Circulation of Railway Rolling Stock: A Branch-and-Price Approach

We describe an algorithmic approach to determine an efficient railway rolling stock circulation on a single line or on a set of interacting lines. Given the timetable and the passengers? seat demand, we develop a branch-and-price algorithm that results in an allocation of rolling stock material to the daily trips. In order to efficiently utilize the train units, they can be added to or removed from the trains at some stations along the line. These changes in train composition are subject to several constraints, for example corresponding to the order of the train units within a train. A solution is evaluated based on three criteria, i.e. the service to passengers, the robustness, and the cost of the circulation. The branch-and-price algorithm that we developed is tested on real-life instances from NS Reizigers, the main Dutch operator of passenger trains

Exact and approximation algorithms for the operational fixed interval scheduling problem

The Operational Fixed Interval Scheduling Problem (OFISP) is characterized as the problem of scheduling a number of jobs, each with a fixed starting time, a fixed finishing time, a priority index, and a job class. The objective is to find an assignment of jobs to machines with maximal total priority. The problem is complicated by the restrictions that: (i) each machine can handle only one job at a time, (ii) each machine can handle only jobs from a prespecified subset of all possible job classes, and (iii) preemption is not allowed. It follows from the above that OFISP has both the character of a job scheduling problem and the character of an assignment problem. In this paper we discuss the occurrence of the problem in practice, and we present newly developed exact and approximation algorithms for solving OFISP. Finally, some computational results are shown

A DSS for capacity planning of aircraft maintenance personnel

In this paper we describe a Decision Support System (DSS) that has been developed for the aircraft maintenance department of the Dutch national airline company at the main airport in the Netherlands. The aircraft maintenance department is responsible for carrying out the regular short inspections of aircraft between their arrival at and their consecutive departure from the airport. The main resource of the aircraft maintenance department is its workforce. The DSS that has been developed can be used to support the management of the maintenance department in solving several capacity planning problems related to the size and the composition of the workforce. In this paper we give a description of the capabilities of the DSS. Furthermore, we describe the solution technique that is applied within the DSS for determining the required size and composition of the workforce

Allocation of Railway Rolling Stock for Passenger Trains

For a commercially operating railway company, providing a high level of service for the passengers is of utmost importance. The latter requires a high punctuality of the trains and an adequate rolling stock capacity. Unfortunately, the latter is currently (2002) one of the bottlenecks in the service provision by the main Dutch railway operator NS Reizigers. Especially during the morning rush hours, many passengers cannot be transported according to the usual service standards due to a shortage of the ro

α-C-H Photoalkylation of a Glucose Derivative in Continuous Flow

Site-selective photoalkylation is a powerful strategy to extend the carbon framework of carbohydrates, otherwise often attainable only through laborious syntheses. This work describes the adaptation and upscaling of the photoalkylation of a glucose derivative as a continuous flow process. The reported iridium catalyst is replaced by an organic sensitizer and the reaction has been carried out on 40-gram scale

Planning the Size and Organization of KLM's Aircraft Maintenance Personnel

Develops a decision support system (DSS) for the aircraft maintenance department of KLM Royal Dutch Airlines at Schiphol Airport in Amsterdam, Netherlands. Tasks of the department; Support provided by the DSS to management; Analyzing several capacity planning problems related to the size and the organization of the workforce

Routing Trains through railway stations: model formulation and algorithms

In this paper we consider the problem of routing trains through railway stations. This problem occurs as a subproblem in a project which the authors are carrying out in cooperation with the Dutch railways. The project involves the analysis of future infrastructural capacity requirements in the Dutch railway network, Part of this project is the automatic generation and evaluation of timetables. To generate a timetable a hierarchical approach is followed: at the upper level in the hierarchy a tentative timetable is generated, taking into account the specific scheduling problems of the trains at the railway stations at an aggregate level. At the lower level in the hierarchy it is checked whether the tentative timetable is feasible with respect to the safety rules and the connection requirements at the stations. To carry out this consistency cheek, detailed schedules for the trains at the railway yards have to be generated. In this paper we present a mathematical model formulation for this detailed scheduling problem, based on the Node Packing Problem (NPP). Furthermore, we describe a solution procedure for the problem, based on a branch-and-cut approach. The approach is tested in an empirical study with data from the station of Zwolle in The Netherlands

