Vehicle assignment in site-dependent vehicle routing problems with split deliveries
In this paper we consider the problem of vehicle assignment in heterogeneous fleet site-dependent Vehicle Routing Problems (VRP) with split deliveries. In such VRP problems vehicles can have different capacities, fixed and travel costs, and site-dependency constraints limit for every customer a set of vehicles, which can serve it. The Vehicle Assignment Problem (VAP) arises in heuristic and exact algorithms, when vehicles are assigned to all customers or one customer is added to the current vehicle route. The VAP objective is to minimize the total assignment cost while the cost of assigning a vehicle to a customer is computed in some heuristic way. Without split deliveries, when a delivery to a customer cannot be split between two vehicles, the VAP problem is modeled in literature as the Generalized Assignment Problem. We demonstrate that allowing split deliveries reduces the VAP to the Hitchcock Transportation Problem, which can be efficiently solved with Transportation Simplex Methods. We also consider a special case, which is not rare in practice, when all customers are partitioned into classes, where customers have the same set of vehicles able to serve them, and the vehicle sets for these classes form a sequence of nested sets. We show that in this case if the cost per demand unit of assigning a vehicle to a customer depends only on the vehicle, then the VAP problem can be solved by a linear algorithm.
Vehicle Routing Problem is a well-known problem in logistics and transportation. There is a big variety of VRP problems in the literature, as they arise in many real-life situations. It is a NP-hard combinatorial optimization problem and finding an exact optimal solution is practically impossible in real-life formulations. There is an important subclass of VRP, which is called Truck and Trailer Routing Problem. For this class of problems, every vehicle contains truck and, possibly, trailer parts. In this work, Site-Dependent Truck and Trailer Routing Problem with Hard and Soft Time Windows and Split Deliveries are considered. We develop an Iterative Local Search heuristic for solving this problem. The heuristic is based on the local search approach and also allows infeasible solutions. A greedy heuristic is applied to construct an initial solution.
In this paper we develop an iterative insertion heuristic for a site-dependent truck and trailer routing problem with soft and hard time windows and split deliveries. In the considered problem a truck can leave its trailer for unloading or parking, make a truck-subtour to serve truck-customers, and return back to take the trailer. This can be done several times in one route. In our heuristic every route is constructed by sequentially inserting customers to it in the way similar to Solomon’s (1987) approach developed for simple vehicle routes. Our contributions include: heuristic insertion procedure for complex truck and trailer routes with transshipment locations; efficient randomized mechanisms for choosing the first customer for insertion, for making time window violations, and for making split-deliveries; an improvement procedure shifting deliveries in a route to earlier time; an efficient approach dealing with site-dependency feature based on the transportation problem in case of arbitrary intersecting vehicle sets and a fast vehicle assignment procedure in case of nested vehicle sets.
A model for organizing cargo transportation between two node stations connected by a railway line which contains a certain number of intermediate stations is considered. The movement of cargo is in one direction. Such a situation may occur, for example, if one of the node stations is located in a region which produce raw material for manufacturing industry located in another region, and there is another node station. The organization of freight traﬃc is performed by means of a number of technologies. These technologies determine the rules for taking on cargo at the initial node station, the rules of interaction between neighboring stations, as well as the rule of distribution of cargo to the ﬁnal node stations. The process of cargo transportation is followed by the set rule of control. For such a model, one must determine possible modes of cargo transportation and describe their properties. This model is described by a ﬁnite-dimensional system of diﬀerential equations with nonlocal linear restrictions. The class of the solution satisfying nonlocal linear restrictions is extremely narrow. It results in the need for the “correct” extension of solutions of a system of diﬀerential equations to a class of quasi-solutions having the distinctive feature of gaps in a countable number of points. It was possible numerically using the Runge–Kutta method of the fourth order to build these quasi-solutions and determine their rate of growth. Let us note that in the technical plan the main complexity consisted in obtaining quasi-solutions satisfying the nonlocal linear restrictions. Furthermore, we investigated the dependence of quasi-solutions and, in particular, sizes of gaps (jumps) of solutions on a number of parameters of the model characterizing a rule of control, technologies for transportation of cargo and intensity of giving of cargo on a node station.
Event logs collected by modern information and technical systems usually contain enough data for automated process models discovery. A variety of algorithms was developed for process models discovery, conformance checking, log to model alignment, comparison of process models, etc., nevertheless a quick analysis of ad-hoc selected parts of a journal still have not get a full-fledged implementation. This paper describes an ROLAP-based method of multidimensional event logs storage for process mining. The result of the analysis of the journal is visualized as directed graph representing the union of all possible event sequences, ranked by their occurrence probability. Our implementation allows the analyst to discover process models for sublogs defined by ad-hoc selection of criteria and value of occurrence probability
The geographic information system (GIS) is based on the first and only Russian Imperial Census of 1897 and the First All-Union Census of the Soviet Union of 1926. The GIS features vector data (shapefiles) of allprovinces of the two states. For the 1897 census, there is information about linguistic, religious, and social estate groups. The part based on the 1926 census features nationality. Both shapefiles include information on gender, rural and urban population. The GIS allows for producing any necessary maps for individual studies of the period which require the administrative boundaries and demographic information.
Existing approaches suggest that IT strategy should be a reflection of business strategy. However, actually organisations do not often follow business strategy even if it is formally declared. In these conditions, IT strategy can be viewed not as a plan, but as an organisational shared view on the role of information systems. This approach generally reflects only a top-down perspective of IT strategy. So, it can be supplemented by a strategic behaviour pattern (i.e., more or less standard response to a changes that is formed as result of previous experience) to implement bottom-up approach. Two components that can help to establish effective reaction regarding new initiatives in IT are proposed here: model of IT-related decision making, and efficiency measurement metric to estimate maturity of business processes and appropriate IT. Usage of proposed tools is demonstrated in practical cases.