Effective algorithms for integrated scheduling of handling equipment at automated container terminals

In this paper we consider the problem of integrated scheduling of various types of handling equipment at an automated container terminal, where the objective is to minimize the makespan of the schedule. We present a Branch & Bound algorithm that uses various combinatorial lower bounds. Computational experiments show that this algorithm is able to produce optimal or near optimal schedules for instances of practical size in a reasonable time. We also develop a Beam Search heuristic that can be used to tackle very large problem instances. Our experiments show that for such instances the heuristic obtains close to optimal solutions in a reasonable time.AGV's;Container terminal;beam search;branch & bound;scheduling

Dynamic Scheduling of Handling Equipment at Automated Container Terminals

In this paper we consider the problem of integrated scheduling of various types of handling equipment at an automated container terminal in a dynamic environment. This means that the handling times are not known exactly beforehand and that the order in which the different pieces of equipment handle the containers need not be specified completely in advance. Instead, (partial) schedules may be updated when new information on realizations of handling times becomes available. We present an optimization based Beam Search heuristic and several dispatching rules. An extensive computational study is carried out to investigate the performance of these solution methods under different scenarios. The main conclusion is that, in our tests, the Beam Search heuristic performs best on average, but that some of the relatively simple dispatching rules perform almost as good. Furthermore, our study indicates that it is effective important to base a planning on a long horizon with inaccurate data, than to update the planning often in order to take newly available information into account.beam search;dynamic scheduling;container terminal;dispatching rules

Famas-NewCon: A generator program for stacking in the reference case

The FAMAS-Newcon project aims at developing new logistic control structures for a containerterminal capable of handling jumbo container ships within 24 hours. In one of the subprojectsstacking aspects is studied. This report describes a generator model in which on the basis of a global description arrival and departure moments of individual containers are generated for a medium term (15 weeks). The global description consists of a specification of the modal split in terms of containers handled by jumbo's, deepsea, shortsea, rail, barge and trucks, next a specification of the number and type of containers transported by an individual jumbo and deepsea and finally a specification of the dwell time. The output of the generator program is a file with the following container information: arrival and departure times,import/export modality and the import/export ship in case that is a deepsea or jumbo. This file serves as the input of a stacking program which is described in a sequel report. The advantage of this construction is that several stacking strategies can be compared with the same arrival and departures of containers.generator program;stacking;logistic control structures

Effective algorithms for integrated scheduling of handling equipment at automated container terminals

In this paper we consider the problem of integrated scheduling of various types of handling equipment at an automated container terminal, where the objective is to minimize the makespan of the schedule. We present a Branch & Bound algorithm that uses various combinatorial lower bounds. Computational experiments show that this algorithm is able to produce optimal or near optimal schedules for instances of practical size in a reasonable time. We also develop a Beam Search heuristic that can be used to tackle very large problem instances. Our experiments show that for such instances the heuristic obtains close to optimal solutions in a reasonable time

Effective algorithms for integrated scheduling of handling equipment at automated container terminals

In this paper we consider the problem of integrated scheduling of various types of handling equipment at an automated container terminal, where the objective is to minimize the makespan of the schedule. We present a Branch & Bound algorithm that uses various combinatorial lower bounds. Computational experiments show that this algorithm is able to produce optimal or near optimal schedules for instances of practical size in a reasonable time. We also develop a Beam Search heuristic that can be used to tackle very large problem instances. Our experiments show that for such instances the heuristic obtains close to optimal solutions in a reasonable time

Famas-NewCon: A generator program for stacking in the reference case

The FAMAS-Newcon project aims at developing new logistic control structures for a container terminal capable of handling jumbo container ships within 24 hours. In one of the subprojects stacking aspects is studied. This report describes a generator model in which on the basis of a global description arrival and departure moments of individual containers are generated for a medium term (15 weeks). The global description consists of a specification of the modal split in terms of containers handled by jumbo's, deepsea, shortsea, rail, barge and trucks, next a specification of the number and type of containers transported by an individual jumbo and deepsea and finally a specification of the dwell time. The output of the generator program is a file with the following container information: arrival and departure times, import/export modality and the import/export ship in case that is a deepsea or jumbo. This file serves as the input of a stacking program which is described in a sequel report. The advantage of this construction is that several stacking strategies can be compared with the same arrival and departures of containers

Spatial and temporal variations in the incidence of dust storms in Saudi Arabia revealed from in situ observations

