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  • 1
    Electronic Resource
    Electronic Resource
    Stronger Lagrangian bounds by use of slack variables: Applications to machine scheduling problems (1995)
    Springer
    Mathematical programming 70 (1995), S. 173-190 
    Details
    ISSN: 1436-4646
    Keywords: Lagrangian relaxation ; Slack variables ; Scheduling
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: Abstract Lagrangian relaxation is a powerful bounding technique that has been applied successfully to manyNP-hard combinatorial optimization problems. The basic idea is to see anNP-hard problem as an “easy-to-solve” problem complicated by a number of “nasty” side constraints. We show that reformulating nasty inequality constraints as equalities by using slack variables leads to stronger lower bounds. The trick is widely applicable, but we focus on a broad class of machine scheduling problems for which it is particularly useful. We provide promising computational results for three problems belonging to this class for which Lagrangian bounds have appeared in the literature: the single-machine problem of minimizing total weighted completion time subject to precedence constraints, the two-machine flow-shop problem of minimizing total completion time, and the single-machine problem of minimizing total weighted tardiness.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01585935
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  • 2
    Electronic Resource
    Electronic Resource
    Water-soluble proteins of the human red cell membrane (1970)
    Springer
    The journal of membrane biology 3 (1970), S. 156-172 
    Details
    ISSN: 1432-1424
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Summary Procedures were developed for preparation of red cell membranes almost free of hemoglobin but with minimal loss of membrane proteins. Two water-soluble protein fractions are described, each constituting about 25% of the ghost protein. The first is ionically bonded and can be solubilized in water rapidly at pH 7.0 and more slowly at higher ionic strength solutions, with a minimal rate at 20mm. This fraction contains four major components with molecular weights ranging from 30,000 to 48,000. The second fraction can only be solubilized at an appreciable rate if Ca++ is absent and at higher pH (9.0). It is predominantly a single molecular weight component (150,000). It tends to aggregate at higher ionic strength and in the presence of Ca++. Evidence is presented suggesting that the water-soluble proteins are present at the inner face of the membrane. The lipids remain in a water-insoluble residue that contains four major protein components ranging in molecular weight from 30,000 to 100,000. The latter is the predominant component. Only the residue contains the Na+−K+-activated ATPase, the cholinesterase, antigenic activity and most of the sialic acid and carbohydrate. The first water-soluble fraction contains a Mg++-activated ATPase. The extraction of the water-soluble proteins is accompanied by anatomical changes resulting finally in the formation of small membranous vesicles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01868013
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  • 3
    Electronic Resource
    Electronic Resource
    Factors influencing the egg laying of workers in a captive Bombus terrestris colony (1981)
    Springer
    Behavioral ecology and sociobiology 9 (1981), S. 9-14 
    Details
    ISSN: 1432-0762
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary 1. The egg-laying behaviour of Bombus terrestris workers was studied in a captive colony by means of video recordings, in order to determine factors that make workers become egg-laying workers. 2. The size of a worker as a factor determining her to become a laying worker is only important for the workers that are born from the first batch of eggs. The sequence in which workers are born determines which workers are to become egg-laying workers and which are not. 3. Prospective egg-laying workers seek the proximity of the queen for a long period preceding their oviposition and tend not to participate in foraging activities. Workers who are pre-eminent in having interactions with the queen are the first to lay eggs. These workers compete with the queen for opportunities to lay eggs and finally push the queen off the comb. 4. There is strong competition between workers with regard to the acquisition of opportunities to lay eggs. As the ovaries of the workers develop, the interactions between workers and between workers and the queen become more openly agonistic. Egg-laying workers inhibit oogenesis in younger workers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00299847
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  • 4
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    Development and validation of the global map of irrigation areas (2005)
    Copernicus
    Details
    Publication Date: 2005-11-16
    Description: A new version of a digital global map of irrigation areas was developed by combining irrigation statistics for 10 825 sub-national statistical units and geo-spatial information on the location and extent of irrigation schemes. The map shows the percentage of each 5 arc minute by 5 arc minute cell that was equipped for irrigation around the year 2000. It is thus an important data set for global studies related to water and land use. This paper describes the data set and the mapping methodology and gives, for the first time, an estimate of the map quality at the scale of countries, world regions and the globe. Two indicators of map quality were developed for this purpose, and the map was compared to irrigated areas as derived from two remote sensing based global land cover inventories.
