State-space representation of radiation forces in time-domain vessel models     

Erlend Kristiansen  smund Hjulstad  Olav Egeland 《Ocean Engineering》2005,32(17-18):2195-2216

The paper presents a method for generating a new and efficient time-domain formulation of the equations of motion for a vessel with frequency-dependent hydrodynamic coefficients. Previous work on this topic has relied on the use of convolution terms, whereas in this work state-space models are used. This leads to a model formulation that is well suited for controller design and simulation.  相似文献   

Transpiration and evaporation from heather Moorland     

A. C. Miranda  P. G. Jarvis  J. Grace 《Boundary-Layer Meteorology》1984,28(3-4):227-243

The energy balance of an upland heath dominated by heather (Calluna vulgaris) was measured in dry and wet weather. Median values of both transpiration and evaporation rates were ca. 2 mm hr^-1. The median Bowen ratio for the dry canopy was 2.0 and for the wet canopy 0.6. On dry days the median value of the saturation deficit was only 3.8 mb and that of the climatological resistance was 30 s m^-1. The bulk stomatal resistance increased from ca. 50 s m ^-2 in the morning to over 290 s m^-1 in the afternoon with an overall median value of 110 s m^-1. Transpiration from the dry canopy was controlled by a combination of small saturation deficits and large stomatal resistances. The median value of the boundary-layer resistance of the canopy was 22 s m^-1 and was low partly because of a large low-level drag coefficient. Saturation deficits on wet days were close to zero and evaporation of intercepted water proceeded at close to the equilibrium rate, being largely limited by the low fluxes of available energy. The water loss from heather was compared with simulated losses from coniferous forest, herbaceous crops and grassland in the same conditions to evaluate the effects of vegetation on water loss from catchments.Laboratorio de Ecologia, Dept. de Biologia Vegetal, Universidade de Brasilia, 70 910 — Brasila — DF, Brazil.  相似文献   

The potential impact of climate change on Australia's soil organic carbon resources     

Peter R Grace  Wilfred M Post  Kevin Hennessy 《Carbon balance and management》2006,1(1):14-10

Background  

Soil organic carbon (SOC) represents a significant pool of carbon within the biosphere. Climatic shifts in temperature and precipitation have a major influence on the decomposition and amount of SOC stored within an ecosystem and that released into the atmosphere. We have linked net primary production (NPP) algorithms, which include the impact of enhanced atmospheric CO₂ on plant growth, to the SOCRATES terrestrial carbon model to estimate changes in SOC for the Australia continent between the years 1990 and 2100 in response to climate changes generated by the CSIRO Mark 2 Global Circulation Model (GCM).  相似文献   

Narratives in REDD+ benefit sharing: examining evidence within and beyond the forest sector     

Grace Yee Wong  Cecilia Luttrell  Lasse Loft  Anastasia Yang  Thuy Thu Pham  Daisuke Naito 《Climate Policy》2019,19(8):1038-1051

REDD+ was designed globally as a results-based instrument to incentivize emissions reduction from deforestation and forest degradation. Over 50 countries have developed strategies for REDD+, implemented pilot activities and/or set up forest monitoring and reporting structures, safeguard systems and benefit sharing mechanisms (BSMs), offering lessons on how particular ideas guide policy design. The implementation of REDD+ at national, sub-national and local levels required payments to filter through multiple governance structures and priorities. REDD+ was variously interpreted by different actors in different contexts to create legitimacy for certain policy agendas. Using an adapted 3E (effectiveness, efficiency, equity and legitimacy) lens, we examine four common narratives underlying REDD+ BSMs: (1) that results-based payment (RBP) is an effective and transparent approach to reducing deforestation and forest degradation; (2) that emphasis on co-benefits risks diluting carbon outcomes; (3) that directing REDD+ benefits predominantly to poor smallholders, forest communities and marginalized groups helps address equity; and (4) that social equity and gender concerns can be addressed by well-designed safeguards. This paper presents a structured examination of eleven BSMs from within and beyond the forest sector and analyses the evidence to variably support and challenge these narratives and their underlying assumptions to provide lessons for REDD+ BSM design. Our findings suggest that contextualizing the design of BSMs, and a reflexive approach to examining the underlying narratives justifying particular design features, is critical for achieving effectiveness, equity and legitimacy.

