1,450 research outputs found
Algorithms for On-line Order Batching in an Order-Picking Warehouse
No full textIn manual order picking systems, order pickers walk or ride through a distribution warehouse in order to collect items required by (internal or external) customers. Order batching consists of combining these – indivisible – customer orders into picking orders. With respect to order batching, two problem types can be distinguished: In off-line (static) batching all customer orders are known in advance. In on-line (dynamic) batching customer orders become available dynamically over time. This report considers an on-line order batching problem in which the total completion time of all customer orders arriving within a certain time period has to be minimized. The author shows how heuristic approaches for the off-line order batching can be modified in order to deal with the on-line situation. A competitive analysis shows that every on-line algorithm for this problem is at least 2-competitive. Moreover, this bound is tight if an optimal batching algorithm is used. The proposed algorithms are evaluated in a series of extensive numerical experiments. It is demonstrated that the choice of an appropriate batching method can lead to a substantial reduction of the completion time of a set of customer orders.Warehouse Management, Order Picking, Order Batching, On-line Optimization
Regulation of non-point phosphorus emissions from the agricultural sector by use of economic incentives
No full textThe thesis consists of four papers all dealing with phosphorus (P) regulation in the agricultural sector from either a theoretic or an empirical approach. Reducing P losses to the aquatic environment is important because P and nitrogen can damage the aquatic system by fuelling excessive algal growth and accelerating eutrophication of lakes and streams. In recent decades loss of P from the agricultural sector has caused eutrophication of streams and lakes across Europe and North America. The sector there seems to be the core of the problem is the intensive and increasing livestock sector which generates manure P well in excess of crop requirements. Because application of manure (and the regulation thereof) is primarily determined by nitrogen crop nutrition, livestock farmers are not motivated to reduce their surplus P applications. Continued application of P in excess of crop requirements causes P stocks to build up in fields and, over time, this increases the risk of losing P to the aquatic environment. The first paper identifies the most important parameters to include in a dynamic model where farm profit is maximized over time whilst taking soil-P dynamics into account. The second paper completes the modelling framework from paper 1 and analyses how a tax on P surpluses motivates the different farmer types to utilize the soil-P stock and implement measures to reduce P loss. The third and fourth papers are empirical, where a farm profit maximization model is developed for an area in the catchment area of Odense Fjord, Denmark. The two papers investigate two different general incentives for reducing soil P losses: a tax on mineral-fertilizer P and a tax on P surplus and a targeted tax on the phosphorus index (PI) for erosion. The PI estimates the risk of P being lost to the environment from critical source areas taking spatial parameters into account. With reference to the joint findings of all four papers it is concluded that a tax on P surplus can be a core element in a close-to-efficient policy regulating P losses from the agricultural sector. However, the general tax fails to regulate high risk areas efficiently and could therefore be supplemented with a targeted policy for implementation of filter strips at high risk fields.<br/
Musgrave Block, SA, 1967 (P338), magnetic line data, AWAGS levelled
No full textMaintenance and Update Frequency: notPlannedStatement: This Musgrave Block, SA, 1967 (P338), magnetic line data, AWAGS levelled is an airborne-derived magnetic line dataset for the Musgrave Block, SA, 1967 survey. The data was acquired under the project No. 338 for the geological survey of SA. A total of 30860 line-kilometres of data at a line spacing of 1600m and 150m terrain clearance were acquired during this survey. To constrain long wavelengths in the data, an independent data set, the Australia-wide Airborne Geophysical Survey (AWAGS) airborne magnetic data, was used to control the base levels of the survey data (Milligan et al., 2009). This survey data is essentially levelled to AWAGS. Details of the specifications of individual airborne surveys can be found in the Fourteenth Edition of the Index of Airborne Geophysical Surveys (Percival, 2014). This Index is also available online at http://pid.geoscience.gov.au/dataset/79134.
References:
Milligan, P.R., Minty, B.R.S., Richardson, M. & Franklin, R., 2009. The Australia-wide Airborne Geophysical Survey accurate continental magnetic coverage. Preview, No. 138, p. 1-128,
Percival, P.J., 2014. Index of airborne geophysical surveys (Fourteenth Edition).Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose.<br/> These line dataset from the Musgrave Block, SA, 1967 survey were acquired in 1967 by the SA Government, and consisted of 30860 line-kilometres of data at 1600m line spacing and 150m terrain clearance. To constrain long wavelengths in the data, an independent data set, the Australia-wide Airborne Geophysical Survey (AWAGS) airborne magnetic data, was used to control the base levels of the survey data. This survey data is essentially levelled to AWAGS
Can non-point phosphorus emissions from agriculture be regulated efficiently using input-output taxes?
