Facility Location Research Papers - Academia.edu (original) (raw)

2025, PLOS ONE

2025, verona Univeristy

One of the great challenges in urban planning is determining suitable location for the inhabitants in urban context, the quantitative evaluation of the suitability of urban residential land is essential for a better and more powerful understanding of urban land use planning and improvement. Since the suitable site selection for the residential land use is a risk taking venture and is a highly coordinated effort involving a variety of decisions that are made by a number of individuals, scientific methods must be applied to the process in order to mitigate the level of uncertainty and the initial selection of the most appropriate location. Meanwhile the accumulation of internally displaced persons (IDPs) and returning refugees in Kabul city the capital of Afghanistan has turned the city into a crowded city with limited urban infrastructures and services. In this research, the methodology to select suited settlement locations for population is explained through Analytical Network Process ANP. This study aims to use the Analytical Network Process ANP and Geographic Information System (GIS) as tools to select the best locations to protect a durable solution for the IPDs and Returnees in Kabul city. Various social, economic, environmental, utilities, and physical factors were used to provide a system for supporting the suitable site selection decisions with respect to the selection of pre-defined choices by government for settlements, the best choice is selected, the criteria for analyzing settlements are defined using the literature review and surveying a group of experts and students in the field of urban planning. Results showed that, different criteria's could be applied on the area of interest and all of them are sustainable, but choosing the best deepened on the priority of querying the development sector. The paper suggests an ANP method for the suitable land selection choosing the best location that would be a guide for the governmental authorities in considering into the planning decisions.

2025, Revista Facultad de Ingeniería, Universidad de Antioquia

A model was created to optimize aid relief efforts by identifying the best location to set up shelters. This model, which was developed using a mixed-integer linear program - MILP, considers the availability of resources and the cost of different locations, as well as constraints that must be met to ensure timely aid delivery. A solution involving the use of branch-and-cut algorithm with the help of GeoJSON API and Python code was proposed. Additionally, a study was conducted to assess the impact of the model by analyzing the water supply during a natural disaster in Mocoa, Colombia in 2017. The results of the study showed that the model had a positive impact on reducing the distance resources had to travel, increasing the satisfaction of shelter needs, and decreasing the costs of implementation.

2025, arXiv (Cornell University)

The geometric median, an instrumental component of the secure machine learning toolbox, is known to be effective when robustly aggregating models (or gradients), gathered from potentially malicious (or strategic) users. What is less known is the extent to which the geometric median incentivizes dishonest behaviors. This paper addresses this fundamental question by quantifying its strategyproofness. While we observe that the geometric median is not even approximately strategyproof, we prove that it is asymptotically α-strategyproof : when the number of users is large enough, a user that misbehaves can gain at most a multiplicative factor α, which we compute as a function of the distribution followed by the users. We then generalize our results to the case where users actually care more about specific dimensions, determining how this impacts α. We also show how the skewed geometric medians can be used to improve strategyproofness.

2025

To my late dad, Francis John Gikibi, my hero, for his upbringing, believing in my capabilities and a staunch supporter of the girl child education. I miss you greatly and wish you were around to witness your dreams being fulfilled. Special thanks to my dear Husband Tony, the rock of my life and children Ian and Ivy, my special gifts from God, for their warm support and understanding during my period of study. Deep appreciation goes to my mum, Jerioth Wanjiru and Tata for their continued love, support and wise counsel. To my Gik sisters, Joyce, Rosemary, Alice and Nancy, I am privileged to be one of your sisters and treasure your presence in my life.

2025, Axis Electricals India Pvt Ltd

Our Heat Shrink Tubing Guide covers everything you need to know to select, install, and maximize the performance of heat shrink products. Here’s a quick look at what you will learn: 1 What Are Heat Shrink Products and How Do They Work?... more

2025, Asian Journal of Civil Engineering

Construction projects face many risks that can impact cost, schedule, and quality. To prioritize the most critical risks, a multicriteria decision analysis method like the analytic hierarchy process (AHP) is useful. AHP provides a structured framework to evaluate risks across different criteria and determine their overall priority. This enables focusing risk management efforts on the highest impact risks to cost, time, and quality. Construction projects in Egypt face many risks that can impact cost, schedule, and quality. This research applied a multi-criteria decision analysis method called the analytic hierarchy process (AHP) to identify and prioritize high-impact risks for construction projects in Egypt. The study considered criteria such as cost, time, and quality when evaluating risk factors. Statistical modeling illustrated the process of investigating and identifying the risk factor with the most significant potential impact. The findings indicate that the lack of clear delegation of responsibilities for professionals to allocate activities is the most critical risk factor for construction projects in Egypt. And, effective risk management should focus on mitigating this risk to avoid negative impacts to project performance.

