Next Issue
Volume 16, August
Previous Issue
Volume 16, June
 
 

Algorithms, Volume 16, Issue 7 (July 2023) – 47 articles

Cover Story (view full-size image): There is a growing interest in automatically tuning the hyperparameters of deep learning models to reduce complexity and significant advancements have been made to this effect that promise improved performance with fewer resources. This study proposes HyperGE, a two-stage grammar-guided search space pruning algorithm for automatically tuning hyperparameters of deep learning models. HyperGE is driven by grammatical evolution (GE), a bioinspired population-based machine learning algorithm. In Stage 1 of HyperGE, the hyperparameter search space is explored globally by individuals. In Stage 2, the intuitions from the preceding stage significantly reduce the search space by a factor of ~90% and guide the exploitation within this refined space leading to optimal configurations with fewer trials. View this paper
  • Issues are regarded as officially published after their release is announced to the table of contents alert mailing list.
  • You may sign up for e-mail alerts to receive table of contents of newly released issues.
  • PDF is the official format for papers published in both, html and pdf forms. To view the papers in pdf format, click on the "PDF Full-text" link, and use the free Adobe Reader to open them.
Order results
Result details
Section
Select all
Export citation of selected articles as:
14 pages, 670 KiB  
Article
Design of Cloud-Based Real-Time Eye-Tracking Monitoring and Storage System
by Mustafa Can Gursesli, Mehmet Emin Selek, Mustafa Oktay Samur, Mirko Duradoni, Kyoungju Park, Andrea Guazzini and Antonio Lanatà
Algorithms 2023, 16(7), 355; https://doi.org/10.3390/a16070355 - 24 Jul 2023
Cited by 4 | Viewed by 1747
Abstract
The rapid development of technology has led to the implementation of data-driven systems whose performance heavily relies on the amount and type of data. In the latest decades, in the field of bioengineering data management, among others, eye-tracking data have become one of [...] Read more.
The rapid development of technology has led to the implementation of data-driven systems whose performance heavily relies on the amount and type of data. In the latest decades, in the field of bioengineering data management, among others, eye-tracking data have become one of the most interesting and essential components for many medical, psychological, and engineering research applications. However, despite the large usage of eye-tracking data in many studies and applications, a strong gap is still present in the literature regarding real-time data collection and management, which leads to strong constraints for the reliability and accuracy of on-time results. To address this gap, this study aims to introduce a system that enables the collection, processing, real-time streaming, and storage of eye-tracking data. The system was developed using the Java programming language, WebSocket protocol, and Representational State Transfer (REST), improving the efficiency in transferring and managing eye-tracking data. The results were computed in two test conditions, i.e., local and online scenarios, within a time window of 100 seconds. The experiments conducted for this study were carried out by comparing the time delay between two different scenarios, even if preliminary results showed a significantly improved performance of data management systems in managing real-time data transfer. Overall, this system can significantly benefit the research community by providing real-time data transfer and storing the data, enabling more extensive studies using eye-tracking data. Full article
(This article belongs to the Special Issue 2022 and 2023 Selected Papers from Algorithms Editorial Board Members)
Show Figures

Figure 1

20 pages, 1201 KiB  
Article
Hierarchical Reinforcement Learning for Crude Oil Supply Chain Scheduling
by Nan Ma, Ziyi Wang, Zeyu Ba, Xinran Li, Ning Yang, Xinyi Yang and Haifeng Zhang
Algorithms 2023, 16(7), 354; https://doi.org/10.3390/a16070354 - 24 Jul 2023
Cited by 1 | Viewed by 1501
Abstract
Crude oil resource scheduling is one of the critical issues upstream in the crude oil industry chain. It aims to reduce transportation and inventory costs and avoid alerts of inventory limit violations by formulating reasonable crude oil transportation and inventory strategies. Two main [...] Read more.
Crude oil resource scheduling is one of the critical issues upstream in the crude oil industry chain. It aims to reduce transportation and inventory costs and avoid alerts of inventory limit violations by formulating reasonable crude oil transportation and inventory strategies. Two main difficulties coexist in this problem: the large problem scale and uncertain supply and demand. Traditional operations research (OR) methods, which rely on forecasting supply and demand, face significant challenges when applied to the complicated and uncertain short-term operational process of the crude oil supply chain. To address these challenges, this paper presents a novel hierarchical optimization framework and proposes a well-designed hierarchical reinforcement learning (HRL) algorithm. Specifically, reinforcement learning (RL), as an upper-level agent, is used to select the operational operators combined by various sub-goals and solving orders, while the lower-level agent finds a viable solution and provides penalty feedback to the upper-level agent based on the chosen operator. Additionally, we deploy a simulator based on real-world data and execute comprehensive experiments. Regarding the alert number, maximum alert penalty, and overall transportation cost, our HRL method outperforms existing OR and two RL algorithms in the majority of time steps. Full article
(This article belongs to the Section Algorithms for Multidisciplinary Applications)
Show Figures

Figure 1

22 pages, 640 KiB  
Article
Intelligent Identification of Trend Components in Singular Spectrum Analysis
by Nina Golyandina, Pavel Dudnik and Alex Shlemov
Algorithms 2023, 16(7), 353; https://doi.org/10.3390/a16070353 - 24 Jul 2023
Cited by 1 | Viewed by 1463
Abstract
Singular spectrum analysis (SSA) is a non-parametric adaptive technique used for time series analysis. It allows solving various problems related to time series without the need to define a model. In this study, we focus on the problem of trend extraction. To extract [...] Read more.
Singular spectrum analysis (SSA) is a non-parametric adaptive technique used for time series analysis. It allows solving various problems related to time series without the need to define a model. In this study, we focus on the problem of trend extraction. To extract trends using SSA, a grouping of elementary components is required. However, automating this process is challenging due to the nonparametric nature of SSA. Although there are some known approaches to automated grouping in SSA, they do not work well when the signal components are mixed. In this paper, a novel approach that combines automated identification of trend components with separability improvement is proposed. We also consider a new method called EOSSA for separability improvement, along with other known methods. The automated modifications are numerically compared and applied to real-life time series. The proposed approach demonstrated its advantage in extracting trends when dealing with mixed signal components. The separability-improving method EOSSA proved to be the most accurate when the signal rank is properly detected or slightly exceeded. The automated SSA was very successfully applied to US Unemployment data to separate an annual trend from seasonal effects. The proposed approach has shown its capability to automatically extract trends without the need to determine their parametric form. Full article
(This article belongs to the Special Issue Machine Learning for Time Series Analysis)
Show Figures

