2,093 research outputs found
Cyclodextrins : molecular wheels for supramolecular chemistry / Julia Lock.
No full text"July 2004"Includes copies of publications by the author as appendix.Includes bibliographical references.ix, 181, [26] leaves : ill. (some col.) ; 30 cm.Describes the construction and characterisation of a variety of supramolecular architectures based on cyclodextrins.Thesis (Ph.D.)--University of Adelaide, School of Chemistry and Physics, Discipline of Chemistry, 2005
LOSCO A Ship Lock Scheduling Model
No full textA ship lock scheduling model called LOSCO was developed in order to decrease passage times at locks with two parallel chambers. Three locks were chosen to model, as they are some of the busiest locks of the Netherlands. The Krammersluizen, the Sluizen Hansweert and the Kreekraksluizen. Passage times are not collected at the locks, therefore the model was compared to SIVAK. SIVAK is the standard model for research on locks at Rijkswaterstaat. To schedule vessels in locks three types of choices can be made. Every vessel needs to be assigned to a chamber, the initiation time of locking should be decided and the order of sailing in a chamber should bedefined. By optimising these choices, passage times can be decreased. Optimising is however not straightforward, as the problem is an instance of the job shop scheduling problem. No exact algorithm has been found to solve these problems in a practical amount of time. Therefore the challange is to find a balance in solution quality and the speed of the model when creating a lock scheduling model. In this thesis, four ideas to improve the lock scheduling model by Verstichel were researched. The first idea is to change the resolution of the timesteps. The gain in performance was however not found to weight up against the loss in solution quality for resolution to be useful. The second idea is to drop the first come, first serve constraint that Verstichel created. This idea was also not found to be effective. The third idea is to divide the scheduling problem up into chunks. This is called cut separation. Chunks of around 25 vessels were found to be effective. The fourth and last idea is that of a maximum waiting time. The maximum waiting time makes the performance of the model better and also makes the scheduling model fairer. Data from the year 2016 was used to schedule all lockings. The LOSCO model is effective for reducing the average assage time per vessel with about 3.9 ± 0.12 SE minutes for the Krammersluizen and 2.0 ± 0.14 SE minutes for the Sluizen Hansweert compared to the SIVAK model. At the Kreekraksluizen, the model could not find a solution, as the Kreekraksluizen are a lot busier than the other locks that were tested. At the Kreekraksluizen on average every 7.8 minutes a vessel arrives, whereas at the Krammersluizen and the Sluizen Hansweert respectively every 14.0 and 13.0 minutes a vessel arrives throughout the year. The LOSCO model is only better than SIVAK if the lock is relatively quiet. At the busiest time of the day, typically in the afternoon, SIVAK performs better. The models perform equal at inter arrival times of around 8to 10 minutes. Optimisation on economical value of the vessels was found to be less effective than optimisation on time. Optimisation on time was also found to be fairer. The LOSCO model is a step ahead towards a practical lock scheduling model. In order to achieve a fully practical model, some simplifications need to be expanded. It is recommended to first improve the model before it is applied in practice, as the model is able to outperform SIVAK in some cases, but not in the busiest cases. After this some extra features can be implemented, such as the model dealing with vessel delays and locks with 3 chambers
Lock
No full textThis object was photographed and inventoried during summer 2019 by Julia Conway ('20) and Bailey Cook ('20) as part of a digital curation fellowship.�Please note that the date issued field refers to the date of the digital object's creation. The temporal coverage field contains date information for the actual physical object, when known.General Description: This is a silver heart shaped lock. It has a design of two birds on the front side. The backside has no design. There is a key that is not attached. It says Hansen on the key.Condition Description: Good condition, The lock will not ope
Lock capacity and traffic resistance of locks
No full textLock capacity and traffic resistance are factors which play an important part in the assessment of future traffic through existing locks and in the determination of the number and size of new ones. In this context lock capacity means the maximum quantity of shipping which can be locked per unit of time in the prevailing conditions, if a lock is operating continuously with full chamber(s). The resistance is reflected in the time lost by shipping due to locking. The present publication deals with methods of determining lock capacity and resistance. The methods relate to eargo-carrying inland waterway vessels of the type operating on Western European waterways
Fatigue of steel lock gates