2025, Theoretical Computer Science

Efficient algorithms for solving the center problems in weighted cactus networks are presented. In particular, we have proposed the following algorithms for the weighted cactus networks of size n: an O(n log n) time algorithm to solve the 1-center problem, and an O(n log 3 n) time algorithm to solve the weighted continuous 2-center problem. We have also provided improved solutions to the general p-center problems in cactus networks. The developed ideas are then applied to solve the obnoxious 1-center problem in weighted cactus networks.

2025

In this paper evolutionary methods, specifically genetic algorithms (GAs), are used to demonstrate the application in the determination of the location of a distribution center (DC) in the supply chain. One case is tested, which is a problem with GOUTTE's constrains beginning with its solution by the traditional method implemented in Lingo. We pretend to show the efficacy of applying GAs in the determination of the nearest solution to the optimum as the advantage of this method. The results are compared with optimization deterministic models implemented in traditional software by presenting another alternative of solution with an approximation to the optimum value and lower computational cost. .

2025

This study explores two influential location theories in the field of economic geography and spatial planning: the Central Place Theory by Walter Christaller and the location theory by August Lösch. Christaller's theory emphasizes the hierarchical structure of service centers arranged in a hexagonal spatial pattern, while Lösch offers a more dynamic approach to determining the optimal location for economic activities based on potential maximum profit. This material is intended to provide a conceptual understanding and comparison of both theories, as well as to examine their relevance and application in modern spatial analysis and regional planning.

2025

Ich erkläre hiermit an Eides Statt, daß ich die vorliegende Arbeit selbtständig und ohne Benutzung anderer als der angegebenen Hilfsmittel angefertigt habe. Die aus fremden Quellen direkt oder indirekt übernommenen Gedanken sind als solche kenntlich gemacht. Die Arbeit wurde bisher in gleicher oder ähnlicher Form keiner anderen Prüfungsbehörde vorgelegt und auch noch nicht veröffentlicht. Wien, am 2. Dezember 2013 Nađa Džubur

2025, Computers & Industrial Engineering

2025, International Journal of Scientific & Technology Research

There are two types of Facility Location Problem (FLP) that have been presented. The first type of FLP is minisum rectilinear distance single FLP which have been solved by using median method and also linear programming formulation which solved by using linear programming software, TORA. The second type of FLP is minisum Euclidean distance single FLP which solved by using Weiszfeld’s method and also extension of Weiszfeld’s method. Given weighted demand points, the new facility location point was find to minimize the total demand weighted cost between the demand and the new facility location (minisum objective function). All of the methods have been applied successfully. The results obtained have been analyze and compared by the total distances.