Figure 1

18 pages, 896 KiB  
Article
Generating Loop Patterns with a Genetic Algorithm and a Probabilistic Cellular Automata Rule
by Rolf Hoffmann
Algorithms 2023, 16(7), 352; https://doi.org/10.3390/a16070352 - 24 Jul 2023
Viewed by 1158
Abstract
The objective is to find a Cellular Automata (CA) rule that can generate “loop patterns”. A loop pattern is given by ones on a zero background showing loops. In order to find out how loop patterns can be locally defined, tentative loop patterns [...] Read more.
The objective is to find a Cellular Automata (CA) rule that can generate “loop patterns”. A loop pattern is given by ones on a zero background showing loops. In order to find out how loop patterns can be locally defined, tentative loop patterns are generated by a genetic algorithm in a preliminary stage. A set of local matching tiles is designed and checked whether they can produce the aimed loop patterns by the genetic algorithm. After having approved a certain set of tiles, a probabilistic CA rule is designed in a methodical way. Templates are derived from the tiles, which then are used in the CA rule for matching. In order to drive the evolution to the desired patterns, noise is injected if the templates do not match or other constraints are not fulfilled. Simulations illustrate that loops and connected loops can be evolved by the CA rule. Full article
(This article belongs to the Special Issue Algorithms for Natural Computing Models)
Show Figures

Figure 1

17 pages, 2589 KiB  
Article
Learning from Imbalanced Datasets: The Bike-Sharing Inventory Problem Using Sparse Information
by Giovanni Ceccarelli, Guido Cantelmo, Marialisa Nigro and Constantinos Antoniou
Algorithms 2023, 16(7), 351; https://doi.org/10.3390/a16070351 - 22 Jul 2023
Viewed by 1155
Abstract
In bike-sharing systems, the inventory level is defined as the daily number of bicycles required to optimally meet the demand. Estimating these values is a major challenge for bike-sharing operators, as biased inventory levels lead to a reduced quality of service at best [...] Read more.
In bike-sharing systems, the inventory level is defined as the daily number of bicycles required to optimally meet the demand. Estimating these values is a major challenge for bike-sharing operators, as biased inventory levels lead to a reduced quality of service at best and a loss of customers and system failure at worst. This paper focuses on using machine learning (ML) classifiers, most notably random forest and gradient tree boosting, for estimating the inventory level from available features including historical data. However, while similar approaches adopted in the context of bike sharing assume the data to be well-balanced, this assumption is not met in the case of the inventory problem. Indeed, as the demand for bike sharing is sparse, datasets become biased toward low demand values, and systematic errors emerge. Thus, we propose to include a new iterative resampling procedure in the classification problem to deal with imbalanced datasets. The proposed model, tested on the real-world data of the Citi Bike operator in New York, allows to (i) provide upper-bound and lower-bound values for the bike-sharing inventory problem, accurately predicting both predominant and rare demand values; (ii) capture the main features that characterize the different demand classes; and (iii) work in a day-to-day framework. Finally, successful bike-sharing systems grow rapidly, opening new stations every year. In addition to changes in the mobility demand, an additional problem is that we cannot use historical information to predict inventory levels for new stations. Therefore, we test the capability of our model to predict inventory levels when historical data is not available, with a specific focus on stations that were not available for training. Full article
(This article belongs to the Special Issue Algorithms for Smart Cities)
Show Figures

Figure 1

16 pages, 1181 KiB  
Article
A Zoning Search-Based Multimodal Multi-Objective Brain Storm Optimization Algorithm for Multimodal Multi-Objective Optimization
by Jiajia Fan, Wentao Huang, Qingchao Jiang and Qinqin Fan
Algorithms 2023, 16(7), 350; https://doi.org/10.3390/a16070350 - 21 Jul 2023
Viewed by 1151
Abstract
For multimodal multi-objective optimization problems (MMOPs), there are multiple equivalent Pareto optimal solutions in the decision space that are corresponding to the same objective value. Therefore, the main tasks of multimodal multi-objective optimization (MMO) are to find a high-quality PF approximation in the [...] Read more.
For multimodal multi-objective optimization problems (MMOPs), there are multiple equivalent Pareto optimal solutions in the decision space that are corresponding to the same objective value. Therefore, the main tasks of multimodal multi-objective optimization (MMO) are to find a high-quality PF approximation in the objective space and maintain the population diversity in the decision space. To achieve the above objectives, this article proposes a zoning search-based multimodal multi-objective brain storm optimization algorithm (ZS-MMBSO). At first, the search space segmentation method is employed to divide the search space into some sub-regions. Moreover, a novel individual generation strategy is incorporated into the multimodal multi-objective brain storm optimization algorithm, which can improve the search performance of the search engineering. The proposed algorithm is compared with five famous multimodal multi-objective evolutionary algorithms (MMOEAs) on IEEE CEC2019 MMOPs benchmark test suite. Experimental results indicate that the overall performance of the ZS-MMBSO is the best among all competitors. Full article
(This article belongs to the Special Issue Nature-Inspired Algorithms for Optimization)
Show Figures

Figure 1

17 pages, 599 KiB  
Article
Two Medoid-Based Algorithms for Clustering Sets
by Libero Nigro and Pasi Fränti
Algorithms 2023, 16(7), 349; https://doi.org/10.3390/a16070349 - 20 Jul 2023
Cited by 1 | Viewed by 1184
Abstract
This paper proposes two algorithms for clustering data, which are variable-sized sets of elementary items. An example of such data occurs in the analysis of a medical diagnosis, where the goal is to detect human subjects who share common diseases to possibly predict [...] Read more.
This paper proposes two algorithms for clustering data, which are variable-sized sets of elementary items. An example of such data occurs in the analysis of a medical diagnosis, where the goal is to detect human subjects who share common diseases to possibly predict future illnesses from previous medical history. The first proposed algorithm is based on K-medoids and the second algorithm extends the random swap algorithm, which has proven to be capable of efficient and careful clustering; both algorithms depend on a distance function among data objects (sets), which can use application-sensitive weights or priorities. The proposed distance function makes it possible to exploit several seeding methods that can improve clustering accuracy. A key factor in the two algorithms is their parallel implementation in Java, based on functional programming using streams and lambda expressions. The use of parallelism smooths out the O(N2) computational cost behind K-medoids and clustering indexes such as the Silhouette index and allows for the handling of non-trivial datasets. This paper applies the algorithms to several benchmark case studies of sets and demonstrates how accurate and time-efficient clustering solutions can be achieved. Full article
(This article belongs to the Special Issue Supervised and Unsupervised Classification Algorithms (2nd Edition))
Show Figures