Key policy insights

• A results-based payment approach does not guarantee an effective REDD+; the contexts in which results are defined and agreed, along with conditions enabling social and political acceptance, are critical.

• A flexible and reflexive approach to designing a benefit-sharing mechanism that delivers emissions reductions at the same time as co-benefits can increase perceptions of equity and participation.

• Targeting REDD+ to smallholder communities is not by default equitable, if wider rights and responsibilities are not taken into account

• Safeguards cannot protect communities or society without addressing underlying power and gendered relations.

• The narratives and their underlying generic assumptions, if not critically examined, can lead to repeated failure of REDD+ policies and practices.

  相似文献   

Grain‐size variability within a mega‐scale point‐bar system,False River,Louisiana     

Peter D. Clift  Elizabeth D. Olson  Alexandra Lechnowskyj  Mary Grace Moran  Allison Barbato  Juan M. Lorenzo 《Sedimentology》2019,66(2):408-434

Point bars formed by meandering river systems are an important class of sedimentary deposit and are of significant economic interest as hydrocarbon reservoirs. Standard point‐bar models of how the internal sedimentology varies are based on the structure of small‐scale systems with little information about the largest complexes and how these might differ. Here a very large point bar (>25·0 m thick and 7·5 × 13·0 km across) on the Mississippi River (USA) was examined. The lithology and grain‐size characteristics at different parts of the point bar were determined by using a combination of coring and electrical conductivity logging. The data confirm that there is a general fining up‐section along most parts of the point bar, with a well‐defined transition from massive medium‐grained sands below about 9 to 11 m depth up into interbedded silts and fine–medium sand sediment (inclined heterolithic strata). There is also a poorly defined increase in sorting quality at the transition level. Massive medium sands are especially common in the region of the channel bend apex and regions upstream of that point. Downstream of the meander apex, there is much less evidence for fining up‐section. Finer sediment accumulated more readily after the establishment of a compound bar in the later stages of construction, at the terminal apex and in the bar tail. This work implies that the best reservoir sands are likely to be located in the centre of the point bar, deposited in a simple bar system. Reservoir quality decreases towards the bar edge. The early‐stage channel plug is largely composed of coarsening‐upward cycles of silt to clay and is dominated by clay and clayey silt material with poor reservoir characteristics.  相似文献   

River temperature regimes of England and Wales: spatial patterns,inter‐annual variability and climatic sensitivity          下载免费PDF全文

Grace Garner  David M. Hannah  Jonathan P. Sadler  Harriet G. Orr 《水文研究》2014,28(22):5583-5598

Identification of the most sensitive hydrological regions to a changing climate is essential to target adaptive management strategies. This study presents a quantitative assessment of spatial patterns, inter‐annual variability and climatic sensitivity of the shape (form) and magnitude (size) of annual river/stream water temperature regimes across England and Wales. Classification of long‐term average (1989–2006) annual river (air) temperature regime dynamics at 88 (38) stations within England and Wales identified spatially differentiable regions. Emergent river temperature regions were used to structure detailed hydroclimatological analyses of a subset of 38 paired river and air temperature stations. The shape and magnitude of air and water temperature regimes were classified for individual station‐years; and a sensitivity index (SI, based on conditional probability) was used to quantify the strength of associations between river and air temperature regimes. The nature and strength of air–river temperature regime links differed between regions. River basin properties considered to be static over the timescale of the study were used to infer modification of air–river temperature links by basin hydrological processes. The strongest links were observed in regions where groundwater contributions to runoff (estimated by basin permeability) were smallest and water exposure time to the atmosphere (estimated by basin area) was greatest. These findings provide a new large‐scale perspective on the hydroclimatological controls driving river thermal dynamics and, thus, yield a scientific basis for informed management and regulatory decisions concerning river temperature within England and Wales. © 2013 The Authors. Hydrological Processes published by John Wiley & Sons, Ltd.  相似文献   