2025, Zaenal Arifin

Tugas Kuliah

2025

Dalam konteks perencanaan wilayah, ruang atau spasial bukan hanya sebatas tempat, melainkan unsur penting yang mempengaruhi jalannya sistem perekonomian. Ruang memiliki potensi sebagai sumber keuntungan ekonomi dan geografis, baik melalui kemudahan aksesibilitas, ketersediaan bahan baku, maupun efisiensi biaya produksi dan transaksi. Karena itulah, muncul kebutuhan untuk melihat fenomena ekonomi tidak hanya secara statis, tetapi juga secara dinamis dan evolusioner. Pendekatan ini menempatkan ruang sebagai bagian penting dari proses pembangunan. Teori lokasi dan teori perilaku merupakan dua kerangka pemikiran utama dalam memahami distribusi aktivitas ekonomi dalam ruang dan bagaimana manusia mengambil keputusan atas lokasi tersebut. Teori lokasi merupakan cabang tertua dari ekonomi regional yang berusaha menjelaskan penyebaran aktivitas ekonomi berdasarkan prinsip-prinsip ekonomi mikro. Pemikiran awal mengenai teori ini dapat ditelusuri dari karya Johann Heinrich von Thünen pada tahun 1826. Dalam modelnya, Thünen menjelaskan bahwa akses ke pasar mempengaruhi jenis aktivitas pertanian berdasarkan biaya transportasi dan nilai sewa lahan. Ide ini menjadi dasar pemikiran bahwa lokasi kegiatan ekonomi sangat ditentukan oleh jarak dan efisiensi biaya. Lebih dari lima puluh tahun setelahnya, Carl Launhardt mengembangkan pendekatan terhadap lokasi industri dan wilayah pasar. Gagasan ini kemudian disempurnakan oleh Alfred Weber pada tahun 1929 melalui teori lokasi industri. Weber memperhitungkan faktor biaya transportasi, biaya tenaga kerja, dan keuntungan aglomerasi sebagai pertimbangan dalam menentukan lokasi optimal industri. Di sisi lain, Alfred Marshall, melalui karyanya Principles of Economics, menekankan pentingnya konsentrasi industri sejenis dalam satu wilayah, yang menghasilkan manfaat berupa efisiensi tenaga kerja, pemasok, dan pertukaran informasi antar pelaku usaha. Selain tokoh-tokoh tersebut, pemikiran mengenai lokasi juga diperluas oleh banyak ekonom dan ahli geografi lainnya yang berusaha menjelaskan pola spasial berdasarkan fungsi dan interaksi antar wilayah. Walter Christaller memperkenalkan Central Place Theory pada tahun 1933 yang menjelaskan pola lokasi permukiman dan pusat pelayanan dalam bentuk hierarki. Christaller beranggapan bahwa suatu kota pusat akan dikelilingi oleh kota-kota kecil yang berfungsi menerima dan mendistribusikan barang dan jasa. Teori ini sangat berpengaruh dalam menentukan lokasi layanan dan fasilitas umum. Sementara itu, August Lösch mengembangkan teori maksimalisasi keuntungan, menyatakan bahwa lokasi ideal bagi industri adalah lokasi yang mampu memberikan laba terbesar, bukan hanya lokasi dengan biaya produksi paling rendah seperti dalam pandangan Weber. Pemikiran serupa juga dikembangkan oleh Homer Hoyt melalui Sector Model yang menjelaskan pertumbuhan kota berdasarkan sektor-sektor pendapatan dan jalur transportasi utama. Edgar Hoover memberikan pendekatan berdasarkan harga pengiriman dan

2025, TEORI LOKASI DAN TEORI BEHAVIOUR

Ruang atau lokasi memiliki pengaruh besar terhadap sistem ekonomi karena kedekatan antara berbagai aktivitas ekonomi dapat meningkatkan efisiensi produksi, mengurangi biaya, dan memberikan keuntungan seperti akses yang lebih mudah ke pasar dan bahan baku. Oleh karena itu, penting untuk menganalisis ekonomi secara dinamis, bukan hanya melihatnya dari sudut pandang yang tetap. Ekonomi regional adalah studi tentang bagaimana pasar berfungsi di berbagai wilayah yang berbeda. Ada dua cabang utama dalam ekonomi regional:
Teori Lokasi: Ini membahas bagaimana dan mengapa kegiatan ekonomi memilih tempat tertentu untuk beroperasi. Misalnya, perusahaan mungkin memilih lokasi yang dekat dengan pelanggan atau sumber bahan baku untuk menghemat biaya.Teori Pertumbuhan Regional: Ini fokus pada bagaimana pertumbuhan ekonomi terjadi di berbagai wilayah dan bagaimana pendapatan didistribusikan di antara mereka.
Teori lokasi sangat penting dalam ekonomi regional karena membantu menjelaskan mengapa ada ketimpangan dalam distribusi aktivitas ekonomi. Misalnya, beberapa daerah mungkin memiliki lebih banyak perusahaan atau lapangan kerja dibandingkan yang lain. Ini bisa disebabkan oleh faktor-faktor seperti aglomerasi, di mana perusahaan-perusahaan berkumpul di satu tempat untuk saling mendukung, dan eksternalitas, yang merupakan efek samping dari aktivitas ekonomi yang dapat mempengaruhi daerah sekitarnya.

