1. A time-evolving optimization model for an intermodal distribution supply chain network : a case study at a healthcare companySara Johansson, My Westberg, 2016, magistrsko delo Opis: Enticed by the promise of larger sales and better access to customers, consumer goods compa- nies (CGCs) are increasingly looking to evade traditional retailers and reach their customers directly–with direct-to-customer (DTC) policy. DTC trend has emerged to have major im- pact on logistics operations and distribution channels. It oers significant opportunities for CGCs and wholesale brands to better control their supply chain network by circumventing the middlemen or retailers. However, to do so, CGCs may need to develop their omni-channel strategies and fortify their supply chains parameters, such as fulfillment, inventory flow, and goods distribution. This may give rise to changes in the supply chain network at all strategic, tactical and operational levels.
Motivated by recent interests in DTC trend, this master thesis considers the time-evolving supply chain system of an international healthcare company with preordained configuration. The input is bottleneck part of the company’s distribution network and involves 20% ≠ 25% of its total market. A mixed-integer linear programming (MILP) multiperiod optimization model is developed aiming to make tactical decisions for designing the distribution network, or more specifically, for determining the best strategy for distributing the products from manufacturing plant to primary distribution center and/or regional distribution centers and from them to customers. The company has got one manufacturing site (Mfg), one primary distribution center (PDP) and three dierent regional distribution centers (RDPs) worldwide, and the customers can be supplied from dierent plants with various transportation modes on dierent costs and lead times. The company’s motivation is to investigate the possibility of reduction in distribution costs by in-time supplying most of their demand directly from the plants. The model selects the best option for each customer by making trade-os among criteria involving distribution costs and lead times. Due to the seasonal variability and to account the market fluctuability, the model considers the full time horizon of one year.
The model is analyzed and developed step by step, and its functionality is demonstrated by conducting experiments on the distribution network from our case study. In addition, the case study distribution network topology is utilized to create random instances with random parameters and the model is also evaluated on these instances. The computational experiments on instances show that the model finds good quality solutions, and demonstrate that significant cost reduction and modality improvement can be achieved in the distribution network. Using one-year actual data, it has been shown that the ratio of direct shipments could substantially improve. However, there may be many factors that can impact the results, such as short-term decisions at operational level (like scheduling) as well as demand fluctuability, taxes, business rules etc. Based on the results and managerial considerations, some possible extensions and final recommendations for distribution chain are oered.
Furthermore, an extensive sensitivity analysis is conducted to show the eect of the model’s parameters on its performance. The sensitivity analysis employs a set of data from our case study and randomly generated data to highlight certain features of the model and provide some insights regarding its behaviour.
Ključne besede: optimization, mixed-integer linear programming, supply chain, distribution network, sensitivity analysis
Objavljeno v RUNG: 14.04.2025; Ogledov: 323; Prenosov: 2
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2. Designing the intermodal multiperiod transportation network of a logistic service provider company for container managementTobias Sahlin, 2016, magistrsko delo Opis: Lured by the promise of bigger sales, companies are increasingly looking to raise the volume of international trade. Consequently, the amount of bulk products carried in containers and transported overseas exploded because of the flexibility and reliability of this type of transportation. However, minimizing the logistics costs arising from the container flow management across different terminals has emerged asa major problem that companies and affiliated third-party logistics firms face routinely.
The empty tankcontainer allocation problem occurs in the context of intermodal distribution systems management and transportation operations carried out by logistic service provider companies. This paper considers the time-evolving supply chain system of an international logistic service provider company that transports bulk products loaded in tank containers via road, rail and sea. In such system, unbalanced movements of loaded tank containers forces the company to reposition empty tank containers. The purpose of this paper is to develop a mathematical model that supports tactical decisions for flow management of empty tank containers. The problem involves dispatching empty tank containers of various types to the meet on-time delivery requirements and repositioning the other tank containers to storage facilities, depots and cleaning stations. To this aim, a mixed-integer linear programming (MILP) multiperiod optimization model is developed.