Figure 1

20 pages, 3735 KiB  
Article
Integrated Decision Support Framework of Optimal Scaffolding System for Construction Projects
by Haifeng Jin and Paul M. Goodrum
Algorithms 2023, 16(7), 348; https://doi.org/10.3390/a16070348 - 20 Jul 2023
Cited by 1 | Viewed by 1331
Abstract
Selecting the appropriate temporary facilities is important for reducing cost and improving the productivity and safety of craft professionals in construction projects. However, the manual planning process for scaffolding systems is typically prone to inefficiencies. This paper aims to develop a knowledge-based framework [...] Read more.
Selecting the appropriate temporary facilities is important for reducing cost and improving the productivity and safety of craft professionals in construction projects. However, the manual planning process for scaffolding systems is typically prone to inefficiencies. This paper aims to develop a knowledge-based framework for a scaffolding decision support system for industry. An integrated two-phase system was established, including a technical evaluation module and a knowledge-based module. First, the system identifies feasible scaffolding alternatives from the database through a rule-based algorithm. Second, a knowledge-based module was designed to assess the alternative performance. The framework effectively generated the ranking of scaffolding alternatives, and the top three influential factors were identified, including the site accessibility, protection to workers and health risk. Thus, an application study of an industrial steel project was proffered to validate the effectiveness of the framework. The proposed framework may help decision-making regarding the implementation of temporary facility planning in industry practices. It has wider applicability because it simultaneously considers site conditions, productivity, safety, and financial benefits, and is designed and implemented through a computerized path. The paper contributes to the industry by developing an integrated decision support system for temporary facilities. Additionally, the practical contribution of this research is the provision of an optimized scaffolding planning method that could be utilized as a guide when implementing the decision support system. Full article
(This article belongs to the Special Issue Simulation Modeling and Optimization Algorithms in Construction)
Show Figures

Figure 1

19 pages, 2972 KiB  
Article
Similarity Measurement and Classification of Temporal Data Based on Double Mean Representation
by Zhenwen He, Chi Zhang and Yunhui Cheng
Algorithms 2023, 16(7), 347; https://doi.org/10.3390/a16070347 - 19 Jul 2023
Viewed by 1245
Abstract
Time series data typically exhibit high dimensionality and complexity, necessitating the use of specific approximation methods to perform computations on the data. The currently employed compression methods suffer from varying degrees of feature loss, leading to potential distortions in similarity measurement results. Considering [...] Read more.
Time series data typically exhibit high dimensionality and complexity, necessitating the use of specific approximation methods to perform computations on the data. The currently employed compression methods suffer from varying degrees of feature loss, leading to potential distortions in similarity measurement results. Considering the aforementioned challenges and concerns, this paper proposes a double mean representation method, SAX-DM (Symbolic Aggregate Approximation Based on Double Mean Representation), for time series data, along with a similarity measurement approach based on SAX-DM. Addressing the trade-off between compression ratio and accuracy in the improved SAX representation, SAX-DM utilizes the segment mean and the segment trend distance to represent corresponding segments of time series data. This method reduces the dimensionality of the original sequences while preserving the original features and trend information of the time series data, resulting in a unified representation of time series segments. Experimental results demonstrate that, under the same compression ratio, SAX-DM combined with its similarity measurement method achieves higher expression accuracy, balanced compression rate, and accuracy, compared to SAX-TD and SAX-BD, in over 80% of the UCR Time Series dataset. This approach improves the efficiency and precision of similarity calculation. Full article
(This article belongs to the Special Issue Algorithms for Time Series Forecasting and Classification)
Show Figures

Figure 1

25 pages, 1920 KiB  
Article
A Physicist’s View on Partial 3D Shape Matching
by Patrice Koehl and Henri Orland
Algorithms 2023, 16(7), 346; https://doi.org/10.3390/a16070346 - 18 Jul 2023
Cited by 1 | Viewed by 1655
Abstract
A new algorithm is presented to compute nonrigid, possibly partial comparisons of shapes defined by unstructured triangulations of their surfaces. The algorithm takes as input a pair of surfaces with each surface given by a distinct and unrelated triangulation. Its goal is to [...] Read more.
A new algorithm is presented to compute nonrigid, possibly partial comparisons of shapes defined by unstructured triangulations of their surfaces. The algorithm takes as input a pair of surfaces with each surface given by a distinct and unrelated triangulation. Its goal is to define a possibly partial correspondence between the vertices of the two triangulations, with a cost associated with this correspondence that can serve as a measure of the similarity of the two shapes. To find this correspondence, the vertices in each triangulation are characterized by a signature vector of features. We tested both the LD-SIFT signatures, based on the concept of spin images, and the wave kernel signatures obtained by solving the Shrödinger equation on the triangulation. A cost matrix C is constructed such that C(k,l) is the norm of the difference of the signature vectors of vertices k and l. The correspondence between the triangulations is then computed as the transport plan that solves the optimal transport or optimal partial transport problem between their sets of vertices. We use a statistical physics approach to solve these problems. The presentation of the proposed algorithm is complemented with examples that illustrate its effectiveness and manageable computing cost. Full article
(This article belongs to the Collection Feature Papers in Algorithms for Multidisciplinary Applications)
Show Figures