2025, Muchammad Muzaqi

Teori lokasi dan teori perilaku telah menjadi fondasi penting dalam studi geografi ekonomi dan perencanaan wilayah. Pemikiran klasik dari tokoh-tokoh seperti von Thünen, Christaller, Weber, hingga pendekatan perilaku oleh Pred, memberikan kerangka analitis untuk memahami bagaimana ruang dimanfaatkan secara ekonomi dan sosial. Seiring dengan berkembangnya konteks globalisasi, urbanisasi, serta tantangan-tantangan kontemporer seperti perubahan iklim dan transformasi digital, teori-teori ini mendapatkan relevansi baru. Esai ini mengkaji kembali bagaimana teori lokasi dan teori perilaku dapat diadaptasi untuk menjawab tantangan pembangunan wilayah yang inklusif, efisien, dan berkelanjutan dalam kerangka interdisipliner yang menggabungkan dimensi spasial, sosial, dan ekonomi

2025, Puri Retno Nurlita

Perencanaan wilayah merupakan upaya strategis dalam mengatur pemanfaatan ruang guna mencapai pembangunan yang berkelanjutan dan berkeadilan. Dalam proses ini, dua pendekatan teoritis yang sangat penting adalah teori lokasi dan teori behaviour. Teori lokasi fokus pada bagaimana dan mengapa aktivitas ekonomi serta sosial tersebar dalam ruang geografis tertentu, sedangkan teori behaviour menekankan pada aspek perilaku dan keputusan subjektif individu dalam menanggapi ruang. Keputusan mengenai pemilihan lokasi suatu aktivitas tidak hanya ditentukan oleh efisiensi biaya atau jarak fisik, tetapi juga oleh preferensi, persepsi, serta keterbatasan informasi yang dimiliki pelaku. Oleh karena itu, memahami kedua teori ini secara bersamaan sangatlah penting untuk merancang tata ruang yang adaptif, efisien, dan responsif terhadap kebutuhan masyarakat. Esai ini bertujuan untuk menguraikan pemikiran utama dari teori lokasi dan teori behaviour, serta meninjau perannya dalam perencanaan wilayah.

2025

HidroSIG is a tool for hydrological variables visualization and analysis, using a set of modules that make this software a powerful tool for hydrological modeling. HidroSIG has tools for digital terrain models processing, water supply estimation using long term water balance in watersheds, a rainfall-runoff model, a model for landslide susceptibility estimation, an one-dimensional pollutant transport model, tools for homogeneity analysis in time series and tools for satellite images classification. The tools in development status are also described.

2025

The possibility of generating of electromagnetic radiation at harmonics of the pump wave in the ionospheric plasma is still open because of complexity of the experiments on its detection. The fact is that the parasitic generation of harmonics can occur in the output circuit of the transmitter, and to separate it from the possible ionospheric effects is very difficult. To solve the problem of detecting the 2 nd harmonic which is excited in the ionosphere, the special scheme of the experiment was proposed that is based on using the stable low-power probe wave on the frequency near the second harmonic of the pump wave for inspecting the propagation conditions of parasitic radiation. The conclusion about the ionospheric generation of the 2 nd harmonic was done by comparing its parameters with those of the probe signal.

2025, PLOS ONE

Blood transportation is a critical aspect of the healthcare systems, ensuring whole blood and blood products are delivered to patients in a timely and efficient manner. However, transportation of blood and other medical supplies can be challenging, especially in urban areas with limited infrastructure and heavy traffic. Drones have become increasingly important in recent years as a means of delivering medical supplies, including blood, due to their ability to provide fast, reliable, and cost-effective transportation. This study proposes two mathematical programming models in the hierarchical structure to improve decision-making for strategic and operational planning in the blood supply chain network. The limited information available in strategic planning presents risks to the blood supply chain, making it imperative to address uncertainties. To tackle this challenge, a novel approach called Scenario-based Robust Bi-objective Optimization has been proposed. The first model employs this approach to efficiently handle demand uncertainty by simultaneously maximizing the covered demand and minimizing costs. The model is subsequently solved using the augmented ε-constraint method. The second model is a routing-scheduling operational model that aims to minimize the sum of operations time, taking into account time windows for blood collection centers and hospitals. The developed hierarchical model is implemented in a three-level supply chain of Tehran province under three crisis scenarios in different parts. The findings and analysis of this implementation suggest that it is beneficial to set up drone stations in costeffective and central locations to avoid costly network design. Furthermore, utilizing the minimum number of feasible drones enhances operational time and results in cost savings and increased efficiency. Overall, this study highlights the potential of using drones for blood transportation in urban settings, which can have significant implications for improving the quality of healthcare delivery.

