Scheduling flights at hub airports

In a typical hub airport, incoming flights from many origins feed outgoing flights to many destinations. If an incoming flight is late, outgoing flights which are fed by it may also be delayed eventually. Alternately, planes may leave before some feeding flights arrive, thereby incurring high misconnection penalties. Clearly, if we plan for very long scheduled ground time between the last incoming flight and the first outgoing one, we can reduce the risk of unscheduled delays or misconnections. However, such a schedule may cost the airline too much in terms of idle personnel and equipment and will not be attractive to the passenger either. On the other hand, if we plan for very short scheduled ground time, we run the risk of excessive unscheduled delays, and/or misconnection penalties. In this paper we develop models designed to optimize the scheduled ground time under two pure policies (i) to wait as long as necessary to ensure all connections, and (ii) not to wait at all (i.e., pay misconnection penalties rather than delay penalties). The models can also be applied to similar problems such as express parcel deliveries and ground transportation hubs. Keywords: Scheduling; Air transportation; Airports; Airline schedulingsupported by the NPS Foundation Research Programhttp://archive.org/details/schedulingflight00trieApproved for public release; distribution is unlimited

A DECISION SUPPORT SYSTEM FOR PURCHASING MANAGEMENT OF LARGE PROJECTS

This paper describes a model base Decision Support System (DSS) for purchasing materials and components for large projects. The DSS may be used under two scenarios. Under one scenario, we have a project to execute, and we are looking for a good way to manage the purchasing so as to minimize the expected costs. The decision variable under our control is when and from whom to order each item. Under the other scenario, we are bidding for the project, and wish to assess the costs associated with the purchasing decisions which we should consider before making our bid. In both cases we take into account expected out of pocket costs as well as lateness and/or expediting penalties. The DSS is designed to help us choose the best supplier for each item and schedule the placement of the orders--decisions which are very difficult to make well without such a model base DSS.Information Systems Working Papers Serie

OPTIMAL SCHEDULING OF PURCHASING ORDERS FOR LARGE PROJECTS

The completion of a typical project hinges upon receiving all the purchased components by the time they are scheduled to be used. Some of these components may have long stochastic lead times, so the project manager is tempted to order them ASAP, to avoid the (usual) high penalties associated with delays. (The penalties may be tangible or intangible, but we assume that they can be measured by monetary units.) This in turn may bring about excessive inventory holding costs. Clearly an optimization is called for to minimize the total expected cost of the project. This is achieved by timing the orders optimally, for the one component case as well as for the n component general case.Information Systems Working Papers Serie

Phaseguide assisted liquid lamination for magnetic particle-based assays

We have developed a magnetic particle-based assay platform in which functionalised magnetic particles are transferred sequentially through laminated volumes of reagents and washing buffers. Lamination of aqueous liquids is achieved via the use of phaseguide technology; microstructures that control the advancing air–liquid interface of solutions as they enter a microfluidic chamber. This allows manual filling of the device, eliminating the need for external pumping systems, and preparation of the system requires only a few minutes. Here, we apply the platform to two on-chip strategies: (i) a one-step streptavidin–biotin binding assay, and (ii) a two-step C-reactive protein immunoassay. With these, we demonstrate how condensing multiple reaction and washing processes into a single step significantly reduces procedural times, with both assay procedures requiring less than 8 seconds

Microfluidic 3D cell culture for high throughput screening

There is an urgent need for more physiologically relevant cell culture methods to guide compound selection in pre-clinical stages of the drug development pipeline. This thesis describes the development of the OrganoPlate, a microfluidic platform that enables enhanced physiology in cell culture models by combining 3D cell culture, co-culture and perfusion flow, whilst maintaining ease of use, compatibility and throughput. Phaseguides are capillary pressure barriers that enable microfluidic liquid routing and patterning without the use of membrane or other physical barriers. This technology was further developed to enable complex liquid routing using only a standard pipette Phaseguide technology was implemented for gel patterning in a dedicated 3D cell culture device embedded in a standard 384 wells plate. Each plate contains up to 96 microfluidic networks that enable perfusion culture of extracellular matrix embedded tissues and perfused epithelial or endothelial tubules. The standard dimensions and high quality optical readout allows interrogation of these tissues using high content readers as well as other standard readout equipment. The platform has been used for the culture of a variety of tissue types and disease models by the authors, but has also been adopted by expert and non-expert users across the field. Analytical BioScience