Figure 1

20 pages, 1917 KiB  
Article
A Corrosion Maintenance Model Using Continuous State Partially Observable Markov Decision Process for Oil and Gas Pipelines
by Ezra Wari, Weihang Zhu and Gino Lim
Algorithms 2023, 16(7), 345; https://doi.org/10.3390/a16070345 - 18 Jul 2023
Viewed by 1113
Abstract
This paper proposes a continuous state partially observable Markov decision process (POMDP) model for the corrosion maintenance of oil and gas pipelines. The maintenance operations include complex and extensive activities to detect the corrosion type, determine its severity, predict the deterioration rate, and [...] Read more.
This paper proposes a continuous state partially observable Markov decision process (POMDP) model for the corrosion maintenance of oil and gas pipelines. The maintenance operations include complex and extensive activities to detect the corrosion type, determine its severity, predict the deterioration rate, and plan future inspection (monitoring) schemes and maintenance policy. A POMDP model is formulated as a decision-making support tool to effectively handle partially observed corrosion defect levels. It formulates states as the pipeline’s degradation level using a probability distribution. Inline inspection (ILI) methods estimate the latest state of the pipeline, which also defines the initial state of the optimization process. The set of actions comprises corrosion mitigation operations. The errors associated with the ILI method are used to construct the observation function for the model. The sum of inspection, maintenance operations, and failure costs for a given state and action are formulated as rewards. Numerical experiments are made based on data collected from the literature. The results showed that different policies, whether derived from solvers (theoretical) or determined from practical experience, can be compared to identify the best maintenance alternative using the model. It was also observed that the choice of the solvers is important since they affect the discounted rewards and the run time to obtain them. The model approximates the parameters and uncertainty associated with the propagation of corrosion, proficiency of inspection methods, and implementation of maintenance policies. Overall, it can be applied to improve the maintenance decision-making process for the oil and gas pipeline as it incorporates the stochastic features of the operation. Full article
(This article belongs to the Special Issue Simulation Modeling and Optimization Algorithms in Construction)
Show Figures

Figure 1

12 pages, 2900 KiB  
Article
Neural-Network-Based Quark–Gluon Plasma Trigger for the CBM Experiment at FAIR
by Artemiy Belousov, Ivan Kisel, Robin Lakos and Akhil Mithran
Algorithms 2023, 16(7), 344; https://doi.org/10.3390/a16070344 - 18 Jul 2023
Viewed by 1081
Abstract
Algorithms optimized for high-performance computing, which ensure both speed and accuracy, are crucial for real-time data analysis in heavy-ion physics experiments. The application of neural networks and other machine learning methodologies, which are fast and have high accuracy, in physics experiments has become [...] Read more.
Algorithms optimized for high-performance computing, which ensure both speed and accuracy, are crucial for real-time data analysis in heavy-ion physics experiments. The application of neural networks and other machine learning methodologies, which are fast and have high accuracy, in physics experiments has become increasingly popular over recent years. This paper introduces a fast neural network package named ANN4FLES developed in C++, which has been optimized for use on a high-performance computing cluster for the future Compressed Baryonic Matter (CBM) experiment at the Facility for Antiproton and Ion Research (FAIR, Darmstadt, Germany). The use of neural networks for classifying events during heavy-ion collisions in the CBM experiment is under investigation. This paper provides a detailed description of the application of ANN4FLES in identifying collisions where a quark–gluon plasma (QGP) was produced. The methodology detailed here will be used in the development of a QGP trigger for event selection within the First Level Event Selection (FLES) package for the CBM experiment. Fully-connected and convolutional neural networks have been created for the identification of events containing QGP, which are simulated with the Parton–Hadron–String Dynamics (PHSD) microscopic off-shell transport approach, for central Au + Au collisions at an energy of 31.2 A GeV. The results show that the convolutional neural network outperforms the fully-connected networks and achieves over 95% accuracy on the testing dataset. Full article
(This article belongs to the Special Issue 2022 and 2023 Selected Papers from Algorithms Editorial Board Members)
Show Figures

Figure 1

13 pages, 3521 KiB  
Article
Deep Learning for Detecting Verticillium Fungus in Olive Trees: Using YOLO in UAV Imagery
by Marios Mamalis, Evangelos Kalampokis, Ilias Kalfas and Konstantinos Tarabanis
Algorithms 2023, 16(7), 343; https://doi.org/10.3390/a16070343 - 17 Jul 2023
Cited by 7 | Viewed by 2133
Abstract
The verticillium fungus has become a widespread threat to olive fields around the world in recent years. The accurate and early detection of the disease at scale could support solving the problem. In this paper, we use the YOLO version 5 model to [...] Read more.
The verticillium fungus has become a widespread threat to olive fields around the world in recent years. The accurate and early detection of the disease at scale could support solving the problem. In this paper, we use the YOLO version 5 model to detect verticillium fungus in olive trees using aerial RGB imagery captured by unmanned aerial vehicles. The aim of our paper is to compare different architectures of the model and evaluate their performance on this task. The architectures are evaluated at two different input sizes each through the most widely used metrics for object detection and classification tasks (precision, recall, [email protected] and [email protected]:0.95). Our results show that the YOLOv5 algorithm is able to deliver good results in detecting olive trees and predicting their status, with the different architectures having different strengths and weaknesses. Full article
(This article belongs to the Collection Feature Papers in Algorithms for Multidisciplinary Applications)
Show Figures

Figure 1

16 pages, 1971 KiB  
Article
Leaking Gas Source Tracking for Multiple Chemical Parks within An Urban City
by Junwei Lang, Zhenjia Zeng, Tengfei Ma and Sailing He
Algorithms 2023, 16(7), 342; https://doi.org/10.3390/a16070342 - 17 Jul 2023
Cited by 1 | Viewed by 1210
Abstract
Sudden air pollution accidents (explosions, fires, leaks, etc.) in chemical industry parks may result in great harm to people’s lives, property, and the ecological environment. A gas tracking network can monitor hazardous gas diffusion using traceability technology combined with sensors distributed within the [...] Read more.
Sudden air pollution accidents (explosions, fires, leaks, etc.) in chemical industry parks may result in great harm to people’s lives, property, and the ecological environment. A gas tracking network can monitor hazardous gas diffusion using traceability technology combined with sensors distributed within the scope of a chemical industry park. Such systems can automatically locate the source of pollutants in a timely manner and notify relevant departments to take major hazards into their control. However, tracing the source of the leak in a large area is still a tough problem, especially within an urban area. In this paper, the diffusion of 79 potential leaking sources with consideration of different weather conditions and complex urban terrain is simulated by AERMOD. Only 61 sensors are used to monitor the gas concentration within such a large scale. A fully connected network trained with a hybrid strategy is proposed to trace the leaking source effectively and robustly. Our proposed model reaches a final classification accuracy of 99.14%. Full article
(This article belongs to the Special Issue Deep Neural Networks and Optimization Algorithms)
Show Figures

