Robust Regulation of Alkalinity in Highly Uncertain Continuous Anaerobic Digestion Processes     

Víctor Alcaraz‐González  Fabián Azael Fregoso‐Sanchez  Hugo Oscar Mendez‐Acosta  Victor Gonzalez‐Alvarez 《洁净——土壤、空气、水》2013,41(12):1157-1164

In this paper, a multiple‐input multiple‐output (MIMO) model‐based robust control scheme is proposed for the indirect control of both total alkalinity and the ratio (intermediate alkalinity)/(total alkalinity) by regulating volatile fatty acid concentrations and strong ions concentration, while guaranteeing the so‐called operational stability in anaerobic digestion (AD) processes. The proposed MIMO regulator is an adaptive controller derived from an AD model which incorporates the physicochemical equilibrium of the system as well as the use of a robust interval observer to estimate key process bounds that are used in the computation of the control efforts. Numerical simulations were carried out for a number of operating conditions under the most uncertain scenarios. Results showed that the proposed multivariable control law is able to recover the system stability around a pre‐determined set point in the face of parameter uncertainty and load disturbances.  相似文献   

Welcome to our world? Immigration and the reshaping of New Zealand     

Graeme Hugo 《The Australian geographer》2013,44(4):487-489

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Late-glacial to Holocene transition in northern Spain deduced from land-snail shelly accumulations     

Yurena Yanes  Igor Gutiérrez-Zugasti  Antonio Delgado 《Quaternary Research》2012,78(2):373-385

Shells of the helicid Cepaea nemoralis were studied using taphonomic, isotopic and morphometric measurements to estimate late glacial–Holocene (~ 12.1–6.3 cal ka BP) environmental conditions in northern Spain. Higher taphonomic alteration among Holocene shells suggests lower sedimentation rates or higher shell-destruction rates than during glacial conditions. Shells preserved the aragonitic composition despite differing degree of skeleton damage. Shell δ¹³C values were ? 10.3 ± 1.1‰, ? 8.2 ± 2.3‰, and ? 7.3 ± 1.6‰ for modern, Holocene and late-glacial individuals, respectively. Higher δ¹³C values during the late-glacial and some Holocene periods imply higher water stress of C₃ plants and/or higher limestone contribution than today. Intrashell δ¹³C values were higher during juvenile stages suggesting higher limestone ingestion to promote shell growth. Shell δ¹⁸O values were ? 1.1 ± 0.7‰, ? 0.9 ± 0.8‰ and ? 0.1 ± 0.7‰ for modern, Holocene and late-glacial specimens, respectively. A snail flux-balance model suggests that during ~ 12.1 ? 10.9 cal ka BP conditions were drier and became wetter at ~ 8.4 ? 6.3 cal ka BP and today. Intrashell δ¹⁸O profiles reveal that glacial individuals experienced more extreme seasonality than interglacial shells, despite possible larger hibernation periods. Shell size correlated positively with δ¹⁸O values, suggesting that growth rates and ultimate adult size of C. nemoralis may respond to climate fluctuation in northern Spain.  相似文献   

Evolution of anthropogenic and biomass burning emissions of air pollutants at global and regional scales during the 1980�C2010 period     

Claire Granier  Bertrand Bessagnet  Tami Bond  Ariela D��Angiola  Hugo Denier van der Gon  Gregory J. Frost  Angelika Heil  Johannes W. Kaiser  Stefan Kinne  Zbigniew Klimont  Silvia Kloster  Jean-Fran?ois Lamarque  Catherine Liousse  Toshihiko Masui  Frederik Meleux  Aude Mieville  Toshimasa Ohara  Jean-Christophe Raut  Keywan Riahi  Martin G. Schultz  Steven J. Smith  Allison Thompson  John van Aardenne  Guido R. van der Werf  Detlef P. van Vuuren 《Climatic change》2011,109(1-2):163-190

Several different inventories of global and regional anthropogenic and biomass burning emissions are assessed for the 1980?C2010 period. The species considered in this study are carbon monoxide, nitrogen oxides, sulfur dioxide and black carbon. The inventories considered include the ACCMIP historical emissions developed in support of the simulations for the IPCC AR5 assessment. Emissions for 2005 and 2010 from the Representative Concentration Pathways (RCPs) are also included. Large discrepancies between the global and regional emissions are identified, which shows that there is still no consensus on the best estimates for surface emissions of atmospheric compounds. At the global scale, anthropogenic emissions of CO, NO_x and SO₂ show the best agreement for most years, although agreement does not necessarily mean that uncertainty is low. The agreement is low for BC emissions, particularly in the period prior to 2000. The best consensus is for NO_x emissions for all periods and all regions, except for China, where emissions in 1980 and 1990 need to be better defined. Emissions of CO need better quantification in the USA and India for all periods; in Central Europe, the evolution of emissions during the past two decades needs to be better determined. The agreement between the different SO₂ emissions datasets is rather good for the USA, but better quantification is needed elsewhere, particularly for Central Europe, India and China. The comparisons performed in this study show that the use of RCP8.5 for the extension of the ACCMIP inventory beyond 2000 is reasonable, until more global or regional estimates become available. Concerning biomass burning emissions, most inventories agree within 50?C80%, depending on the year and season. The large differences between biomass burning inventories are due to differences in the estimates of burned areas from the different available products, as well as in the amount of biomass burned.  相似文献   