No full textThe Netherlands contains more than 400 hydraulic structures, of which 120 are locks. Inspections carried out since 2010 by Rijkswaterstaat revealed that a number of cracks per lock gate have been found. Based on experience and an evaluation of the photos made during the inspections it is assumed that the cracks occur due to fatigue. At this moment there is no good insight in the fatigue calculation of steel lock gates. The standard EUROCODE 3 used at the moment, has a part dedicated to fatigue strength, but describes that it is only applicable to structures in atmospheric conditions. As lock gates function in (sea) water conditions, it is questionable whether this standard can be used. Another aspect is that there is no guideline how to determine a load spectrum of forces on lock gates. The following topics are covered: a description of the forces on lock gates, a summation of the observations where cracks have been found, which part of the lock gates should be investigated and the standard that should be used and it’s limitations. Two calculations of fatigue damage based on a simplified model of the forces on lock gates are made. The first investigated case is the West lock of Sambeek and the second is the East lock of Terneuzen. For these lock gates the waterlevel spectrum is determined based on the waterlevel measurements of Rijkswaterstaat. From this spectrum a fatigue damage calculation is made. The results of the fatigue damage calculation based on the simplified schematisation of forces on lock gates did not match the fatigue cracks that have been found during the investigations. Some aspects causing this disparity might be that the schematisation of the lock gate is too simplified and the influence of waves is neglected. Another aspect that could influence the fatigue damage is the maintenance. A poor state of the wooden sealing at the back post, the coating layer and/or the cathodic protection system, could result in lower fatigue damage values. All these aspects have a negative influence on the S-N curve. The fatigue damage calculated with a simplified model cannot determine correct fatigue damage values. Therefore a FEM-model should be used to determine the stresses in the lock gate. The stresses in the lock gate itself should be monitored. A lock gate could be fitted with strain gauges to determine the real stresses in the lock gate. These real stresses could be compared with the result of the FEM-model and confirm the reliability of the FEM-model. Research on the influence of the salt and fresh water condition with or without cathodic protection should be done and rules included in the EUROCODE 3 on the influence of salt and fresh water.Hydraulic Engineering StructuresStructural EngineeringCivil Engineering and Geoscience
Strand separation establishes a sustained lock at the Tus-Ter replication fork barrier
No full textThe bidirectional replication of a circular chromosome by many bacteria necessitates proper termination to avoid the head-on collision of the opposing replisomes. In Escherichia coli, replisome progression beyond the termination site is prevented by Tus proteins bound to asymmetric Ter sites. Structural evidence indicates that strand separation on the blocking (nonpermissive) side of Tus-Ter triggers roadblock formation, but biochemical evidence also suggests roles for protein-protein interactions. Here DNA unzipping experiments demonstrate that nonpermissively oriented Tus-Ter forms a tight lock in the absence of replicative proteins, whereas permissively oriented Tus-Ter allows nearly unhindered strand separation. Quantifying the lock strength reveals the existence of several intermediate lock states that are impacted by mutations in the lock domain but not by mutations in the DNA-binding domain. Lock formation is highly specific and exceeds reported in vivo efficiencies. We postulate that protein-protein interactions may actually hinder, rather than promote, proper lock formation.Accepted Author ManuscriptBN/Nynke Dekker LabBN/Cees Dekker LabBN/Martin Depken La
Lock Head Sustainability: A parametric study into the design of lock heads with mitre gates and single leaf gates
No full textIn this research an effort is made to contribute to the goals of the Betonakkoord. This is done by optimising the design of big and bulky structures consisting out of a lot of concrete, namely lock heads. Lock heads are part of the navigation lock. The main research question answered in this thesis is phrased as follows: How can the design of lock heads be optimised to increase the sustainability?Different alternatives have been generated to try to increase the sustainability. Each alternative has been compared to the lock head in Empel to test their feasibility. The following alternatives are considered: Inhomogeneous cross section, Prestressing and Hollow sections. From the alternative study it becomes clear that none of the alternatives are effective. The alternatives show no significant decrease in cost and MKI. Therefore, the alternatives are neglected in the remainder of the research. Based on this conclusion the following question arises: Is it