Figure 1

15 pages, 485 KiB  
Article
Minimizing Interference-to-Signal Ratios in Multi-Cell Telecommunication Networks
by Péter L. Erdős and Tamás Róbert Mezei
Algorithms 2023, 16(7), 341; https://doi.org/10.3390/a16070341 - 17 Jul 2023
Viewed by 890
Abstract
In contemporary wireless communication networks, base stations are organized into coordinated clusters (called cells) to jointly serve the users. However, such fixed systems are plagued by the so-called cell-edge problem: near the boundaries, the interference between neighboring clusters can result in very [...] Read more.
In contemporary wireless communication networks, base stations are organized into coordinated clusters (called cells) to jointly serve the users. However, such fixed systems are plagued by the so-called cell-edge problem: near the boundaries, the interference between neighboring clusters can result in very poor interference-to-signal power ratios. To achieve a high-quality service, it is an important objective to minimize the sum of these ratios over the cells. The most common approach to solving this minimization problem is arguably the spectral clustering method. In this paper, we propose a new clustering approach, which is deterministic and computationally much less demanding than current methods. Simulating on synthetic instances indicates that our methods typically provide higher quality solutions than earlier methods. Full article
Show Figures

Figure 1

18 pages, 612 KiB  
Article
A Blockchain-Based Auction Framework for Location-Aware Services
by Khaled Almiani, Mutaz Abu Alrub, Young Choon Lee, Taha H. Rashidi and Amirmohammad Pasdar
Algorithms 2023, 16(7), 340; https://doi.org/10.3390/a16070340 - 16 Jul 2023
Cited by 2 | Viewed by 1994
Abstract
As a critical factor in ensuring the growth of the electronic auction (e-auction) domain, the privacy and security of the participants (sellers and buyers) must always be guaranteed. Traditionally, auction data, including participant details, are stored in a third party (auctioneer) database. This [...] Read more.
As a critical factor in ensuring the growth of the electronic auction (e-auction) domain, the privacy and security of the participants (sellers and buyers) must always be guaranteed. Traditionally, auction data, including participant details, are stored in a third party (auctioneer) database. This leads to a high risk of a single point of failure in terms of privacy and security. Toward this end, blockchain technology has emerged as a promising decentralized communication paradigm to address such risks. This paper presents a blockchain-based auction framework as a decentralized e-auctioning framework for location-aware services. In particular, the framework consists of three components: pre-auctioning, main auctioning, and post-auctioning processes with four algorithms. Our primary focus is on location-aware services, such as storage space rental, apartment rental, transport hire, and parking space rental. The trading volumes are expected to be high; hence, simplifying the design is a crucial requirement. In addition to the benefits of eliminating the centralized entity (the auctioneer), fees are redistributed among participants as rewards. Further, we incorporate a service quality monitoring method that ranks the services provided by participants. This ranking allows participants to determine the rank of other participants with whom they wish to trade. We have conducted several experiments to evaluate the proposed framework’s cost feasibility and to ensure the ease of the business flow. Full article
(This article belongs to the Special Issue Advances in Distributed Algorithms)
Show Figures

Figure 1

28 pages, 8117 KiB  
Article
Chatbots for Cultural Venues: A Topic-Based Approach
by Vasilis Bouras, Dimitris Spiliotopoulos, Dionisis Margaris, Costas Vassilakis, Konstantinos Kotis, Angeliki Antoniou, George Lepouras, Manolis Wallace and Vassilis Poulopoulos
Algorithms 2023, 16(7), 339; https://doi.org/10.3390/a16070339 - 14 Jul 2023
Viewed by 2270
Abstract
Digital assistants—such as chatbots—facilitate the interaction between persons and machines and are increasingly used in web pages of enterprises and organizations. This paper presents a methodology for the creation of chatbots that offer access to museum information. The paper introduces an information model [...] Read more.
Digital assistants—such as chatbots—facilitate the interaction between persons and machines and are increasingly used in web pages of enterprises and organizations. This paper presents a methodology for the creation of chatbots that offer access to museum information. The paper introduces an information model that is offered through the chatbot, which subsequently maps the museum’s modeled information to structures of DialogFlow, Google’s chatbot engine. Means for automating the chatbot generation process are also presented. The evaluation of the methodology is illustrated through the application of a real case, wherein we developed a chatbot for the Archaeological Museum of Tripolis, Greece. Full article
(This article belongs to the Collection Feature Papers in Algorithms for Multidisciplinary Applications)
Show Figures

Figure 1

16 pages, 3049 KiB  
Article
A Largely Unsupervised Domain-Independent Qualitative Data Extraction Approach for Empirical Agent-Based Model Development
by Rajiv Paudel and Arika Ligmann-Zielinska
Algorithms 2023, 16(7), 338; https://doi.org/10.3390/a16070338 - 14 Jul 2023
Cited by 3 | Viewed by 1713
Abstract
Agent-based model (ABM) development needs information on system components and interactions. Qualitative narratives contain contextually rich system information beneficial for ABM conceptualization. Traditional qualitative data extraction is manual, complex, and time- and resource-consuming. Moreover, manual data extraction is often biased and may produce [...] Read more.
Agent-based model (ABM) development needs information on system components and interactions. Qualitative narratives contain contextually rich system information beneficial for ABM conceptualization. Traditional qualitative data extraction is manual, complex, and time- and resource-consuming. Moreover, manual data extraction is often biased and may produce questionable and unreliable models. A possible alternative is to employ automated approaches borrowed from Artificial Intelligence. This study presents a largely unsupervised qualitative data extraction framework for ABM development. Using semantic and syntactic Natural Language Processing tools, our methodology extracts information on system agents, their attributes, and actions and interactions. In addition to expediting information extraction for ABM, the largely unsupervised approach also minimizes biases arising from modelers’ preconceptions about target systems. We also introduce automatic and manual noise-reduction stages to make the framework usable on large semi-structured datasets. We demonstrate the approach by developing a conceptual ABM of household food security in rural Mali. The data for the model contain a large set of semi-structured qualitative field interviews. The data extraction is swift, predominantly automatic, and devoid of human manipulation. We contextualize the model manually using the extracted information. We also put the conceptual model to stakeholder evaluation for added credibility and validity. Full article
(This article belongs to the Special Issue Artificial Intelligence in Modeling and Simulation)
Show Figures