A novel nuclear forensic tool involving deposit type normalized rare earth element signatures   总被引：1，自引：0，他引：1       下载免费PDF全文

Tyler L. Spano  Antonio Simonetti  Thomas Wheeler  Grace Carpenter  Devonee Freet  Enrica Balboni  Corinne Dorais  Peter C. Burns 《地学学报》2017,29(5):294-305

Identifying the provenance of uranium‐rich materials is a critical objective of nuclear forensic analysis. Rare earth element (REE) distributions within uranium ores are well‐established forensic indicators, but quantifying and correlating trace element signatures for U ores to known deposits has thus far involved intricate statistical analyses. This study reports average chondrite normalized (CN)‐REE signatures for important U deposit types worldwide, which are then employed to evaluate U ore paragenesis using a simple linear regression analysis. This technique provides a straightforward method that can aid in determining the deposit type of U ores based on their REE abundances, and combined with other forensic indicators (e.g. radiogenic isotope signatures) can provide essential provenance information for nuclear materials.  相似文献   

Scenarios for Community-based Approaches to Biodiversity Conservation: a case study from the Wet Tropics,Queensland, Australia     

Petina L. Pert  Kristen J. Williams  Elaine K. Harding  Tony O'Malley  Rowena A. Grace 《The Australian geographer》2010,41(3):285-306

Natural resource management approaches that deliver biodiversity conservation remain elusive, with evidence of a persistent implementation gap between biodiversity science and conservation projects. Scenarios have been identified as potentially useful in addressing the complex issues underlying this implementation gap, but have been infrequently applied to biodiversity conservation. Our paper reports on action co-research to develop, apply and assess the efficacy of scenarios within a community-based natural resource management (CBNRM) approach to biodiversity conservation at Mission Beach, a key site within the globally significant Wet Tropics bioregion. We focused on the capacity of scenarios to address the issues of contested interests and uncertainty, aiming specifically to engage the community to build a cohesive vision. The scenarios' headline messages included a projected substantial loss of habitat in coastal vegetation communities that are highly valued by all stakeholders. Our assessment identified that the use of scenarios fulfilled the intended aims, resulting in a vision for biodiversity conservation that has substantial community support. Three factors contributed to this efficacy of the scenarios: (1) the focus on threat; (2) biodiversity science integration; and (3) simplicity in presentation. Further investigation of the potential of scenarios as tools to overcome the implementation gap in biodiversity conservation is recommended.  相似文献   

ECOLOGICAL CONSEQUENCES OF SOIL EROSION AND SEDIMENTATION     

Grace S. BRUSH 《国际泥沙研究》1999,(2)

IHISTORICALRECORDSSoilerosioniscloselyrelatedtorainfallandgreatlyenhancedbydeforestationforagricultUreandurbansuburbandevelopment.Amongtheeffectsofsoilerosionarethelossoftopsoilandaconsequentdecreaseincropproductivity.Erodedsoilisalsodepositedintoaquaticsystems,thuslesseningwaterqualityandleadingtodepletionoftheaquaticfoodresource.Italsocausessiltationofwaterwaysmakingthemineffectiveforcommercialtransportaswellasincreasingtheriskoffloods.Theimpactofsedimenterosionanddepositiononhumanso…  相似文献   

Spring flux as an indicator of source geomorphology,substrata, and temperature conditions in springs     

Swanson  Susan K.  Graham  Grace E. 《Hydrogeology Journal》2022,30(1):221-229

Hydrogeology Journal - Spring flux (m/s), defined as spring flow (m3/s) divided by the area over which groundwater emerges (m2) at a spring, provides a meaningful way to distinguish between...  相似文献