39,768 research outputs found
Development of the City Public Service Model on the Basis of Integrated Transport Flow Indicators
The problem of modeling public services based on architectural and planning decisions is considered, the role of traffic in the formation of a model of city services is analyzed. An integrated criterion for the quality of public services is proposed. A method has been developed for determining segmented public services taking into account the transport areas of the city, which will make it possible to evenly disperse public service centers. The basis is a socio-planning organization, as a material-spatial system containing anthropogenic and natural components – the territory and institutions where the functional processes that take place in the urban planning environment take place. The described model has certain versatility, and is simultaneously suitable for characterizing various categories of service institutions. Thus, the task of optimizing the quality of public services in the city is reduced to a mathematical model for which, by setting the basic design criteria, the optimal result can be obtained.On the basis of a questionnaire survey and analysis of statistical data, calculation of traffic intensity, the demand and supply of the level of public services фre studied. The structural elements of this model: population, territory, transport and service institutions, are in dialectical interaction, which is described by the mathematical model in this study. The model is based on the calculation of the minimum population in the service area, which allows to have i-th type establishments using the social potential method, as well as a graph-analytical method in determining the optimal location of service institutions in the city.As a result of the research, a conceptual model of public services for cities is built, a layout of supermarkets in the territory of Uzhhorod and distribution of service areas of these institutions is proposed. This optimization will ensure uniform domestic servicing of the territory, optimal performance indicators of service establishments and minimum average service radii of points
Optimizing public transit quality and system access: the multiple-route, maximal covering/shortest-path problem
Public transit service is a promising travel mode because of its potential to address urban sustainability. However, current ridership of public transit is very low in most urban regions -- particularly those in the United States. Low transit ridership can be attributed to many factors, among which poor service quality is key. Transit service quality may potentially be improved by decreasing the number of service stops, but this would be likely to reduce access coverage. Improving transit service quality while maintaining adequate access coverage is a challenge facing public transit agencies. In this paper we propose a multiple-route, maximal covering/shortest-path model to address the trade-off between public transit service quality and access coverage in an established bus-based transit system. The model is applied to routes in Columbus, Ohio. Results show that it is possible to improve transit service quality by eliminating redundant or underutilized service stops.
Mixed Polling with Rerouting and Applications
Queueing systems with a single server in which customers wait to be served at
a finite number of distinct locations (buffers/queues) are called discrete
polling systems. Polling systems in which arrivals of users occur anywhere in a
continuum are called continuous polling systems. Often one encounters a
combination of the two systems: the users can either arrive in a continuum or
wait in a finite set (i.e. wait at a finite number of queues). We call these
systems mixed polling systems. Also, in some applications, customers are
rerouted to a new location (for another service) after their service is
completed. In this work, we study mixed polling systems with rerouting. We
obtain their steady state performance by discretization using the known pseudo
conservation laws of discrete polling systems. Their stationary expected
workload is obtained as a limit of the stationary expected workload of a
discrete system. The main tools for our analysis are: a) the fixed point
analysis of infinite dimensional operators and; b) the convergence of Riemann
sums to an integral.
We analyze two applications using our results on mixed polling systems and
discuss the optimal system design. We consider a local area network, in which a
moving ferry facilitates communication (data transfer) using a wireless link.
We also consider a distributed waste collection system and derive the optimal
collection point. In both examples, the service requests can arrive anywhere in
a subset of the two dimensional plane. Namely, some users arrive in a
continuous set while others wait for their service in a finite set. The only
polling systems that can model these applications are mixed systems with
rerouting as introduced in this manuscript.Comment: to appear in Performance Evaluatio
The posssibilities of railway transport utilizing as a backbone network of integrated passenger transport systems
The aspects of utilizing of railway transport as a backbone network of integrated passenger transport systems are solved in the contribution. The basic requirements on this railway transport service
are specified in the contribution. The main attention is focused on creating of line structure of the integrated transport systems. The location of interchange points is also accented in the contribution. The theoretical presumptions are also illustrated in the way of convenient practical examples
Workload Equity in Vehicle Routing Problems: A Survey and Analysis
Over the past two decades, equity aspects have been considered in a growing
number of models and methods for vehicle routing problems (VRPs). Equity
concerns most often relate to fairly allocating workloads and to balancing the
utilization of resources, and many practical applications have been reported in
the literature. However, there has been only limited discussion about how
workload equity should be modeled in VRPs, and various measures for optimizing
such objectives have been proposed and implemented without a critical
evaluation of their respective merits and consequences.
This article addresses this gap with an analysis of classical and alternative
equity functions for biobjective VRP models. In our survey, we review and
categorize the existing literature on equitable VRPs. In the analysis, we
identify a set of axiomatic properties that an ideal equity measure should
satisfy, collect six common measures, and point out important connections
between their properties and those of the resulting Pareto-optimal solutions.
To gauge the extent of these implications, we also conduct a numerical study on
small biobjective VRP instances solvable to optimality. Our study reveals two
undesirable consequences when optimizing equity with nonmonotonic functions:
Pareto-optimal solutions can consist of non-TSP-optimal tours, and even if all
tours are TSP optimal, Pareto-optimal solutions can be workload inconsistent,
i.e. composed of tours whose workloads are all equal to or longer than those of
other Pareto-optimal solutions. We show that the extent of these phenomena
should not be underestimated. The results of our biobjective analysis are valid
also for weighted sum, constraint-based, or single-objective models. Based on
this analysis, we conclude that monotonic equity functions are more appropriate
for certain types of VRP models, and suggest promising avenues for further
research.Comment: Accepted Manuscrip
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