No full textIn many parts of Europe and North America, phosphorus loss from cultivated fields is threatening natural ecosystems. Though there are similarities to other non-point agricultural emissions like nitrogen that have been studied extensively, phosphorus is often characterised by the presence of large stocking capacities for phosphorus in farm soils and long time-lags between applications and emission. This makes it important to understand the dynamics of the phosphorus emission problem when designing regulatory systems. Using a model that reflects these dynamics, we evaluate alternative regulatory systems. Depending on the proportions of different types of farms in the agricultural sector, we find that an input-output tax system may be close to efficient, or in other cases must be supplemented with subsidy and manure reallocation schemes.In many parts of Europe and North America, phosphorus loss from cultivated fields is threatening natural ecosystems. Though there are similarities to other non-point agricultural emissions like nitrogen that have been studied extensively, phosphorus is often characterised by the presence of large stocking capacities for phosphorus in farm soils and long time-lags between applications and emission. This makes it important to understand the dynamics of the phosphorus emission problem when designing regulatory systems. Using a model that reflects these dynamics, we evaluate alternative regulatory systems. Depending on the proportions of different types of farms in the agricultural sector, we find that an input-output tax system may be close to efficient, or in other cases must be supplemented with subsidy and manure reallocation schemes
Are CEOs in Family Firms Paid Like Bureaucrats? Evidence from Bayesian and Frequentist Analyses
No full textThe relationship between CEO pay and performance has been much analyzed in the management and economics literature. This study analyzes the structure of executive compensation in family and non-family firms. In line with predictions of agency theory, it is found that the share of base salary is higher with family-member CEOs than it is with nonfamily member CEOs. Furthermore, family-member CEOs receive a lower share of option pay. The paper’s findings have implications for family business research and the executive compensation literature. To make the findings robust, the statistical analysis is performed with both Bayesian and classical frequentist methods.Executive compensation, family firms, stock options, agency theory, Bayesian analysis
Gawler Craton Airborne Survey, Tranche 2, Block 8b, Billa Kalina, 2017 (P1300), elevation line data
No full textMaintenance and Update Frequency: notPlannedStatement: This Gawler Craton Airborne Survey, Tranche 2, Block 8b, Billa Kalina, 2017 (P1300), elevation line data is an airborne-derived elevation data for the Gawler Craton Airborne Survey, Tranche 2, Block 8b, Billa Kalina, 2017. The survey was acquired under the project No. 1300 for the geological survey of SA. A total of 90584 line-kilometres of data at a line spacing of 200m and 60m terrain clearance were acquired during this survey. The elevation data was calculated using the altimeters and Global Positioning System (GPS) sensor used for the benefit airborne of magnetic and radiometric data on the same survey. The elevation is the height relative to the Australian Height Datum GDA94 (AUSGEOID09). Details of the specifications of individual airborne surveys can be found in the Fourteenth Edition of the Index of Airborne Geophysical Surveys (Percival, 2014). This Index is also available online at http://pid.geoscience.gov.au/dataset/79134.
Reference:
Percival, P.J., 2014. Index of airborne geophysical surveys (Fourteenth Edition).The Digital Elevation Model represents ground surface topography between points of known elevation. The elevation data was calculated using the altimeters and Global Positioning System (GPS) sensor used for the benefit of airborne magnetic and radiometric data on the same survey. The elevation is the height relative to the Australian Height Datum GDA94 (AUSGEOID09). The processed elevation data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose.<br/> These line dataset from the Gawler Craton Airborne Survey, Tranche 2, Block 8b, Billa Kalina, 2017 survey were acquired in 2017 by the SA Government, and consisted of 90584 line-kilometres of data at 200m line spacing and 60m terrain clearance
Hodgkinson-Georgetown Block C, QLD, 2000, Prospectivity Plus Init. (P788), elevation line data
No full textMaintenance and Update Frequency: notPlannedStatement: This Hodgkinson-Georgetown Block C, QLD, 2000, Prospectivity Plus Init. (P788), elevation line data is an airborne-derived elevation data for the Hodgkinson-Georgetown Block C, QLD, 2000, Prospectivity Plus Init.. The survey was acquired under the project No. 788 for the geological survey of QLD. A total of 72706 line-kilometres of data at a line spacing between 200m and 400m, and 80m terrain clearance were acquired during this survey. The elevation data was calculated using the altimeters and Global Positioning System (GPS) sensor used for the benefit of airborne magnetic and radiometric data on the same survey. The elevation is the height relative to the Australian Height Datum GDA94 (AUSGEOID09). Details of the specifications of individual airborne surveys can be found in the Fourteenth Edition of the Index of Airborne Geophysical Surveys (Percival, 2014). This Index is also available online at http://pid.geoscience.gov.au/dataset/79134.
Reference:
Percival, P.J., 2014. Index of airborne geophysical surveys (Fourteenth Edition).The Digital Elevation Model represents ground surface topography between points of known elevation. The elevation data was calculated using the altimeters and Global Positioning System (GPS) sensor used for the benefit of airborne magnetic and radiometric data on the same survey. The elevation is the height relative to the Australian Height Datum GDA94 (AUSGEOID09). The processed elevation data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose.<br/> These line dataset from the Hodgkinson-Georgetown Block C, QLD, 2000, Prospectivity Plus Init. survey were acquired in 2000 by the QLD Government, and consisted of 72706 line-kilometres of data at a line spacing between 200m and 400m, and 80m terrain clearance
Can non-point Phosphorus emissions from agriculture be regulated efficiently using input-output taxes?
