1. Designing efficient algorithms for logistics management : optimizing timeconstrained vehicle routingKarlo Bala, Martin Fale, Nebojša Gvozdenović, Tomaž Kramberger, Dejan Brcanov, 2025, original scientific article Abstract: Background: City logistics is a critical component of urban economic development, as it optimizes supply chains, enhances customer satisfaction through reliable deliveries, and minimizes environmental impacts in densely populated areas. This field addresses various challenges, including traffic congestion, environmental concerns, noise pollution, and the crucial need for timely deliveries. Routing and scheduling are central to logistics operations, with modern software integrating time windows to meet precise scheduling demands driven by detailed customer requirements and operational efficiencies. Furthermore, advanced vehicle routing models now effectively simulate real-world factors such as traffic congestion, stochastic travel times, and dynamic product demands. Purpose: This paper aims to develop an algorithm that addresses the routing decisions. Our approach extends to the time dimension, considering travel times and customer service times within predefined time windows. Study design/methodology/approach: The proposed algorithm is structured to execute in iterative phases, aiming to optimize key logistical objectives. In order to generate competitive solutions, we seek to minimize the number of vehicles utilized and overall travel costs. The evaluation of solution space was conducted via Simulated Annealing. Findings/conclusions: The performance of the proposed algorithm, evaluated using the Gehring and Homberger benchmark instances for 200 customers, demonstrates its effectiveness. The algorithm successfully meets the target number of vehicles required, and the associated travel costs are on average within 1% of the best solutions reported in the relevant literature. Limitations/future research: Given the ongoing need for timely solutions from decision-makers, future research endeavors will focus on enhancing the computational efficiency of the algorithm. Additionally, incorporating more time-related features, such as stochastic travel times, could further improve the algorithm's real-time applicability.
Keywords: city logistics, vehicle routing, simulated annealing, time windows, scheduling
Published in DKUM: 27.03.2025; Views: 0; Downloads: 1
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2. Mixed-integer nonlinear programming based optimal time scheduling of construction projects under nonconvex costsRok Cajzek, Uroš Klanšek, 2016, original scientific article Abstract: Optimal project scheduling under nonconvex time-cost relations represents a challenging problem in construction management. The nonconvex time-cost relations may appear in a construction project when several different duration options are available for its activities due to alternative technological processes enabled for their realization or wide accessibility of production resources. The source of nonconvexity of the project scheduling optimization problem can also be the project penalty- or bonus-duration relations arranged within the construction contract. The aim of this paper is to present the mixed-integer nonlinear programming (MINLP) based optimal time scheduling of construction projects under nonconvex costs. For this purpose, the MINLP model was developed and applied. A numerical example from literature and an example of construction project time-cost trade-off analysis under practical nonconvex penalty function are given in the paper to demonstrate advantages of MINLP optimization. The example from literature first presented the capability of the MINLP approach to obtain the optimal solution for difficult, highly combinatorial nonconvex discrete project scheduling problem. Thereupon, the following example revealed that the optimal project time-cost curve may take very nonuniform shape on account of discrete nature of activity direct cost options and nonconvex relation between project duration and total cost. In this way, the presented study intends to provide practitioners with new information from the field of optimization techniques for project scheduling as well as an alternative view on performance of total cost when project duration is changed.
Keywords: extreme environments, construction management, discrete optimization, mixed-integer nonlinear programming, nonconvex costs, time scheduling
Published in DKUM: 12.07.2017; Views: 1577; Downloads: 422
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4. Implementation of hard real-time embedded control systemsMatjaž Colnarič, Domen Verber, Roman Gumzej, Wolfgang A. Halang, 1998, independent scientific component part or a chapter in a monograph Abstract: Although the domain of hard real-time systems has been thoroughly elaborated in the academic sphere, embedded computer control systems - being an important in mechatronic design - are seldom dealt with consistemntly. Often, off-the-shelf computer systems are used, with no guarantee that they will be able to meet the requirements specified. In this paper, a design for embedded control systems is presented. particulary, the paper deals with the hardware architecture and design details, the operating sustem, and the high-level real-time language support. It is shown how estimates of process run-times necessary for schedulability analysis can be acquired on the basis of deterministic behavior of the hardware platform.
Keywords: kontrolni sistemi, realni čas, mikrokontrolerji, programski jeziki, embedded compuer control systems, hard real-time systems, microcontrollers, transputers, earliest-deadline-first scheduling, real-time programming languages
Published in DKUM: 10.07.2015; Views: 1351; Downloads: 104
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