Figure 1

17 pages, 4293 KiB  
Article
A Hybrid Model for Analysis of Laser Beam Distortions Using Monte Carlo and Shack–Hartmann Techniques: Numerical Study and Experimental Results
by Ilya Galaktionov, Julia Sheldakova, Alexander Nikitin, Vladimir Toporovsky and Alexis Kudryashov
Algorithms 2023, 16(7), 337; https://doi.org/10.3390/a16070337 - 14 Jul 2023
Cited by 10 | Viewed by 1132
Abstract
The hybrid model for analyzing distortions of a laser beam passed through a moderately scattering medium with the number of scattering events up to 10 is developed and investigated. The model implemented the Monte Carlo technique to simulate the beam propagation through a [...] Read more.
The hybrid model for analyzing distortions of a laser beam passed through a moderately scattering medium with the number of scattering events up to 10 is developed and investigated. The model implemented the Monte Carlo technique to simulate the beam propagation through a scattering layer, a ray-tracing technique to propagate the scattered beam to the measurements plane, and the Shack–Hartmann technique to calculate the scattered laser beam distortions. The results obtained from the developed model were confirmed during the laboratory experiment. Both the numerical model and laboratory experiment showed that with an increase of the concentration value of scattering particles in the range from 105 to 106 mm−3, the amplitude of distortions of laser beam propagated through the layer of the scattering medium increases exponentially. Full article
(This article belongs to the Special Issue Algorithms and Calculations in Fiber Optics and Photonics)
Show Figures

Graphical abstract

21 pages, 6730 KiB  
Article
Simplified Routing Mechanism for Capsule Networks
by János Hollósi, Áron Ballagi and Claudiu Radu Pozna
Algorithms 2023, 16(7), 336; https://doi.org/10.3390/a16070336 - 13 Jul 2023
Cited by 2 | Viewed by 1505
Abstract
Classifying digital images using neural networks is one of the most fundamental tasks within the field of artificial intelligence. For a long time, convolutional neural networks have proven to be the most efficient solution for processing visual data, such as classification, detection, or [...] Read more.
Classifying digital images using neural networks is one of the most fundamental tasks within the field of artificial intelligence. For a long time, convolutional neural networks have proven to be the most efficient solution for processing visual data, such as classification, detection, or segmentation. The efficient operation of convolutional neural networks requires the use of data augmentation and a high number of feature maps to embed object transformations. Especially for large datasets, this approach is not very efficient. In 2017, Geoffrey Hinton and his research team introduced the theory of capsule networks. Capsule networks offer a solution to the problems of convolutional neural networks. In this approach, sufficient efficiency can be achieved without large-scale data augmentation. However, the training time for Hinton’s capsule network is much longer than for convolutional neural networks. We have examined the capsule networks and propose a modification in the routing mechanism to speed up the algorithm. This could reduce the training time of capsule networks by almost half in some cases. Moreover, our solution achieves performance improvements in the field of image classification. Full article
(This article belongs to the Special Issue Deep Learning Architecture and Applications)
Show Figures

Figure 1

22 pages, 1697 KiB  
Article
Basis Functions for a Transient Analysis of Linear Commensurate Fractional-Order Systems
by Dalibor Biolek, Viera Biolková, Zdeněk Kolka and Zdeněk Biolek
Algorithms 2023, 16(7), 335; https://doi.org/10.3390/a16070335 - 13 Jul 2023
Cited by 1 | Viewed by 1195
Abstract
In this paper, the possibilities of expressing the natural response of a linear commensurate fractional-order system (FOS) as a linear combination of basis functions are analyzed. For all possible types of sα-domain poles, the corresponding basis functions are found, the kernel [...] Read more.
In this paper, the possibilities of expressing the natural response of a linear commensurate fractional-order system (FOS) as a linear combination of basis functions are analyzed. For all possible types of sα-domain poles, the corresponding basis functions are found, the kernel of which is the two-parameter Mittag–Leffler function Eα,β, β = α. It is pointed out that there are mutually unambiguous correspondences between the basis functions of FOS and the known basis functions of the integer-order system (IOS) for α = 1. This correspondence can be used to algorithmically find analytical formulas for the impulse responses of FOS when the formulas for the characteristics of IOS are known. It is shown that all basis functions of FOS can be generated with Podlubny‘s function of type εk (t, c; α, α), where c and k are the corresponding pole and its multiplicity, respectively. Full article
(This article belongs to the Collection Feature Papers in Algorithms for Multidisciplinary Applications)
Show Figures

Figure 1

16 pages, 449 KiB  
Article
Optimal Maintenance Schedule for a Wind Power Turbine with Aging Components
by Quanjiang Yu, Ola Carlson and Serik Sagitov
Algorithms 2023, 16(7), 334; https://doi.org/10.3390/a16070334 - 13 Jul 2023
Cited by 2 | Viewed by 1546
Abstract
Wind power is one of the most important sources of renewable energy available today. A large part of the cost of wind energy is due to the cost of maintaining wind power equipment. When a wind turbine component fails to function, it might [...] Read more.
Wind power is one of the most important sources of renewable energy available today. A large part of the cost of wind energy is due to the cost of maintaining wind power equipment. When a wind turbine component fails to function, it might need to be replaced under circumstances that are less than ideal. This is known as corrective maintenance. To minimize unnecessary costs, a more active maintenance policy based on the life expectancy of the key components is preferred. Optimal scheduling of preventive maintenance activities requires advanced mathematical modeling. In this paper, an optimal preventive maintenance algorithm is designed using the renewal-reward theorem. In the multi-component setting, our approach involves a new idea of virtual maintenance that allows us to treat each replacement event as a renewal event even if some components are not replaced by new ones. The proposed optimization algorithm is applied to a four-component model of a wind turbine, and the optimal maintenance plans are computed for various initial conditions. The modeling results clearly show the benefit of PM planning compared to a pure CM strategy (about 30% lower maintenance cost). Full article
(This article belongs to the Special Issue Recent Advances in Nonsmooth Optimization and Analysis)
Show Figures