2025, Fire Technology

Tower-mounted camera-based wildfire detection systems provide an effective means of early forest fire detection. Historically, tower sites have been identified by foresters and locals with intimate knowledge of the terrain and without the aid of computational optimisation tools. When moving into vast new territories and without the aid of local knowledge, this process becomes cumbersome and daunting. In such instances, the optimisation of final site layouts may be streamlined if a suitable strategy is employed to limit the candidate sites to landforms which offer superior system visibility. A framework for the exploitation of landforms for these purposes is proposed. The landform classifications at 165 existing tower sites from wildfire detection systems in South Africa, Canada and the USA are analysed using the geomorphon technique, and it is noted that towers are located at or near certain landform types. A metaheuristic and integer linear programming approach is then employed to ...

2025, International Journal of Wildland Fire

Early forest fire detection can effectively be achieved by systems of specialised tower-mounted cameras. With the aim of maximising system visibility of smoke above a prescribed region, the process of selecting multiple tower sites from a large number of potential site locations is a complex combinatorial optimisation problem. Historically, these systems have been planned by foresters and locals with intimate knowledge of the terrain rather than by computational optimisation tools. When entering vast new territories, however, such knowledge and expertise may not be available to system planners. A tower site-selection optimisation framework that may be used in such circumstances is described in this paper. Metaheuristics are used to determine candidate site layouts for an area in the Nelspruit region in South Africa currently monitored by the ForestWatch detection system. Visibility cover superior to that of the existing system in the region is achieved and obtained in several days, ...

2025

The design of vehicle routes on the way to distribute important items to determine the location of the facility aims to minimize the total mileage of the vehicle so as to minimize distribution costs. This means choosing a sub collection of facilities and planning delivery routes that can meet customer demand. In this case, limits are given to the routes that must be passed for shipping.

2025

The design of vehicle routes on the way to distribute important items to determine the location of the facility aims to minimize the total mileage of the vehicle so as to minimize distribution costs. This means choosing a sub collectionof facilities and planning delivery routes that can meet customer demand. In this case, limits are given to the routes that must be passed for shipping.

2025

Urbanization is the most important aspect of societal advancement, particularly in densely populated capitals like the city of Dhaka in Bangladesh. There have been numerous mega projects incorporated within the city, but there is still a lack of proper planning mechanisms for further expansion. As the city continues to evolve, efficient planning becomes imperative to sustain growth and enhance living standards. With the help of Voronoi diagrams, this research offers a systemic approach to expanding Dhaka's urban landscape, which, to our knowledge, is a unique approach to solving the problem of representing Dhaka city. Through a fusion of Voronoi tessellation and Delaunay triangulation, the key map zones of the city are mapped, identifying optimal expansion sites and the shortest destination points for future infrastructure project routes. By addressing Sustainable Development Goal 11 (Sustainable Cities and Communities), the methodology aims to foster sustainable urban growth, enhance livelihoods, and mitigate congestion. Through empirical analysis and spatial modeling, the findings in the research provide actionable insights for policymakers, urban planners, and stakeholders, facilitating informed decision-making for Dhaka's sustainable development trajectory.

2025, Naval Research Logistics

We consider a class of facility location problems with a time dimension, which requires assigning every customer to a supply facility in each of a finite number of periods. Each facility must meet all assigned customer demand in every period at a minimum cost via its production and inventory decisions. We provide exact branch-and-price algorithms for this class of problems and several important variants. The corresponding pricing problem takes the form of an interesting class of production planning and order selection problems. This problem class requires selecting a set of orders that maximizes profit, defined as the revenue from selected orders minus production-planning-related costs incurred in fulfilling the selected orders. We provide polynomial-time dynamic programming algorithms for this class of pricing problems, as well as for generalizations thereof. Computational testing indicates the advantage of our branch-and-price algorithm over various approaches that use commercial software packages. These tests also highlight the significant cost savings possible from integrating location with production and inventory decisions and demonstrate that the problem is rather insensitive to forecast errors associated with the demand streams.