No full textIn many parts of Europe and North America, phosphorus loss from cultivated fields is threatening natural ecosystems. Though there are similarities to other non-point agricultural emissions like nitrogen that have been studied extensively, phosphorus is often characterized by the presence of large stocking capacities for phosphorus in farm soils and long time-lags between applications and emission. This makes it important to understand the dynamics of the phosphorus emission problem when designing regulatory systems. Using a model that reflects these dynamics, we evaluate alternative regulatory systems. Depending on the proportions of different types of farms in the agricultural sector, we find that an input-output tax system can be the core element of a close to efficient regulatory policy.In many parts of Europe and North America, phosphorus loss from cultivated fields is threatening natural ecosystems. Though there are similarities to other non-point agricultural emissions like nitrogen that have been studied extensively, phosphorus is often characterized by the presence of large stocking capacities for phosphorus in farm soils and long time-lags between applications and emission. This makes it important to understand the dynamics of the phosphorus emission problem when designing regulatory systems. Using a model that reflects these dynamics, we evaluate alternative regulatory systems. Depending on the proportions of different types of farms in the agricultural sector, we find that an input-output tax system can be the core element of a close to efficient regulatory policy
Assessing Moving Block Railway Capacity Based on Fixed Block Infrastructure Occupation
No full textMoving block signalling promises a significant reduction of the infrastructure occupation compared to a fixed block system, such as NS’54/ATB. This is mainly caused by a strong reduction of the approach and running time. However, to assess the capacity gains track occupation data, such as blocking times are needed. ETCS L3 Moving Block is still in development, so gathering data out of daily operations is not possible. Also gathering moving block data out of simulation isn’t always a convenient solution. For example, in simulation software FRISO, used at ProRail, ETCS L3 Moving Block is not (yet) implemented. With infrastructure data, rolling stock parameters and planned time-distance data, blocking times for a moving block signalling system can be estimated. The model presented in this thesis has an average error of 0.87s to the blocking time. In 95% of the cases the error is within a range of (-3,3) seconds. Given that ProRail plans with a precision of 6 seconds, it can be concluded that the model both precise as accurate. With the blocking times of all trains, bottlenecks in both railway corridors and complex nodes can be identified. One could sum all blocking times per block and consider blocks with the highest summed blocking times as bottleneck. However, this can only be applied for homogeneous traffic situations. Another approach is identifying bottlenecks by the shortest buffer time between two trains, also called a critical block. This can be applied for both homogeneous as heterogeneous traffic situations. An advantage is that it is not needed to split corridors into line sections. One could analyse a whole network at once and identify bottleneck at a microscopic level. By keeping the same timetable, the buffer time between two trains increases on average by 75 seconds (60%) using moving block over NS’54.Civil Engineering | Transport and Plannin
Gawler Block (Port Augusta), SA, 1975 (75SA01) (74io) (P426), magnetic line data, AWAGS levelled
No full textMaintenance and Update Frequency: notPlannedStatement: This Gawler Block (Port Augusta), SA, 1975 (75SA01) (74io) (P426), magnetic line data, AWAGS levelled is an airborne-derived magnetic line dataset for the Gawler Block (Port Augusta), SA, 1975 (75SA01) (74io) survey. The data was acquired under the project No. 426 for the geological survey of SA. A total of 12693 line-kilometres of data at a line spacing of 1500m and 150m terrain clearance were acquired during this survey. To constrain long wavelengths in the data, an independent data set, the Australia-wide Airborne Geophysical Survey (AWAGS) airborne magnetic data, was used to control the base levels of the survey data (Milligan et al., 2009). This survey data is essentially levelled to AWAGS. Details of the specifications of individual airborne surveys can be found in the Fourteenth Edition of the Index of Airborne Geophysical Surveys (Percival, 2014). This Index is also available online at http://pid.geoscience.gov.au/dataset/79134.
References:
Milligan, P.R., Minty, B.R.S., Richardson, M. & Franklin, R., 2009. The Australia-wide Airborne Geophysical Survey accurate continental magnetic coverage. Preview, No. 138, p. 1-128,
Percival, P.J., 2014. Index of airborne geophysical surveys (Fourteenth Edition).Total magnetic intensity (TMI) data measures variations in the intensity of the Earth's magnetic field caused by the contrasting content of rock-forming minerals in the Earth crust. Magnetic anomalies can be either positive (field stronger than normal) or negative (field weaker) depending on the susceptibility of the rock. The data are processed via standard methods to ensure the response recorded is that due only to the rocks in the ground. The results produce datasets that can be interpreted to reveal the geological structure of the sub-surface. The processed data is checked for quality by GA geophysicists to ensure that the final data released by GA are fit-for-purpose.<br/> These line dataset from the Gawler Block (Port Augusta), SA, 1975 (75SA01) (74io) survey were acquired in 1975 by the SA Government, and consisted of 12693 line-kilometres of data at 1500m line spacing and 150m terrain clearance. To constrain long wavelengths in the data, an independent data set, the Australia-wide Airborne Geophysical Survey (AWAGS) airborne magnetic data, was used to control the base levels of the survey data. This survey data is essentially levelled to AWAGS
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