Figure 1

20 pages, 813 KiB  
Article
Three Metaheuristic Approaches for Tumor Phylogeny Inference: An Experimental Comparison
by Simone Ciccolella, Gianluca Della Vedova, Vladimir Filipović and Mauricio Soto Gomez
Algorithms 2023, 16(7), 333; https://doi.org/10.3390/a16070333 - 12 Jul 2023
Viewed by 1159
Abstract
Being able to infer the clonal evolution and progression of cancer makes it possible to devise targeted therapies to treat the disease. As discussed in several studies, understanding the history of accumulation and the evolution of mutations during cancer progression is of key [...] Read more.
Being able to infer the clonal evolution and progression of cancer makes it possible to devise targeted therapies to treat the disease. As discussed in several studies, understanding the history of accumulation and the evolution of mutations during cancer progression is of key importance when devising treatment strategies. Given the importance of the task, many methods for phylogeny reconstructions have been developed over the years, mostly employing probabilistic frameworks. Our goal was to explore different methods to take on this phylogeny inference problem; therefore, we devised and implemented three different metaheuristic approaches—Particle Swarm Optimization (PSO), Genetic Programming (GP) and Variable Neighbourhood Search (VNS)—under the Perfect Phylogeny and the Dollo-k evolutionary models. We adapted the algorithms to be applied to this specific context, specifically to a tree-based search space, and proposed six different experimental settings, in increasing order of difficulty, to test the novel methods amongst themselves and against a state-of-the-art method. Of the three, the PSO shows particularly promising results and is comparable to published tools, even at this exploratory stage. Thus, we foresee great improvements if alternative definitions of distance and velocity in a tree space, capable of better handling such non-Euclidean search spaces, are devised in future works. Full article
(This article belongs to the Special Issue Algorithms for Natural Computing Models)
Show Figures

Figure 1

25 pages, 477 KiB  
Article
Mind the O˜: Asymptotically Better, but Still Impractical, Quantum Distributed Algorithms
by Phillip Kerger, David E. Bernal Neira, Zoe Gonzalez Izquierdo and Eleanor G. Rieffel
Algorithms 2023, 16(7), 332; https://doi.org/10.3390/a16070332 - 11 Jul 2023
Cited by 3 | Viewed by 1424
Abstract
We present two algorithms in the quantum CONGEST-CLIQUE model of distributed computation that succeed with high probability: one for producing an approximately optimal Steiner tree, and one for producing an exact directed minimum spanning tree, each of which uses [...] Read more.
We present two algorithms in the quantum CONGEST-CLIQUE model of distributed computation that succeed with high probability: one for producing an approximately optimal Steiner tree, and one for producing an exact directed minimum spanning tree, each of which uses O˜(n1/4) rounds of communication and O˜(n9/4) messages, achieving a lower asymptotic round and message complexity than any known algorithms in the classical CONGEST-CLIQUE model. At a high level, we achieve these results by combining classical algorithmic frameworks with quantum subroutines. Additionally, we characterize the constants and logarithmic factors involved in our algorithms as well as related classical algorithms, otherwise obscured by O˜ notation, revealing that advances are needed to render both the quantum and classical algorithms practical. Full article
(This article belongs to the Collection Feature Paper in Algorithms and Complexity Theory)
20 pages, 4854 KiB  
Article
Mathematical Model of Fuse Effect Initiation in Fiber Core
by Victoria A. Starikova, Yuri A. Konin, Alexandra Yu. Petukhova, Svetlana S. Aleshkina, Andrey A. Petrov and Anatolii V. Perminov
Algorithms 2023, 16(7), 331; https://doi.org/10.3390/a16070331 - 11 Jul 2023
Viewed by 1475
Abstract
This work focuses on the methods of creating in-fiber devices, such as sensors, filters, and scatterers, using the fiber fuse effect. The effect allows for the creation of structures in a fiber core. However, it is necessary to know exactly how this process [...] Read more.
This work focuses on the methods of creating in-fiber devices, such as sensors, filters, and scatterers, using the fiber fuse effect. The effect allows for the creation of structures in a fiber core. However, it is necessary to know exactly how this process works, when the plasma spark occurs, what size it reaches, and how it depends on external parameters such as power and wavelength of radiation. Thus, this present study aims to create the possibility of predicting the consequences of optical breakdown. This paper describes a mathematical model of the optical breakdown initiation in a fiber core based on the thermal conductivity equation. The breakdown generates a plasma spark, which subsequently moves along the fiber. The problem is solved in the axisymmetric formulation. The computational domain consists of four elements with different thermophysical properties at the boundaries of which conjugation conditions are fulfilled. The term describing the heat source in the model is determined by the wavelength of radiation and the refractive indices of the core and the shell and also includes the radiation absorption on the released electrons during the thermal ionization of the quartz glass. The temperature field distributions in the optical fiber are obtained. Based on the calculations, it is possible to estimate the occurrence times of various phase states inside the fiber, in particular, the plasma spark occurrence time. Full article
(This article belongs to the Special Issue Algorithms and Calculations in Fiber Optics and Photonics)
Show Figures