2025, Naval Research Logistics (NRL)

2025, Computers & Operations Research

Hub location problems are widely studied in the area of location theory, where they involve locating the hub facilities and designing the hub networks. In this paper, we present a new and robust solution based on a genetic search framework for the uncapacitated single allocation hub location problem (USAHLP). To present its e ectiveness, we compare the solutions of our GA-based method with the best solutions presented in the literature by considering various problem sizes of the CAB data set and the AP data set. The experimental work demonstrates that even for larger problems the results of our method signiÿcantly surpass those of the related work with respect to both solution quality and the CPU time to obtain a solution. Speciÿcally, the results from our method match the optimal solutions found in the literature for all test cases generated from the CAB data set with signiÿcantly less running time than the related work. For the AP data set, our solutions match the best solutions of the reference study with an average of 8 times less running time than the reference study. Its performance, robustness and substantially low computational e ort justify the potential of our method for solving larger problem sizes.

2025

Las estructuras monumentales prehistóricas construidas mediante zanjas continuas excavadas en el suelo de la Amazonia brasileña, son yacimientos que comprenden varias formas geométricas de diversos tamaños. Actualmente se conocen 291 yacimientos arqueológicos, la mayor parte de los cuales han sido mapeados por medio de imágenes de satélite. Estas construcciones prehistóricas fueron localizadas mediante la combinación de una serie de estrategias de prospección que incluyen el uso de imágenes satélites, sobrevuelos y otras tecnologías que posibilitaron su identificación. En un análisis de caracterización cuantitativa y morfológica y a través da estadísticas, obtuvimos como principales resultados que existe una gran dispersión de los datos correspondientes a su tamaño, siendo menor la variación para la profundidad, el valor medio de las áreas de los recintos con zanjas perimetrales es 17.490,6 m 2 , a pesar de que el 40,3% mide menos de una hectárea (10.000 m ), la altitud media a la que se encuentran es de 194,4 metros y ésta es la variable que mejor correlación tiene con la posición geográfica. Con la ayuda de gvSIG, Sextante, GRASS y R, hemos tratado de caracterizar la ubicación de los yacimientos atendiendo a diferentes variables entre las que destacan la altitud relativa, la orientación, la distancia al curso de agua más próximo, la pendiente y la posición relativa en el territorio. La intención es intentar predecir en qué áreas, hoy en día cubiertas por la masa forestal, se pueden encontrar estructuras semejantes a las localizadas en las áreas abiertas. Este carácter predictivo de nuestras observaciones sería de vital importancia para poder definir futuras prospecciones en las áreas boscosas de la Amazonia.

2025, European Journal of Operational Research

2025, RAIRO - Operations Research

2025, European Journal of Operational Research

The simple plant location problem deals with the selection of facility sites from a set of possible locations with the intention of serving a given set of customers from the chosen locations. The objective is to minimize the sum of the fixed charges for establishing the facilities and the transportation costs corresponding to the supply of the demands. We show how to modify a primal-dual version of Erlenkotter's exact algorithm to get an improved procedure. Computational experience with large-scale problems indicates that, compared with Erlenkotter's code, an implementation of the modified algorithm is faster by more than one order of magnitude. For real-life problems with 1500 potential facility sites the increase of computational speed may even exceed the factor of 100.