The model is analyzed and developed step by step, and its functionality is demonstrated by conducting experiments on the network from our case study problem, within the boarders of Europe. The case study constitutes three different scenarios of empty tank container allocation. The computational experiments show that the model finds good quality solutions, and demonstrate that cost and modality improvements can be achieved in the network The sensitivity analysis employs a set of data from our case study and randomly selected data to highlight certain features of the model and provide some insights regarding the model’s behavior.
Ključne besede: supply chain, distribution network, repositioning, intermodal transport, sensitivity analysis
Objavljeno v RUNG: 14.04.2025; Ogledov: 1446; Prenosov: 2
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3. Integrating cultural heritage and urban subway infrastructures : spatial distribution, value assessment, and impacts of the Beijing metro line on cultural heritage regional developmentHaisheng Hu, 2025, doktorska disertacija Opis: This research examines the spatial patterns and economic significance of cultural heritage sites along Beijing’s metro lines, with an emphasis on how urban infrastructure influences heritage preservation. Using spatial analysis methods, including the nearest-neighbor index, geographic concentration index, and location entropy, the research identifies patterns in the distribution of cultural heritage sites - such as ancient architecture, industrial heritage, and tombs - particularly concentrated within Beijing’s second ring road.
The study highlights the connectivity provided by key metro lines, including Lines 1, 2, 4, 5, 7, and 8, which link cultural sites in a point distribution pattern. On these premises, the research established a hierarchical framework to evaluate cultural heritage based on proximity to metro stations, with historical and artistic values being the most significant factors.
The findings suggest that heritage sites within one kilometre of metro stations exert more significant influence on their surrounding areas and emphasize the importance of integrating metro infrastructure with cultural heritage preservation. This study contributes to understanding the spatial dynamics of cultural heritage in urban environments, offering a framework for assessing the impact of heritage within contemporary infrastructure systems.
Practically, the study offers insights for urban planners, metro authorities, and cultural preservation bodies, proposing thematic routes along metro lines—such as Line 1 representing a fusion of Chinese and Western cultures and Line 5 emphasizing religious culture—to enhance cultural tourism. It also emphasizes the need for coordinated efforts between stakeholders to balance heritage conservation and urban development for sustainable growth.
Ključne besede: dissertations, linear cultural heritage, national cultural heritage, Beijing, spatial distribution, economic assessment
Objavljeno v RUNG: 31.03.2025; Ogledov: 433; Prenosov: 10
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4. Particle number size distribution statistics at City-Centre Urban Background, urban background, and remote stations in Greece during summerS. Vratolis, Maria I. Gini, Spiros Bezantakos, Iasonas Stavroulas, Nikos Kalivitis, E. Kostenidou, E. Louvaris, D. Siakavaras, George Biskos, Nikolaos Mihalopoulos, 2019, izvirni znanstveni članek Opis: Particle number size distribution measurements were conducted during the summer of 2012 at City-Centre Urban Background (Patras-C), Urban Background (ICE-HT in Patras, DEM in Athens, EPT in Thessaloniki), and Regional Background stations (FIN in Crete). At the City-Centre Urban Background station, the average number distribution had a geometric mean diameter peak approximately at 60 nm and the highest number concentration, whereas at the Regional Background station and the Urban Background stations it displayed a major peak approximately at 100 nm, with the Regional Background station exhibiting the lowest number concentration. The particle number size distribution at each site was divided into size fractions and, based on their diurnal variation and previous studies, we concluded that the main sources for the City-Centre Urban Background station are traffic and the regional background concentration, for the Urban Background stations fresh traffic, aged traffic, cooking and the regional background concentration, and for the Regional Background station local activities (tourism, cooking) and regional background concentration. The median number concentration that is attributed to regional background concentration for the City-Centre Urban Background, the Urban Background and the Regional Background stations are respectively 13, 29 and 45% of the total number concentration. Nucleation events were identified at DEM station, where the newly formed particles accounted for 4% of the total particle concentration for the measurement period in the size range 10–20 nm, EPT, where they accounted for 12%, and FIN, where they accounted for 1%, respectively. New Particle Formation events contribution during summer to Condensation Cloud Nuclei were therefore insignificant in the Eastern Mediterranean. Modal analysis was performed on the number distributions and the results were classified in clusters. At the City-Centre Urban Background station, the cluster-source that dominated number concentration and frequency is related to fresh and aged traffic emissions, at the Urban Background stations aged traffic emissions, while at the Regional Background station number and frequency were dominated by the regional background concentration. Based on cluster analysis, 18% of the median number distribution was due to long range transport at the City-Centre Urban Background site, 37% at the Urban Background sites, and 59% at the Regional Background site. The Flexible Particle Dispersion Model (FLEXPART) was used in order to acquire geographic origin clusters and we concluded that the Etesian flow increases the median regional background number concentration in the Mediterranean basin by a factor of 2.5–4.