Figure 1

20 pages, 5913 KiB  
Article
A Bioinformatics Analysis of Ovarian Cancer Data Using Machine Learning
by Vincent Schilling, Peter Beyerlein and Jeremy Chien
Algorithms 2023, 16(7), 330; https://doi.org/10.3390/a16070330 - 11 Jul 2023
Cited by 1 | Viewed by 2270
Abstract
The identification of biomarkers is crucial for cancer diagnosis, understanding the underlying biological mechanisms, and developing targeted therapies. In this study, we propose a machine learning approach to predict ovarian cancer patients’ outcomes and platinum resistance status using publicly available gene expression data. [...] Read more.
The identification of biomarkers is crucial for cancer diagnosis, understanding the underlying biological mechanisms, and developing targeted therapies. In this study, we propose a machine learning approach to predict ovarian cancer patients’ outcomes and platinum resistance status using publicly available gene expression data. Six classical machine-learning algorithms are compared on their predictive performance. Those with the highest score are analyzed by their feature importance using the SHAP algorithm. We were able to select multiple genes that correlated with the outcome and platinum resistance status of the patients and validated those using Kaplan–Meier plots. In comparison to similar approaches, the performance of the models was higher, and different genes using feature importance analysis were identified. The most promising identified genes that could be used as biomarkers are TMEFF2, ACSM3, SLC4A1, and ALDH4A1. Full article
(This article belongs to the Special Issue Machine Learning Algorithms for Bioinformatics Problems)
Show Figures

Figure 1

21 pages, 817 KiB  
Article
A Tool for Control Research Using Evolutionary Algorithm That Generates Controllers with a Pre-Specified Morphology
by Francisco-David Hernandez, Domingo Cortes, Marco Antonio Ramirez-Salinas and Luis Alfonso Villa-Vargas
Algorithms 2023, 16(7), 329; https://doi.org/10.3390/a16070329 - 8 Jul 2023
Viewed by 1020
Abstract
In control research and design it is frequently necessary to explore, evaluate, tune and compare many control strategies. These activities are assisted by software tools of increasing complexity; however, even with the existing high performance tools these activities are very time consuming due [...] Read more.
In control research and design it is frequently necessary to explore, evaluate, tune and compare many control strategies. These activities are assisted by software tools of increasing complexity; however, even with the existing high performance tools these activities are very time consuming due to they imply hundred if not thousand of simulations. If the process of doing such simulations is not automated it can be a very time consuming task. There has been proposed evolutionary algorithms (EA) that in the search for an optimal control automatically generate many control structures. However, the space of possible controllers for any dynamical system is huge. Hence it is mandatory to restrict the search space. The best way to restrict the controller search space is to let the designer influence the search direction. In this paper we propose a software tool for control research that has as its main part an EA that produce only controllers having a pre-specified morphology. By specifying a controller morphology the designer can influence the search direction without losing the exploration capability of evolutionary algorithms. The EA is endowed with a cost function tailored for fast evaluation of closed-loop controller performance. The use of the tool is illustrated by searching an sliding mode and similar controllers for an unstable linear and two nonlinear systems. Full article
Show Figures

Figure 1

24 pages, 604 KiB  
Article
ω-Circulant Matrices: A Selection of Modern Applications from Preconditioning of Approximated PDEs to Subdivision Schemes
by Rafael Díaz Fuentes, Stefano Serra-Capizzano and Rosita Luisa Sormani
Algorithms 2023, 16(7), 328; https://doi.org/10.3390/a16070328 - 8 Jul 2023
Cited by 1 | Viewed by 1400
Abstract
It is well known that ω-circulant matrices with ω0 can be simultaneously diagonalized by a transform matrix, which can be factored as the product of a diagonal matrix, depending on ω, and of the unitary matrix Fn associated [...] Read more.
It is well known that ω-circulant matrices with ω0 can be simultaneously diagonalized by a transform matrix, which can be factored as the product of a diagonal matrix, depending on ω, and of the unitary matrix Fn associated to the Fast Fourier Transform. Hence, all the sets of ω-circulants form algebras whose computational power, in terms of complexity, is the same as the classical circulants with ω=1. However, stability is a delicate issue, since the condition number of the transform is equal to that of the diagonal part, tending to max{|ω|,|ω|1}. For ω=0, the set of related matrices is still an algebra, which is the algebra of lower triangular matrices, but they do not admit a common transform since most of them (all except the multiples of the identity) are non-diagonalizable. In the present work, we review two modern applications, ranging from parallel computing in preconditioning of PDE approximations to algorithms for subdivision schemes, and we emphasize the role of such algebra. For the two problems, few numerical tests are conducted and critically discussed and the related conclusions are drawn. Full article
Show Figures

Figure 1

3 pages, 164 KiB  
Editorial
Special Issue “AI for Cybersecurity: Robust Models for Authentication, Threat and Anomaly Detection”
by Francesco Bergadano and Giorgio Giacinto
Algorithms 2023, 16(7), 327; https://doi.org/10.3390/a16070327 - 7 Jul 2023
Viewed by 1591
Abstract
Cybersecurity models include provisions for legitimate user and agent authentication, as well as algorithms for detecting external threats, such as intruders and malicious software [...] Full article
12 pages, 2788 KiB  
Article
Vessel Velocity Estimation and Docking Analysis: A Computer Vision Approach
by João V. R. de Andrade, Bruno J. T. Fernandes, André R. L. C. Izídio, Nilson M. da Silva Filho and Francisco Cruz
Algorithms 2023, 16(7), 326; https://doi.org/10.3390/a16070326 - 30 Jun 2023
Cited by 1 | Viewed by 1428
Abstract
The opportunities for leveraging technology to enhance the efficiency of vessel port activities are vast. Applying video analytics to model and optimize certain processes offers a remarkable way to improve overall operations. Within the realm of vessel port activities, two crucial processes are [...] Read more.
The opportunities for leveraging technology to enhance the efficiency of vessel port activities are vast. Applying video analytics to model and optimize certain processes offers a remarkable way to improve overall operations. Within the realm of vessel port activities, two crucial processes are vessel approximation and the docking process. This work specifically focuses on developing a vessel velocity estimation model and a docking mooring analytical system using a computer vision approach. The study introduces algorithms for speed estimation and mooring bitt detection, leveraging techniques such as the Structural Similarity Index (SSIM) for precise image comparison. The obtained results highlight the effectiveness of the proposed algorithms, demonstrating satisfactory speed estimation capabilities and successful identification of tied cables on the mooring bitts. These advancements pave the way for enhanced safety and efficiency in vessel docking procedures. However, further research and improvements are necessary to address challenges related to occlusions and illumination variations and explore additional techniques to enhance the models’ performance and applicability in real-world scenarios. Full article
(This article belongs to the Special Issue Recent Advances in Algorithms for Computer Vision Applications)
Show Figures

Figure 1

Previous Issue
Next Issue
Back to TopTop