Nickelacyclobutanes: Versatile Reactivity and Role as Catalytic Intermediates

Metallacyclobutanes are intermediates in several catalytic cycles such as olefin metathesis and cyclopropanation. Furthermore, nickel is attracting attention as a versatile, earth-abundant metal in developing new homogeneous catalytic transformations. In this context, the current literature on nickelacyclobutanes and their role in catalysis is reviewed. First, catalytic reactions involving a (putative) nickelacyclobutane intermediate are discussed, including cyclopropanations and various transformations of methylenecyclopropane. Second, studies of the stoichiometric reactivity of nickelacyclobutanes relying on their direct observation or even isolation are detailed. In particular, the relationship between the structure of nickelacyclobutanes and their reactivity is highlighted. Finally, future prospects for the development of new catalytic transformations relying on nickelacyclobutane intermediates are briefly outlined

Impact of time interval between multidisciplinary team meeting and intended pancreatoduodenectomy on oncological outcomes

Background: Dutch guidelines indicate that treatment of pancreatic head and periampullary malignancies should be started within 3 weeks of the multidisciplinary team (MDT) meeting. This study aimed to assess the impact of time to surgery on oncological outcomes. Methods: This was a retrospective population-based cohort study of patients with pancreatic head and periampullary malignancies included in the Netherlands Cancer Registry. Patients scheduled for pancreatoduodenectomy and who were discussed in an MDT meeting from May 2012 to December 2016 were eligible. Time to surgery was defined as days between the final preoperative MDT meeting and surgery, categorized in tertiles (short interval, 18 days or less; intermediate, 19–32 days; long, 33 days or more). Oncological outcomes included overall survival, resection rate and R0 resection rate. Results: A total of 2027 patients were included, of whom 677, 665 and 685 had a short, intermediate and long time interval to surgery respectively. Median time to surgery was 25 (i.q.r. 14–36) days. Longer time to surgery was not associated with overall survival (hazard ratio 0⋅99, 95 per cent c.i. 0⋅87 to 1⋅13; P = 0⋅929), resection rate (relative risk (RR) 0⋅96, 95 per cent c.i. 0⋅91 to 1⋅01; P = 0⋅091) or R0 resection rate (RR 1⋅01, 0⋅94 to 1⋅09; P = 0⋅733). Patients with pancreatic ductal adenocarcinoma and a long time interval had a lower resection rate (RR 0⋅92, 0⋅85 to 0⋅99; P = 0⋅029). Discussion: A longer time interval between the last MDT meeting and pancreatoduodenectomy did not decrease overall survival

Trends and predictors of transmitted drug resistance (TDR) and clusters with TDR in a local Belgian HIV-1 epidemic

We aimed to study epidemic trends and predictors for transmitted drug resistance (TDR) in our region, its clinical impact and its association with transmission clusters. We included 778 patients from the AIDS Reference Center in Leuven (Belgium) diagnosed from 1998 to 2012. Resistance testing was performed using population-based sequencing and TDR was estimated using the WHO-2009 surveillance list. Phylogenetic analysis was performed using maximum likelihood and Bayesian techniques. The cohort was predominantly Belgian (58.4%), men who have sex with men (MSM) (42.8%), and chronically infected (86.5%). The overall TDR prevalence was 9.6% (95% confidence interval (CI): 7.7-11.9), 6.5% (CI: 5.0-8.5) for nucleoside reverse transcriptase inhibitors (NRTI), 2.2% (CI: 1.4-3.5) for non-NRTI (NNRTI), and 2.2% (CI: 1.4-3.5) for protease inhibitors. A significant parabolic trend of NNRTI-TDR was found (p = 0.019). Factors significantly associated with TDR in univariate analysis were male gender, Belgian origin, MSM, recent infection, transmission clusters and subtype B, while multivariate and Bayesian network analysis singled out subtype B as the most predictive factor of TDR. Subtype B was related with transmission clusters with TDR that included 42.6% of the TDR patients. Thanks to resistance testing, 83% of the patients with TDR who started therapy had undetectable viral load whereas half of the patients would likely have received a suboptimal therapy without this test. In conclusion, TDR remained stable and a NNRTI up-and-down trend was observed. While the presence of clusters with TDR is worrying, we could not identify an independent, non-sequence based predictor for TDR or transmission clusters with TDR that could help with guidelines or public health measures