Auguste Bourgois, A. Chaabouni, A. Rauh, L. Jaulin
In this paper, we propose to study the stability of a navigation method that allows a robot to move in an unstructured environment without compass by measuring a scalar function φ which only depends on the position. The principle is to ask the robot to roll along an isovalue of φ . Using an interval method, we prove the stability of our closed loop system in the special case where φ is linear.
{"title":"Proving the Stability of the Rolling Navigation","authors":"Auguste Bourgois, A. Chaabouni, A. Rauh, L. Jaulin","doi":"10.14232/actacyb.295941","DOIUrl":"https://doi.org/10.14232/actacyb.295941","url":null,"abstract":"In this paper, we propose to study the stability of a navigation method that allows a robot to move in an unstructured environment without compass by measuring a scalar function φ which only depends on the position. The principle is to ask the robot to roll along an isovalue of φ . Using an interval method, we prove the stability of our closed loop system in the special case where φ is linear.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"14 4 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2023-02-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115717273","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In recent years, fractional differential equations have received a significant increase in their use for modeling a wide range of engineering applications. In such cases, they are mostly employed to represent non-standard dynamics that involve long-term memory effects or to represent the dynamics of system models that are identified from measured frequency response data in which magnitude and phase variations are observed that could be captured either by low-order fractional models or high-order rational ones. Fractional models arise also when synthesizing CRONE (Commande Robuste d'Ordre Non Entier) and/or fractional PID controllers for rational or fractional systems. In all these applications, it is frequently required to transform the frequency domain representation into time domain. When doing so, it is necessary to carefully address the issue of the initialization of the pseudo state variables of the time domain system model. This issue is discussed in this article for the reinitialization of fractional integrators which arises among others when solving state estimation tasks for continuous-time systems with discrete-time measurements. To quantify the arising time-domain truncation errors due to integrator resets, a novel interval observer-based approach is presented and, finally, visualized for a simplified battery model.
{"title":"Quantification of Time-Domain Truncation Errors for the Reinitialization of Fractional Integrators","authors":"A. Rauh, R. Malti","doi":"10.14232/actacyb.296010","DOIUrl":"https://doi.org/10.14232/actacyb.296010","url":null,"abstract":"In recent years, fractional differential equations have received a significant increase in their use for modeling a wide range of engineering applications. In such cases, they are mostly employed to represent non-standard dynamics that involve long-term memory effects or to represent the dynamics of system models that are identified from measured frequency response data in which magnitude and phase variations are observed that could be captured either by low-order fractional models or high-order rational ones. Fractional models arise also when synthesizing CRONE (Commande Robuste d'Ordre Non Entier) and/or fractional PID controllers for rational or fractional systems. In all these applications, it is frequently required to transform the frequency domain representation into time domain. When doing so, it is necessary to carefully address the issue of the initialization of the pseudo state variables of the time domain system model. This issue is discussed in this article for the reinitialization of fractional integrators which arises among others when solving state estimation tasks for continuous-time systems with discrete-time measurements. To quantify the arising time-domain truncation errors due to integrator resets, a novel interval observer-based approach is presented and, finally, visualized for a simplified battery model.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123768691","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We consider the numerical construction of inverses for a class of rational functions. We propose two inverse algorithms, which can be used to simultaneously identify every zero of a rational function or polynomial. In the first case, we propose a generalization of an inverse algorithm based on our previous work and specify a class of rational functions, for which this generalized algorithm is applicable. In the second case, we provide a method to construct Blaschke-products, whose roots match the roots of a polynomial or a rational function. We also consider different iterative methods to numerically calculate the inverse points and discuss their properties.
{"title":"Inverses of Rational Functions","authors":"Tamás Dózsa","doi":"10.14232/actacyb.294975","DOIUrl":"https://doi.org/10.14232/actacyb.294975","url":null,"abstract":"We consider the numerical construction of inverses for a class of rational functions. We propose two inverse algorithms, which can be used to simultaneously identify every zero of a rational function or polynomial. In the first case, we propose a generalization of an inverse algorithm based on our previous work and specify a class of rational functions, for which this generalized algorithm is applicable. In the second case, we provide a method to construct Blaschke-products, whose roots match the roots of a polynomial or a rational function. We also consider different iterative methods to numerically calculate the inverse points and discuss their properties.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"18 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-10-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115347987","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper is concerned with a dynamic inventory control system described by a network model where the nodes are warehouses and the arcs represent production and distribution activities. We assume that an uncertain demand may take any value in an assigned interval and we allow that the system is disturbed by noise inputs. These assumptions yield a model with a mix of interval and stochastic demand uncertainties. We use the method of model predictive control to derive the control strategy. To deal with interval uncertainty we use the interval analysis tools and act according to the interval analysis theory. The developed results are illustrated using a numerical example.