2025, Springer eBooks

We apply and extend the priority algorithm framework introduced by Borodin, Nielsen and Racko to de ne \greedy-like" algorithms for (uncapacitated) facility location problems and set cover. These problems have been the focus of extensive research from the point of view of approximation algorithms, and for both problems, greedy-like algorithms have been proposed and analyzed. The priority algorithm de nitions are general enough so as to capture a broad class of algorithms that can be characterized as \greedy-like" while still possible to derive nontrivial lower bounds on the approximability of the problems by algorithms in such a class. Our results are orthogonal to complexity considerations, and hence apply to algorithms that are not necessarily polynomial-time. best known polynomial time computable approximation ratio (essentially ln n, where n is the number of elements in the underlying universe) for the (weighted) set cover problem is achieved by a most natural greedy algorithm 13] 15] 6] and quite good approximation ratios (namely, 1:61 12] and 1:861 16]) have been derived by greedy-like algorithms for the metric uncapacitated facility location problem. For these two optimization problems, we apply the priority-algorithm framework and derive lower bounds on the approximation ratio for algorithms in this class. Informally, priority algorithms are characterized by the following two properties: 1. The algorithm speci es an ordering of \the input items" and each input item is considered in this order. 2. As each input item is considered, the algorithm must make an \irrevocable decision" concerning the input input. To make these concepts precise, (i.e., what precisely an \input item" and an \irrevocable decision" are) one has to apply the framework to particular problems (see section 2.2). The goal is to make the de nitions su ciently general and robust so as to capture known algorithms and anything that would be classi ed as \greedy-like" while still being su ciently restrictive that interesting lower bounds can be derived. As in the competitive analysis of online algorithms, priority algorithm lower bounds are orthogonal to complexity bounded approximation ratios. That is, although greedy algorithms are highly desirable because they tend to be time e cient, the de nition of priority algorithms permits arbitrarily complex (in terms of computing time) computation while deriving lower bounds by exploiting the structure of the algorithm. Depending on whether the ordering changes throughout the execution of the algorithm, two classes of priority algorithms can be de ned: Algorithms in the class Fixed Priority decide the ordering before any input item is considered and this ordering does not change throughout the execution of the algorithm. Algorithms in the more general class Adaptive Priority are allowed to specify a new ordering after each input item is processed. The new ordering can thus depend on input items already considered. As argued in 5], a further distinction can be made for Adaptive Priority algorithms, depending on the information the algorithm maintains on input items considered in the past. At one extreme, the irrevocable decision in a memoryless Adaptive Priority algorithm depends only on the \current con guration"; (e.g., for the facility location problem, only on facilities already considered and opened in the solution being constructed). At the other extreme, the algorithm can keep track of all input items considered in the past, and the corresponding decisions (e.g., in facility location, the algorithm knows whether a facility is has already considered has been opened). As in 5], \greedy algorithms" are ( xed or adaptive) priority algorithms, which satisfy an additional property: the irrevocable decision is such that the objective function is locally optimized. More speci cally, the objective function must be optimized as if the the input currently being considered is the last input. The de nition suggests that it is the nature of the decision and not the ordering that determines \greediness". Within this framework, we prove the following lower bounds: 1. The set cover problem over a universe of n elements.

2025, Proceedings of the 31st conference on Winter simulation Simulation---a bridge to the future - WSC '99

The Linear Move and Exchange Move Optimization (LEO) is an algorithm based on a simulated annealing algorithm (SA), a relatively recent algorithm for solving hard combinatorial optimization problems. The LEO algorithm was successfully applied to a facility layout problem, a scheduling problem and a line balancing problem. In this paper we will try to apply the LEO algorithm to the problem of optimizing a manufacturing simulation model, based on a Steelworks Plant. This paper also demonstrates the effectiveness and versatility of this algorithm. We compare the search effort of this algorithm with a Genetic Algorithm (GA) implementation of the same problem.

2025, Conflict and Health

Objectives: Using Geographical Information System (GIS) as a tool to determine access to and gaps in providing HIV counselling and testing (VCT), treatment (ART) and mother-to-child transmission (PMTCT) services in conflict affected northern Uganda. Methods: Cross-sectional data on availability and utilization, and geo-coordinates of health facilities providing VCT, PMTCT, and ART were collected in order to determine access. ArcView software produced maps showing locations of facilities and Internally Displaced Population(IDP) camps. Findings: There were 167 health facilities located inside and outside 132 IDP camps with VCT, PMTCT and ART services provided in 32 (19.2%), 15 (9%) and 10 (6%) facilities respectively. There was uneven availability and utilization of services and resources among districts, camps and health facilities. Inadequate staff and stock-out of essential commodities were found in lower health facility levels. Provision of VCT was 100% of the HSSP II target at health centres IV and hospitals but 28% at HC III. For PMTCT and ART, only 42.9% and 20% of the respective targets were reached at the health centres IV. Access to VCT, PMTCT and ART services was geographically limited due to inadequacy and heterogeneous dispersion of these services among districts and camps. GIS mapping can be effective in identifying service delivery gaps and presenting complex data into simplistic results hence can be recommended in need assessments in conflict settings.

2025, European Journal of Operational Research

An undesirable facility is to be located within some feasible region of any shape in the plane or on a planar network. Population is supposed to be concentrated at a ®nite number n of points. Two criteria are taken into account: a radius of in¯uence to be maximised, indicating within which distance from the facility population disturbance is taken into consideration, and the total covered population, i.e. lying within the in¯uence radius from the facility, which should be minimised. Low complexity polynomial algorithms are derived to determine all nondominated solutions, of which there are only On 3 for a ®xed feasible region or On 2 when locating on a planar network. Once obtained, this information allows almost instant answers and a trade-o sensitivity analysis to questions such as minimising the population within a given radius (minimal covering problem) or ®nding the largest circle not covering more than a given total population.