Comparative hydrochemistry of five nested catchments located in the upper part of the Barcés river watershed (A Coruña,NW Spain)     

J. Delgado  R. Juncosa  H. Hernández  I. Falcón  A. Vázquez 《Applied Geochemistry》2011

259 stream water and 21 bulk precipitation samples have been studied between April 2008 and December 2010 in order to assess baseline hydrochemical conditions in a rural area of NW Spain. Stream waters are related to five nested catchments (<10 km²) with apparent low mean residence times. Their hydrochemical characteristics are closely related to bulk precipitation although clear evidences of seasonal (flushing, dilution, sediment desorption, etc.), lithological (schist vs. granite substrate) and anthropogenic (land use, contamination) effects are also described.  相似文献   

Measuring the accessibility of different household income groups to basic community services in upland Misamis Oriental,Northern Mindanao,Philippines     

Marc Elgin M. Delgado  Frank Canters 《Singapore journal of tropical geography》2011,32(2):168-184

Improving household accessibility to basic community services can help reduce poverty in upland areas. In this study, spatial analysis with GIS was used to measure the accessibility of different household income groups to community services in the landlocked upland municipality Claveria in Northern Mindanao, the Philippines. Important community services were identified through villagers' participation in a matrix‐scoring activity. Travel information was derived from key informant interviews while the geographical coordinates of sample households and important services were collected using GPS receivers. The Flowmap GIS software (version 7.2) was used to compute accessibility to services along the road network by habal‐habal (two‐wheel motorcycle). Outcomes from the participatory data gathering activities revealed that agricultural, educational and health facilities, as well as government services are important to the community to achieve sustainable livelihoods. Because local people perceive accessibility in terms of monetary costs, rather than distance, road distance measurements were converted into fare costs. Results of the accessibility analysis show that higher‐income household groups generally incur lower mean one‐way travel costs to reach important community services than poorer households. However, almost all households spend more than the daily per capita poverty threshold for the province to reach basic community services. A scenario to improve accessibility to services in the study area was investigated to emphasize the potential of GIS‐based accessibility analysis in rural service planning.  相似文献   

Vegetation Dynamics in a Tidal Freshwater Wetland: A Long-Term Study at Differing Scales     

Christopher W. Swarth  Patricia Delgado  Dennis F. Whigham 《Estuaries and Coasts》2013,36(3):559-574

Tidal freshwater wetlands are complex, species-rich ecosystems located at the interface between tidal estuaries and nontidal rivers. This study conducted on the Patuxent River estuary in Maryland was designed to assess vegetation dynamics over several decades to determine if there were directional changes in the dominant communities. Aerial photographs (1970, 1989, and 2007) documented broad-scale spatial changes in major plant communities. The coverage of areas dominated by Nuphar lutea and Phragmites australis expanded; mixed vegetation and scrub–shrub habitats were essentially unchanged; and Typha and Zizania aquatica communities fluctuated in coverage. Data collected between 1988 and 2010 from permanent plots and transects were used to examine fine-scale changes. Shifts in the importance of some species through time were observed, but there were no directional changes in community species composition. The lack of directional change as measured at a fine scale is characteristic of tidal freshwater wetlands in which variations in the abundance of individual species, especially annuals, are responsible for most short-term change in species composition. Changes in the composition of plant communities are interpreted as responses to variations in vertical accretion, stability of habitat types, invasive plant species, and herbivores. In the future, vegetation changes are likely to occur as a result of the intrusion of brackish water and increased flooding associated with global climate change and sea level rise. This long-term study establishes a baseline from which potential future changes to tidal freshwater wetlands can be better understood.  相似文献   

Sustainability of a Tidal Freshwater Marsh Exposed to a Long-term Hydrologic Barrier and Sea Level Rise     