    Print ISSN: 1027-5606
    Electronic ISSN: 1607-7938
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 5
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    Groundwater use for irrigation – a global inventory (2010)
    Copernicus
    Details
    Publication Date: 2010-10-12
    Description: Irrigation is the most important water use sector accounting for about 70% of the global freshwater withdrawals and 90% of consumptive water uses. While the extent of irrigation and related water uses are reported in statistical databases or estimated by model simulations, information on the source of irrigation water is scarce and very scattered. Here we present a new global inventory on the extent of areas irrigated with groundwater, surface water or non-conventional sources, and we determine the related consumptive water uses. The inventory provides data for 15 038 national and sub-national administrative units. Irrigated area was provided by census-based statistics from international and national organizations. A global model was then applied to simulate consumptive water uses for irrigation by water source. Globally, area equipped for irrigation is currently about 301 million ha of which 38% are equipped for irrigation with groundwater. Total consumptive groundwater use for irrigation is estimated as 545 km3 yr−1, or 43% of the total consumptive irrigation water use of 1277 km3 yr−1. The countries with the largest extent of areas equipped for irrigation with groundwater, in absolute terms, are India (39 million ha), China (19 million ha) and the USA (17 million ha). Groundwater use in irrigation is increasing both in absolute terms and in percentage of total irrigation, leading in places to concentrations of users exploiting groundwater storage at rates above groundwater recharge. Despite the uncertainties associated with statistical data available to track patterns and growth of groundwater use for irrigation, the inventory presented here is a major step towards a more informed assessment of agricultural water use and its consequences for the global water cycle.
    Print ISSN: 1027-5606
    Electronic ISSN: 1607-7938
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 6
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    Water resources trends in Middle East and North Africa towards 2050 (2012)
    Copernicus
    Details
    Publication Date: 2012-09-03
    Description: Changes in water resources availability can be expected as consequences of climate change, population growth, economic development and environmental considerations. A two-stage modeling approach is used to explore the impact of these changes in the Middle East and North Africa (MENA) region. An advanced, physically based, distributed, hydrological model is applied to determine the internal and external renewable water resources for the current situation and under future changes. Subsequently, a water allocation model is used to combine the renewable water resources with sectoral water demands. Results show that total demand in the region will increase to 393 km3 yr−1 in 2050, while total water shortage will grow to 199 km3 yr−1 in 2050 for the average climate change projection, an increase of 157 km3 yr−1. This increase in shortage is the combined impact of an increase in water demand by 50% with a decrease in water supply by 12%. Uncertainty, based on the output of the nine GCMs applied, reveals that expected water shortage ranges from 85 km3 yr−1 to 283 km3 yr−1~in 2050. The analysis shows that 22% of the water shortage can be attributed to climate change and 78% to changes in socio-economic factors.
    Print ISSN: 1027-5606
    Electronic ISSN: 1607-7938
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 7
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    Groundwater use for irrigation – a global inventory (2010)
    Copernicus
    Details
    Publication Date: 2010-06-28
    Description: Irrigation is the most important water use sector accounting for about 70% of the global freshwater withdrawals and 90% of consumptive water uses. While the extent of irrigation and related water uses are reported in statistical databases or estimated by model simulations, information on the source of irrigation water is scarce and very scattered. Here we present a new global inventory on the extent of areas irrigated with groundwater, surface water or non-conventional sources, and we determine the related consumptive water uses. The inventory provides data for 15 038 national and sub-national administrative units. Irrigated area was provided by census-based statistics from international and national organizations. A global model was then applied to simulate consumptive water uses for irrigation by water source. Globally, area equipped for irrigation is currently about 301 million ha of which 38% are equipped for irrigation with groundwater. Total consumptive groundwater use for irrigation is estimated as 545 km3 yr−1, or 43% of the total consumptive irrigation water use of 1 277 km3 yr−1. The countries with the largest extent of areas equipped for irrigation with groundwater, in absolute terms, are India (39 million ha), China (19 million ha) and the United States of America (17 million ha). Groundwater use in irrigation is increasing both in absolute terms and in percentage of total irrigation, leading in places to concentrations of users exploiting groundwater storage at rates above groundwater recharge. Despite the uncertainties associated with statistical data available to track patterns and growth of groundwater use for irrigation, the inventory presented here is a major step towards a more informed assessment of agricultural water use and its consequences for the global water cycle.