2025, OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information)

This paper presents a global approach to the validation of the parameters that enter into the neutronics simulation tools for advanced fast reactors with the objective to reduce the uncertainties associated to crucial design parameters. This global approach makes use of sensitivity/uncertainty methods; statistical data adjustments; integral experiment selection, analysis and "representativity" quantification with respect to a reference system; scientifically based cross section covariance data and appropriate methods for their use in multigroup calculations. This global approach has been applied to the uncertainty reduction on the criticality of the Advanced Burner Reactor, (both metal and oxide core versions) presently investigated in the frame of the GNEP initiative. The results obtained are very encouraging and allow to indicate some possible improvements of the ENDF/B-VII data file.

2025, … -AMERICAN NUCLEAR SOCIETY

This is a preprint of a paper intended for publication in a journal or proceedings. Since changes may be made before publication, this preprint should not be cited or reproduced without permission of the author. This document was prepared... more

2025

We consider a single-part, two-echelon supply chain problem for spare parts. The network consists of a single manufacturing plant, a set of service centers (SCs) and a set of customers. Both echelons keep spare parts using the base-stock replenishment policy. The plant behaves as an M/M/1 queueing system and has limited production and storage capacity. Demand faced by each SC follows an independent Poisson process. The problem is to determine optimal location-allocation and optimal base-stock levels at both echelons while satisfying the target service levels and customer preferences of SCs. We develop a mixed integer non-linear programming model and use cutting-plane method to optimize the inventory-location decisions. We present an exact solution procedure for the inventory stocking problem and demonstrate the limitations of using traditional inventory models like METRIC-like and Approximate in case of high utilization rates. We show the effectiveness of our proposed cutting-plane ...

2025

In the realm of service parts management, customer relationships are often established through service agreements that extend over a period of months or years. These agreements typically apply to a product (or group of products) that the customer has purchased, and specify the type of service that will be provided, as well as the timing with which the service will take place. In the case of a customer that operates in multiple locations, service agreements may apply to several products across several locations. In this paper we describe a continuous review inventory model for a multi-item, multi-echelon distribution system for service parts in which service level constraints exist for general groups of items across multiple locations and distribution channels. In addition to instantaneous service level constraints, a special class of time-based service level constraints are also considered, in which the specified service times coincide with transport times from replenishment sites within the distribution network. We derive exact fill rate expressions for each item's distribution channel and describe a solution approach for determining target inventory levels that meet all service level constraints at minimum investment.

2025

PLANEX is a system that solves the road network construction together with the location of harvesting machinery, skidders and towers, in planning the habilitation of up to a thousand hectares of terrain to harvest. The system is fed from digitalized information stored in geographic databases. This graphic tool automatically designs the road network, which is the third most important operational

2025

The modern supply chain management is witnessing a radical transformation as an effect of competitive strategy. The domain or reverse logistics has been now an area of research for practitioners as well as academicians. The functional part of machines as well as subassemblies often faces the situation of return. We conducted a survey on return of parts and subassemblies to investigate the factors governing their reverse logistics in terms of cost effectiveness and service of reverse logistics. This study has revealed that organizational role, returns policies, forecasting and retrieval centres have a positive impact of handling of returns in the form of parts and subassemblies. The result of this study provides a template guideline for designing a cost effective reverse logistics program with an improved customer service.

2025

In this study, we review the existing literature on network location problems. The study has a broad scope that includes problems featuring desirable and undesirable facilities, point facilities and extensive facilities, monopolistic and competitive markets, and single or multiple objectives. Deterministic and stochastic models as well as robust models are covered. Demand data aggregation is also discussed. More than 500 papers in this area are reviewed and critical issues, research directions, and problem extensions are emphasized.

2025, Oles Honchar Dnipro National University

This research article explores some new properties of generalized hypergeometric function and its q-analogue. The connections between 2R1upsilon(z){}_2R_1^{\upsilon} (z)2R1upsilon(z), the Wright function, and generalized Mittag-Leffler functions are explored. The authors introduce the q-analogue of generalized hypergeometric function denoted by 2R1 υ,q (z) and discuss its properties and connections with q-Wright function and q-versions of generalized Mittag-Leffler functions. We get the q-integral transforms such as q-Mellin, q-Euler (beta), q-Laplace, q-sumudu, and q-natural transforms of Wright-type generalized q-hypergeometric function. This article contributes to the understanding of hypergeometric functions in q-calculus.