Time-stepping schemes for finite element tidal model computations

A number of temporal procedures for solving the long-wave surface water equations using the finite element method in space are presented and analyzed. The analysis determines the stability of the schemes and the error in wave amplitude and phase that can be expected. The computational efficiency of the various methods is also discussed. The results ofthis analysis indicate types of errors that might be manifested in finite element surface water modeling using the different schemes.     

Estimation of benthic respiration parameters from field data

Seasonal benthic respiration rate observations from Chesapeake Bay and the Patuxent estuary have been used to determine the benthic decay coefficient. Non-linear parameter estimation procedures were employed to delineate the optimal values and associated confidence intervals for the microbial decay and macrofaunal respiration parameters. The results demonstrate that microbial decay of organic detritus on the bottom is a long-term process with a yearly averaged decay coefficient of around k = 0·0056 day^?1 ($\text{τ =}\text{1}\text{k}\text{= 180}\text{day}$).     

Re-interpretation of zircon date in a carbonatite dyke at the Bayan Obo giant REE-Fe-Nb deposit,China

Recent ce-valuation of the dating of the carbonatite dykes associated with the REE-Re-Nb giant deposit at Bayan Obo has     

The Hillarys Transect (3): Optical and chlorophyll relationships across the continental shelf off Perth

An interdisciplinary study of the waters across the continental shelf off Perth, Western Australia, has provided the first detailed climatology of the physical, chemical, optical, and biological processes across the shelf. In support of this work, remote-sensing data were utilised to provide a broad view of the spatial and temporal chlorophyll concentration dynamics, to support in situ observations, and to help “fill the gaps” inherent in in situ point sampling.     

Market‐based control of linear structural systems

To limit the response of structures during external disturbances such as strong winds or large seismic events, structural control systems can be used. In the structural engineering field, attention has been shifted from active control to semi‐active control systems. Unlike active control system devices, semi‐active devices are compact, have efficient power consumption characteristics and are less expensive. As a result, an environment of a large number of actuators and sensors will result, rendering a complex large‐scale dynamic system. Such a system is best controlled by a decentralized approach such as market‐based control (MBC). In MBC, the system is modelled as a market place of buyers and sellers that leads to an efficient allocation of control power. The resulting MBC solution is shown to be locally Pareto optimal. This novel control approach is applied to three linear structural systems ranging from a one‐storey structure to a 20‐storey structure, all controlled by semi‐active hydraulic dampers. It is shown that MBC is competitive in the reduction of structural responses during large seismic loadings as compared to the centralized control approach of the linear quadratic regulation controller. Copyright © 2002 John Wiley & Sons, Ltd.     

Further Characterisation of the 91500 Zircon Crystal

This paper reports the results from a second characterisation of the 91500 zircon, including data from electron probe microanalysis, laser ablation inductively coupled plasma-mass spectrometry (LA-ICP-MS), secondary ion mass spectrometry (SIMS) and laser fluorination analyses. The focus of this initiative was to establish the suitability of this large single zircon crystal for calibrating in situ analyses of the rare earth elements and oxygen isotopes, as well as to provide working values for key geochemical systems. In addition to extensive testing of the chemical and structural homogeneity of this sample, the occurrence of banding in 91500 in both backscattered electron and cathodoluminescence images is described in detail. Blind intercomparison data reported by both LA-ICP-MS and SIMS laboratories indicate that only small systematic differences exist between the data sets provided by these two techniques. Furthermore, the use of NIST SRM 610 glass as the calibrant for SIMS analyses was found to introduce little or no systematic error into the results for zircon. Based on both laser fluorination and SIMS data, zircon 91500 seems to be very well suited for calibrating in situ oxygen isotopic analyses.     

Late Quaternary Water-Level Variations and Vegetation History at Crooked Pond, Southeastern Massachusetts

Sediment cores collected along a transect in Crooked Pond, southeastern Massachusetts, provide evidence of water-level changes between 15,000 cal yr B.P. and present. The extent of fine-grained, detrital, organic accumulation in the basin, inferred from sediment and pollen stratigraphies, varied over time and indicates low water levels between 11,200 and 8000 cal yr B.P. and from ca. 5300 to 3200 cal yr B.P. This history is consistent with the paleohydrology records from nearby Makepeace Cedar Swamp and other sites from New England and eastern Canada and with temporal patterns of regional changes in effective soil moisture inferred from pollen data. The similarities among these records indicate that (1) regional conditions were drier than today when white pine (Pinus strobus) grew abundantly in southern New England (11,200 to 9500 cal yr B.P.); (2) higher moisture levels existed between 8000 and 5500 cal yr B.P., possibly caused by increased meridonal circulation as the influence of the Laurentide ice sheet waned; and (3) drier conditions possibly contributed to the regional decline in hemlock (Tsuga) abundances at 5300 cal yr B.P. Although sea-level rise may have been an influence, moist climatic conditions during the late Holocene were the primary reason for a dramatic rise in water-table elevations.     

A brief overview of the ACEP project: Ecosystem Processes in the KwaZulu-Natal Bight§

This introductory paper lays the basis for this supplementary issue by briefly presenting the state of knowledge on the KwaZulu-Natal (KZN) Bight at the start of this multi-disciplinary, multi-institutional, ship-based research project that ran from 2009 to 2013. The rationale and aims of the project are also described. The project was a major component of the South African Department of Science and Technology’s African Coelacanth Ecosystem Programme (ACEP), which has been prominent in supporting research on the east coast of South Africa and the wider South-West Indian Ocean. Pivotal to this was the RS Algoa, which was made available for two 30-day surveys (winter and summer) in the KZN Bight by the Department of Environmental Affairs. Although some aspects of the bight ecology are known, much of the research is dated and fragmented, and required refreshing and consolidation in order to produce a platform upon which the understanding of the region’s ecosystem functioning could be established. Much of the oceanographic knowledge is also dated, with no dedicated surveys and significant measurements undertaken since 1989. The overarching theme of the KZN Bight project was to examine the relative importance of sources of nutrients to the central KZN coast and how these are taken up and recycled in the ecosystem, and to describe aspects of the benthic biodiversity, which is poorly described in much of this region. An ambitious project, its accessibility to a ship-based research platform and the diverse scientific skills of the participating scientists allowed considerable success, as reflected in the papers that follow.