This is the final version. Available from the publisher via the DOI in this record.Monthly meteorological data from 27 observation stations provided by the Presidency of Meteorology and Environment (PME) of Saudi Arabia were used to analyze the spatial and temporal distribution of atmospheric dust in Saudi Arabia between 2000 and 2016. These data were used to analyze the effects of environmental forcing on the occurrence of dust storms across Saudi Arabia by considering the relationships between dust storm frequency and temperature, precipitation, and wind variables. We reveal a clear seasonality in the reported incidence of dust storms, with the highest frequency of events during the spring. Our results show significant positive relationships (p < 0.005) between dust storm occurrence and wind speed, wind direction, and precipitation. However, we did not detect a significant relationship with temperature. Our results reveal important spatial patterns, as well as seasonal and inter-annual variations, in the occurrence of dust storms in Saudi Arabia. For instance, the eastern part of the study area experienced an increase in dust storm events over time, especially in the region near Al-Ahsa. Similarly, an increasing trend in dust storms was also observed in the west of the study area near Jeddah. However, the occurrence of dust storm events is decreasing over time in the north, in areas such as Hail and Qaisumah. Overall, the eastern part of Saudi Arabia experiences the highest number of dust storms per year (i.e., 10 to 60 events), followed by the northern region, with the south and the west having fewer dust storm events (i.e., five to 15 events per year). In addition, our results showed that the wind speeds during a dust storm are 15-20 m/s and above, while, on a non-dust day, the wind speeds are approximately 10-15 m/s or lower. Findings of this study provide insight into the relationship between environmental conditions and dust storm occurrence across Saudi Arabia, and a basis for future research into the drivers behind these observed spatio-temporal trends

Evaluating MODIS dust-detection indices over the Arabian Peninsula

Sand and dust storm events (SDEs), which result from strong surface winds in arid and semi-arid areas, exhibiting loose dry soil surfaces are detrimental to human health, agricultural land, infrastructure, and transport. The accurate detection of near-surface dust is crucial for quantifying the spatial and temporal occurrence of SDEs globally. The Arabian Peninsula is an important source region for global dust due to the presence of extensive deserts. This paper evaluates the suitability of five different MODIS-based methods for detecting airborne dust over the Arabian Peninsula: (a) Normalized Difference Dust Index (NDDI); (b) Brightness Temperature Difference (BTD) (31–32); (c) BTD (20–31); (d) Middle East Dust Index (MEDI) and (e) Reflective Solar Band (RSB). We derive detection thresholds for each index by comparing observed values for ‘dust-present’ versus ‘dust-free’ conditions, taking into account various land cover settings and analyzing associated temporal trends. Our results suggest that the BTD (31–32) method and the RSB index are the most suitable indices for detecting dust storms over different land-cover types across the Arabian Peninsula. The NDDI and BTD (20–31) methods have limitations in identifying dust over multiple land-cover types. Furthermore, the MEDI has been found to be unsuitable for detecting dust in the study area across all land-cover types

Spatial and temporal variations in the incidence of dust storms in Saudi Arabia revealed from in situ observations

Monthly meteorological data from 27 observation stations provided by the Presidency of Meteorology and Environment (PME) of Saudi Arabia were used to analyze the spatial and temporal distribution of atmospheric dust in Saudi Arabia between 2000 and 2016. These data were used to analyze the effects of environmental forcing on the occurrence of dust storms across Saudi Arabia by considering the relationships between dust storm frequency and temperature, precipitation, and wind variables. We reveal a clear seasonality in the reported incidence of dust storms, with the highest frequency of events during the spring. Our results show significant positive relationships (p < 0.005) between dust storm occurrence and wind speed, wind direction, and precipitation. However, we did not detect a significant relationship with temperature. Our results reveal important spatial patterns, as well as seasonal and inter-annual variations, in the occurrence of dust storms in Saudi Arabia. For instance, the eastern part of the study area experienced an increase in dust storm events over time, especially in the region near Al-Ahsa. Similarly, an increasing trend in dust storms was also observed in the west of the study area near Jeddah. However, the occurrence of dust storm events is decreasing over time in the north, in areas such as Hail and Qaisumah. Overall, the eastern part of Saudi Arabia experiences the highest number of dust storms per year (i.e., 10 to 60 events), followed by the northern region, with the south and the west having fewer dust storm events (i.e., five to 15 events per year). In addition, our results showed that the wind speeds during a dust storm are 15–20 m/s and above, while, on a non-dust day, the wind speeds are approximately 10–15 m/s or lower. Findings of this study provide insight into the relationship between environmental conditions and dust storm occurrence across Saudi Arabia, and a basis for future research into the drivers behind these observed spatio-temporal trends