    Print ISSN: 1812-2108
    Electronic ISSN: 1812-2116
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 8
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    Modeling water resources trends in Middle East and North Africa towards 2050 (2012)
    Copernicus
    Details
    Publication Date: 2012-04-03
    Description: Changes in water resources availability can be expected as consequences of climate change, population growth, economic development and environmental considerations. A two-stage modeling approach is used to explore the impact of these changes in the Middle East and North Africa (MENA) region. An advanced physical based distributed hydrological model is applied to determine the internal and external renewable water resources for the current situation and under future changes. Subsequently, a water allocation model is used to combine the renewable water resources with sectorial water demands. Results show that total demand in the region will increase to 132 km3 yr−1 in 2050, while total water shortage will grow to 199 km3 yr−1 in 2050 for the average climate change projection; an increase of 157 km3. This increase in shortage is the combined impact of an increase in water demand by 50% with a decrease in water supply by 12%. Uncertainty based on the output of the nine GCMs applied, reveals that expected water shortage ranges from 85 km3 to 283 km3 in 2050. The analysis shows that 22% of the water shortage can be attributed to climate change and 78% to changes in socio-economic factors.
    Print ISSN: 1812-2108
    Electronic ISSN: 1812-2116
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 9
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    GlobWat – a global water balance model to assess water use in irrigated agriculture (2015)
    Copernicus
    Details
    Publication Date: 2015-01-20
    Description: GlobWat is a freely distributed, global soil water balance model that is used by FAO to assess water use in irrigated agriculture; the main factor behind scarcity of freshwater in an increasing number of regions. The model is based on spatially distributed high resolution datasets that are consistent at global level and calibrated against values for Internal Renewable Water Resources, as published in AQUASTAT, FAO's global information system on water and agriculture. Validation of the model is done against mean annual river basin outflows. The water balance is calculated in two steps: first a "vertical" water balance is calculated that includes evaporation from in situ rainfall ("green" water) and incremental evaporation from irrigated crops. In a second stage, a "horizontal" water balance is calculated to determine discharges from river (sub-)basins, taking into account incremental evaporation from irrigation, open water and wetlands ("blue" water). The paper describes methodology, input and output data, calibration and validation of the model. The model results are finally compared with other global water balance models.
    Print ISSN: 1812-2108
    Electronic ISSN: 1812-2116
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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  • 10
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    Spatial evapotranspiration, rainfall and land use data in water accounting – Part 2: Reliability of water acounting results for policy decisions in the Awash Basin (2015)
    Copernicus
    Details
    Publication Date: 2015-01-28
    Description: Water Accounting Plus (WA+) is a framework that summarizes complex hydrological processes and water management issues in river basins. The framework is designed to use satellite-based measurements of land and water variables and processes as input data. A general concern associated with the use of satellite measurements is their accuracy. This study focuses on the impact of the error in remote sensing measurements on water accounting and information provided to policy makers. The Awash Basin in the central Rift Valley in Ethiopia is used as a case study to explore the reliability of WA+ outputs, in the light of input data errors. The Monte Carlo technique was used for stochastic simulation of WA+ outputs over a period of 3 yr. The results show that the stochastic mean of the majority of WA+ parameters and performance indicators are within 5% deviation from the original WA+ values based on one single calculation. Stochastic computation is proposed as a standard procedure for WA+ water accounting because it provides the uncertainty bandwidth for every WA+ output, which is essential information for sound decision-making processes. The majority of WA+ parameters and performance indicators have a coefficient of variation (CV) of less than 20%, which implies that they are reliable and provide consistent information on the functioning of the basin. The results of the Awash Basin also indicate that the utilized flow and basin closure fraction (the degree to which available water in a basin is utilized) have a high margin of error and thus a low reliability. As such, the usefulness of them in formulating important policy decisions for the Awash Basin is limited. Other river basins will usually have a more accurate assessment of the discharge in the river mouth.
    Print ISSN: 1027-5606
    Electronic ISSN: 1607-7938
    Topics: Geography , Geosciences
    Published by Copernicus on behalf of European Geosciences Union.
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