Ključne besede: Mediterranean aerosol, particle number size distribution clustering, FLEXPART clustering
Objavljeno v RUNG: 13.05.2024; Ogledov: 1756; Prenosov: 0
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5. Multiple allocation p-hub location problem for content placement in VoD services: a differential evolution based approachSoumen Atta, Goutam Sen, 2020, izvirni znanstveni članek Opis: In video-on-demand (VoD) services, large volumes of digital data are kept at hubs which are spatially distributed over large geographic areas and users are connected to these hubs based on their demands. In this article, we consider a large database of video files, that are pre-partitioned to multiple segments based on the demand patterns of users. These segments are restricted to be located only in hubs. Here, users are allowed to be allocated to multiple hubs and all hubs are assumed to be connected with each other. We jointly decide the location of hubs, the placement of segments to these hubs and then the assignment of users to these hubs as per their demand patterns and finally, we find the optimal paths to route the demands of users for different segments having the objective of minimizing the total routing cost. In this article, a differential evolution (DE) based method is proposed to solve the problem. The proposed DE-based method utilizes an efficient function to evaluate the objective value of a candidate solution to the proposed problem. It also incorporates two problem-specific solution refinement techniques for faster convergence. Instances of the problem are generated from the real world movie database and the proposed method is applied to these instances and the performance is evaluated against the benchmark results obtained from CPLEX.
Ključne besede: Video-on-demand (VoD) services, Content distribution networks, Database segment location, Hub location, Multiple hub allocation, Differential evolution (DE), IBM ILOG CPLEX
Objavljeno v RUNG: 17.04.2023; Ogledov: 2597; Prenosov: 0
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10. Hidden periodicity in Stripe 82 with Saraswati supercluster—a fractal analysisVimal Raj, Mohanachandran Nair Sindhu Swapna, Sankaranarayana Iyer Sankararaman, 2021, izvirni znanstveni članek Opis: The manuscript attempts to explore the periodicity in the distribution of galaxies in the recently
reported Saraswati supercluster and the Stripe 82 region containing it as an example. The report
of 120 Mpc periodicity in the Abell galaxy clusters by power spectrum analysis is the motivation
behind the study. The power spectral analysis across the central part of the Stripe 82 region
shows a periodic variation of 3.09° or 71 Mpc in fractal dimension whereas an average angular
periodicity of 3.45° or 94 Mpc is observed across the Stripe 82 region. This refers to the
periodicity of complexity or cluster density of galaxy distribution. The texture of the distribution
pattern understood through lacunarity analysis indicates a near symmetric distribution. Fractal
dimensions like box-counting dimension, information dimension and correlation dimension are
also found through multifractal analysis. While the information dimension tells about the
distribution density of galactic points, the correlation dimension details the distribution of
galaxies in the neighbourhood
Ključne besede: galaxy distribution, fractal analysis, multifractals, lacunarity, Saraswati supercluster, Stripe 82
Objavljeno v RUNG: 04.07.2022; Ogledov: 2456; Prenosov: 0
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