONPS fillers with the average pore diameters in the range from 0.6 nm to 15 nm. The permittivity of the epoxy/ONPS microcomposite whose average pore diameter was 3 nm was found to be lower than that of the unfilled epoxy resin. This low-permittivity characteristic can be explained quantitatively in terms of the pore volume. These results are expected to be useful for selecting ONPS fillers for epoxy/ONPS microcomposites that can be used as lowpermittivity insulating materials.journal articl

Filling ratio control of TiO2 and SiO2 in epoxy composites for permittivity-graded insulator with low coefficient of thermal expansion

The feasibility of a permittivity-graded epoxy insulator with a low coefficient of thermal expansion (CTE) was clarified by evaluating the dielectric and thermomechanical properties of TiO2/SiO2 epoxy composites, which were epoxy composites co-filled with TiO2 and SiO2 particles. Upon varying the filling ratio of TiO2 to SiO2 while keeping the total filler volume constant, the relative permittivity of the TiO2/SiO2 epoxy composites varied in the range of 3.5–7.5 in our experiment while the CTE remained similar to that of an aluminum conductor used in gas-insulated power apparatus. The range of the relative permittivity of the TiO2/SiO2 epoxy composites with a low CTE satisfied the condition for realizing a permittivity-graded epoxy insulator. The application of an appropriate gradient of the permittivity distribution to a permittivity-graded epoxy insulator with a low CTE resulted in the relaxation of the electric field on the surface of an insulator.journal articl

Dielectric properties and 3d printing of uv-cured acrylic composite with alumina microfiller

3D printing has potential to provide various solid insulating material such as a functionally graded material. It has not been clarified if the polymer-ceramic composite, the basic structure for the solid insulating material, can be 3D-printed even when the large amount of insulating ceramics fillers are introduced. This paper investigated the feasibility of the stereolithographic 3D printing of an insulating component using a UV-cured acrylic composite with a micorometric alumina fillers (alumina/UV-cured acrylic composite). Since scattering and absorption of UV light by alumina fillers were potential obstacle to UV curing, the UV light transmission characteristics of the alumina/UV-cured acrylic composite were obtained. The result provides the evidence that UV light reaches the back side of the layer of the composite and the resin is cured. As basic dielectric properties, permittivity and loss tangent of the alumina/UV-cured acrylic composites were obtained. It was confirmed that the permittivity of the composites was in accordance with the formulas for permittivity of two-component composite. By using the composite material, a 3D model of the conical insulating spacer was designed with physics simulation software and the data was printed out.journal articl

Hydrogen and strontium isotope ratios of deep-sea rocks from the western pacific

Water contents, and D/H and ^87Sr/^86Sr ratios were measured on the deep-sea rocks obtained from the western Pacific during the 17th cruise of R/V "Dmitry Mendeleev", the investigation by International Working Group of the IGCP "Ophiolites" in 1976. Values of D/H and water contents are fairly scattered, but ^87Sr/^86Sr ratios are distributed in a narrow range. No relationship among these values has been found.1976年IGCPオフィオライト・ワーキンググループが行った西太平洋の海底の調査（ドミトリー・メンデレフ号による）の際得られて岩石について、D/H・含水量・^87Sr/^86Srを測定した。試料採集地は第1図に示すとおりであり、結果は第1表に示してある。D/H・含水量はかなりの幅で変化を示すが、^87Sr/^86Srはほとんど変化しない。それらの間には相関関係がまったく見られない。成因論には何もふれられなかった。journal articl

Stable isotope geochemistry

This review is intended principally to be a reasonably comprehensive bibliography. It covers papers by workers in stable isotope geochemistry in the United States that have been published or presented at national meetings since the last quadrennial report. The titles of the papers in the bibliography are in most cases indicative of the general content, so only the highlights are described below