東澳大利亞悉尼盆地南部二疊紀的地層、沈積環境與盆地演化

The latest Carboniferous to Triassic Sydney-Gunnedah-Bowen Basin System in the eastern Australia is an elongate structural basin that locates between the Lachlan Caledonian Fold Belt in the west and the New England Fold Belt in the east. Extending from the Gunnedah district in the north to the Batemans Bay in the south, the Sydney Basin is a subbasin located in the southern part of the Sydney-Gunnedah-Bowen Basin System. The Permian in Sydney Basin consists of sedimentary sequences of fluvial, delta, littoral and shallow marine environments, as well as volcanic rocks. In the southwest of southern Sydney Basin, the Permian unconformably onlaps the highly deformed and metamorphosed Lachlan Fold Belts. The Permian System from the southern Sydney Basin comprises the Lower Permian Tallaterang Group (consisting of Clyde Coal Measures and Wasp Head Formation), Shoalhaven Group ( consisting of the Lower Permian Yadboro & Tallong Conglomerate, Yarrunga Coal Measures, Pebbly Beach Formation, Snapper Point Formation and the Middle Permian Wandrawandian Siltstone, Nowra Sandstone, Berry Siltstone and Broughton Formation) and the Upper Permian Illwarra Coal Measures. From the latest Carboniferous to the Middle Triassic, the SydneyBowen Basin had experienced different tectonic phases from a back-arc extensional regime to a typical foreland basin: a back-arc extensional phase, a passive thermal sag phase and a flexural loading and increased compressional phase.

Metrics of the normal cornea : anterior segment imaging with the Visante OCT

Purpose:  The purpose of the study was to obtain anterior segment biometry for 40 normal eyes and to measure variables that may be useful to design large diameter gas permeable contact lenses that sit outside the region normally viewed by corneal topographers. Also, the distribution of these variables in the normal eye and how well they correlated to each other were determined.

Methods:  This is a cross-sectional study, in which data were collected at a single study visit. Corneal topography and imaging of the anterior segment of the eye were performed using the Orbscan II and Visante OCT. The variables that were collected were horizontal K reading, central corneal/scleral sagittal depth at 15 mm chord, and nasal and temporal angles at the 15 mm chord using the built-in software measurement tools.

Results:  The central horizontal K readings for the 40 eyes were 43 ± 1.73 D (7.85 ± 0.31 mm), with ± 95% confidence interval (CI) of 38.7 (8.7 mm) and 46.6 D (7.24 mm). The mean corneal/scleral sagittal depth at the 15 mm chord was 3.74 ± 0.19 mm and the range was 3.14 to 4.04 mm. The average nasal angle (which was not different from the temporal angle) at the 15 mm chord was 39.32 ± 3.07 degrees and the ± 95%CI was 33.7 and 45.5 degrees. The correlation coefficient comparing the K reading and the corneal/scleral sagittal depth showed the best correlation (0.58, p < 0.001). The corneal/scleral sagittal depth at 15 mm correlated less with the nasal angle (0.44, p = 0.004) and the weakest correlation was for the nasal angle at 15 mm with the horizontal readings (0.32, p = 0.046).

Conclusion:  The Visante OCT is a valuable tool for imaging the anterior segment of the eye. The Visante OCT is especially effective in providing the biometry of the peripheral cornea and sclera and may help in fitting GP lenses with a higher percentage of initial lens success, when the corneal sag and lens sag are better matched.

Improving fault ride through capability of DFIG during RSC flashover fault

Wind power generation is growing rapidly. However, maintaining the wind turbine connection to grid is a real challenge. Recent grid codes require wind turbines to maintain connected to the grid even during fault conditions which increases concerns about its sensitivity to external faults. So, researchers have given attention to investigating the impact of various external faults, and grid disturbances such as voltage sag and short circuit faults, on the fault ride through (FRT) capability of the doubly fed induction generator (DFIG). However, no attention has been given to the impact of internal faults on the dynamic performance of the machine when the fault occurs within the voltage source converters (VSCs) that interface the DFIG with the grid. This paper investigates the impact of the rotor side converter (RSC) IGBT flashover fault on the common coupling (PCC) reactive power and the FRT is proposed. The DFIG compliance with numerous and recently released FRT grid codes under the studied fault, with and without the STATCOM are examined and compared. Furthermore, the capability of a proposed controller to bring the voltage profile at the point of PCC to the nominal steady-state level; maintain the unity power factor operation; and, maintain the connection of the wind turbine to the grid are examined

Early Triassic (early Olenekian) life in the interior of East Gondwana: Mixed marine-terrestrial biota from the Kockatea Shale, Western Australia

A new terrestrial-marine assemblage from the lower beds of a thin outcrop section of the Kockatea Shale in the northern Perth Basin, Western Australia, contains a range of fossil groups, most of which are rare or poorly known from the Lower Triassic of the region. To date, the collection includes spinose acritarchs, organic-cemented agglutinated foraminifera, lingulids, minute bivalves and gastropods, ammonoids, spinicaudatans, insects, austriocaridid crustaceans, actinopterygians, a temnospondyl-like mandible, plant remains, and spores and pollen. Of these groups, the insects, crustaceans and macroplant remains are recorded for the first time from this unit. Palynomorphs permit correlation to nearby sections where conodonts indicate an early Olenekian (Smithian) age. The locality likely represents the margin of an Early Triassic shallow interior sea with variable estuarine-like water conditions, at the southwestern end of an elongate embayment within the East Gondwana interior rift-sag system preserved along the Western Australian margin. Monospecific spinose acritarch assemblages intertwined with amorphous organic matter may represent phytoplankton blooms that accumulated as mats, and suggest potentially eutrophic surface waters. The assemblage represents a mixure of marine and terrestrial taxa, suggesting variations in water conditions or that fresh/brackish-water and terrestrial organisms were transported from adjacent biotopes. Some of the lower dark shaly beds are dominated by spinicaudatans, likely indicating periods when the depositional water body was ephemeral, isolated, or subjected to other difficult environmental conditions. The biota of the Kockatea Shale is insufficiently known to estimate biotic diversity and relationships of individual taxa to their Permian progenitors and Triassic successors, but provides a glimpse into a coastal-zone from the interior of eastern Gondwana. Specialist collecting is needed to clarify the taxonomy of many groups, and comparisons to other Lower Triassic sites are required to provide insights into the pattern of biotic decline and recovery at the end-Permian crisis.