possible to increase the sustainability of a lock head design based on commonly used design rules? In the next step of the research a parametric model is developed in order to answer this question. The parametric model design is based on the rules prescribed by the 'Handboek voor het ontwerpen van Schutsluizen' and the 'Richtlijnen Vaarwegen 2017'. The parametric model takes into account two types of gates, being a single leaf gate and a mitre gate. Again, the lock head in Empel has been used to validate the parametric model. From the parametric model it follows that in general a mitre gate is more cost effective and sustainable than a single leaf gate. This is because a mitre gate is generally shorter than a single leaf gate, so less materials are used and the construction pit can be smaller. Furthermore, the parametric model shows that the global stability check horizontal bearing capacity is a key parameter in the design of a lock head. To account for the horizontal bearing capacity the length and the weight of the lock head are important factors. The next step is to compare the lock head designs from the parametric model with the lock head design in Empel. The lock head design in Empel deviates from the rules prescribed by the 'Handboek voor het ontwerpen van Schutsluizen'. By deviating from the rules a more cost effective and sustainable design is acquired than both the designs from the parametric model. The lock head in Empel is shorter and lighter than the lock head designs from the parametric model. This is due to the fact that the lock head in Empel derives its horizontal bearing capacity from the lock chamber. In order to design a more cost effective and sustainable lock head it is advised to incorporate the lock chamber in the stability calculations. Hereby a shorter lock head can be achieved.Civil Engineering | Structural Engineering | Hydraulic Structure
A late acceptance algorithm for the lock scheduling problem
No full textIn this paper we present a number of (meta-)heuristics for
tackling the lock scheduling problem. The lock scheduling problem is
introduced as the problem of minimising both the water usage of the
lock and the waiting time of all the ships. The performance of several
local search heuristics with the best improving criterion and the late
acceptance criterion is examined. First parameter values for the late
acceptance list length are determined. With these values all heuristics
and criteria are applied to a large test set. From these experiments we
conclude that the performance of the heuristics is increased by the late
acceptance criterion.edition: 1status: Publishe
Online lock scheduling and disruption management
No full textThe Port of Antwerp is the second-largest container port in Europe. The rising demand for container transport requires significant investments in infrastructure projects. Macomi helps the Port of Antwerp to determine the effect of different projects on the throughput of the port using simulation. In this thesis, the aim is to create algorithms for the introduced online variant of the lock scheduling problem which are applicable for a real-time simulation. In addition, an algorithmic approach to recover the existing schedule when a vessel is delayed is required. To achieve these goals, three online lock scheduling algorithms are introduced and tested on realistic problem instances. Their run-time is negligible compared to exact methods and the resulting lock schedules are competitive. Assuming a constant lockage duration during scheduling allows the number of interactions to be reduced significantly with a small decrease in lock schedule quality. The online lock scheduling algorithms could also be applied to the problem of disruption management. The results are comparable to the high-performing adaptive large neighbourhood search meta-heuristic
Technical feasibility of the Tilting Lock: Structural and morphological analysis of the trench required for the Tilting Lock in a case study at the Haringvliet bridge
No full textThe Tilting Lock is an innovative solution for locations where road traffic crosses marine traffic overhead by a bridge. The occurrence of traffic jams at a bridge during the passage of vessels can be reduced by the construction of a Tilting Lock. By 'submerging' the vessels in the Tilting Lock underneath the bridge, the Tilting Lock increases the available air draft for vessels. Due to the Tilting Lock, vessels can pass a fixed bridge span underneath without hindrance for the road traffic on top of the bridge. The main challenge of the Tilting Lock is the large depth that is required for the implementation of the Tilting Lock. Due to the circular shape of the Tilting Lock, excavations are required up to 30 meter below the current bottom surface of the Haringvliet estuary. These large excavations will interfere with the pile foundation of the Haringvliet bridge piers. In the case study, the feasibility of the excavations that are required for the Tilting Lock was evaluated.Civil Engineering and GeosciencesHydraulic EngineeringHydraulic Structure
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