P. Delgado  P. F. Hensel  C. W. Swarth  M. Ceroni  R. Boumans 《Estuaries and Coasts》2013,36(3):585-594

A 115-year-old railroad levee bisecting a tidal freshwater marsh perpendicular to the Patuxent River (Maryland) channel has created a northern, upstream marsh and a southern, downstream marsh. The main purpose of this study was to determine how this levee may affect the ability of the marsh system to gain elevation and to determine the levee’s impact on the marsh’s long-term sustainability to local relative sea level rise (RSLR). Previously unpublished data from 1989 to 1992 showed that suspended solids and short-term sediment deposition were greater in the south marsh compared to the north marsh; wetland surface elevation change data (1999 to 2009) showed significantly higher elevation gain in the south marsh compared to the north (6?±?2 vs. 0?±?2 mm year^?1, respectively). However, marsh surface accretion (2007 to 2009) showed no significant differences between north and south marshes (23?±?8 and 26?±?7 mm year^?1, respectively), and showed that shallow subsidence was an important process in both marshes. A strong seasonal effect was evident for both accretion and elevation change, with significant gains during the growing season and elevation loss during the non-growing season. Sediment transport, deposition and accretion decreased along the intertidal gradient, although no clear patterns in elevation change were recorded. Given the range in local RSLR rates in the Chesapeake Bay (2.9 to 5.8 mm year^?1), only the south marsh is keeping pace with sea level at the present time. Although one would expect the north marsh to benefit from high accretion of abundant riverine sediments, these results suggest that long-term elevation gain is a more nuanced process involving more than riverine sediments. Overall, other factors such as infrequent episodic coastal events may be important in allowing the south marsh to keep pace with sea level rise. Finally, caution should be exercised when using data sets spanning only a couple of years to estimate wetland sustainability as they may not be representative of long-term cumulative effects. Two years of data do not seem to be enough to establish long-term elevation change rates at Jug Bay, but instead a decadal time frame is more appropriate.  相似文献   

Periodic orbits in the restricted four-body problem with two equal masses     

Jaime Burgos-García  Joaquín Delgado 《Astrophysics and Space Science》2013,345(2):247-263

The restricted (equilateral) four-body problem consists of three bodies of masses m ₁, m ₂ and m ₃ (called primaries) lying in a Lagrangian configuration of the three-body problem i.e., they remain fixed at the apices of an equilateral triangle in a rotating coordinate system. A massless fourth body moves under the Newtonian gravitation law due to the three primaries; as in the restricted three-body problem (R3BP), the fourth mass does not affect the motion of the three primaries. In this paper we explore symmetric periodic orbits of the restricted four-body problem (R4BP) for the case of two equal masses where they satisfy approximately the Routh’s critical value. We will classify them in nine families of periodic orbits. We offer an exhaustive study of each family and the stability of each of them.  相似文献   

Shear effects on hollow section piers under seismic actions: experimental and numerical analysis   总被引：1，自引：0，他引：1  

Raimundo Delgado  Pedro Delgado  Nelson Vila Pouca  António Arêde  Patrício Rocha  Aníbal Costa 《Bulletin of Earthquake Engineering》2009,7(2):377-389

Shear effects are often a very important issue on the seismic behaviour of piers, particularly for hollow section bridge piers. In fact, for this type of piers the cyclic response is similar to that of a structural wall in which both the transverse reinforcement ratio and the detailing can play an important role on its performance, even likely to be determinant in terms of the failure mechanism. On the other hand, codes and design guidelines are usually very conservative concerning shear capacity in order to avoid any shear failure mechanism likely to trigger well known catastrophic consequences. Therefore, research studies on this topic are still needed for a better understanding of pier cyclic shear response and also for improvement of the performance under seismic actions. Pursuing this general objective, this paper partially reports on an experimental/numerical campaign carried out on 1:4 reduced scale bridge piers in order to highlight and investigate shear-type problems. Within the scope of this paper, two specimens types were selected having equal rectangular hollow section (900 × 450 mm², 75 mm thick) but different transverse reinforcement detailing, namely one with a single stirrup per wall (representative of typical bridge construction without seismic design requirements) and another with multiple stirrups, according to Eurocode 8 provisions. Numerical simulations of the experimental results were also conducted aiming at contributing for complete and consistent interpretations of experimental results. Detailed modelling was performed allowing for realistic simulations of the non linear behaviour, particularly suitable when a significant shear component is involved. Therefore, the numerical strategy was based on a detailed 3D FEM discretization using a two-scalar variable damage model for the concrete constitutive law and a suitable cyclic behaviour law for steel bars represented by truss elements. Results have shown that shear deformation and failure modes are well simulated, while providing detailed insight concerning concrete damage pattern and distribution of yielding on the transverse and longitudinal reinforcement.  相似文献