{"title":"The Inventory Control Problem for a Supply Chain With a Mixed Type of Demand Uncertainty","authors":"E. Chausova","doi":"10.14232/actacyb.295044","DOIUrl":"https://doi.org/10.14232/actacyb.295044","url":null,"abstract":"This paper is concerned with a dynamic inventory control system described by a network model where the nodes are warehouses and the arcs represent production and distribution activities. We assume that an uncertain demand may take any value in an assigned interval and we allow that the system is disturbed by noise inputs. These assumptions yield a model with a mix of interval and stochastic demand uncertainties. We use the method of model predictive control to derive the control strategy. To deal with interval uncertainty we use the interval analysis tools and act according to the interval analysis theory. The developed results are illustrated using a numerical example.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"45 5 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126120535","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper deals with convergence theorems of the Galerkin finite element approximation for the second-order elliptic boundary value problems. Under some quite general settings, we show not only the pointwise convergence but also prove that the norm of approximate operator converges to the corresponding norm for the inverse of a linear elliptic operator. Since the approximate norm estimates of linearized inverse operator play an essential role in the numerical verification method of solutions for non-linear elliptic problems, our result is also important in terms of guaranteeing its validity. Furthermore, the present method can also be applied to more general elliptic problems, e.g., biharmonic problems and so on.
{"title":"On Some Convergence Properties for Finite Element Approximations to the Inverse of Linear Elliptic Operators","authors":"T. Kinoshita, Yoshitaka Watanabe, M. Nakao","doi":"10.14232/actacyb.294906","DOIUrl":"https://doi.org/10.14232/actacyb.294906","url":null,"abstract":"This paper deals with convergence theorems of the Galerkin finite element approximation for the second-order elliptic boundary value problems. Under some quite general settings, we show not only the pointwise convergence but also prove that the norm of approximate operator converges to the corresponding norm for the inverse of a linear elliptic operator. Since the approximate norm estimates of linearized inverse operator play an essential role in the numerical verification method of solutions for non-linear elliptic problems, our result is also important in terms of guaranteeing its validity. Furthermore, the present method can also be applied to more general elliptic problems, e.g., biharmonic problems and so on.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"108 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-09-02","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123534027","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Type parametrization is an essential construct in modern programming languages. On one hand, Java offers generics, on the other hand, C++ offers templates for highly reusable code. The mechanism between these constructs differs and affects usage and runtime performance, as well. Java uses type erasure, C++ deals with instantiations.In this paper, we argue for an approach in Java which is similar to C++ template construct. We evaluate the runtime performance of instantiated code and we present our tool which is able to use Java generics as templates. This tool generates Java source code. We present how this approach improves the usage of Java generics.
{"title":"Instantiation of Java Generics","authors":"Péter Soha, Norbert Pataki","doi":"10.14232/actacyb.284073","DOIUrl":"https://doi.org/10.14232/actacyb.284073","url":null,"abstract":"Type parametrization is an essential construct in modern programming languages. On one hand, Java offers generics, on the other hand, C++ offers templates for highly reusable code. The mechanism between these constructs differs and affects usage and runtime performance, as well. Java uses type erasure, C++ deals with instantiations.In this paper, we argue for an approach in Java which is similar to C++ template construct. We evaluate the runtime performance of instantiated code and we present our tool which is able to use Java generics as templates. This tool generates Java source code. We present how this approach improves the usage of Java generics.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"22 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-21","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"126333166","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Affine iterations of the form xn+1=Axn+b converge, using real arithmetic, if the spectral radius of the matrix A is less than 1. However, substituting interval arithmetic to real arithmetic may lead to divergence of these iterations, in particular if the spectral radius of the absolute value of A is greater than 1. We will review different approaches to limit the overestimation of the iterates, when the components of the initial vector x(0) and b are intervals. We will compare, both theoretically and experimentally, the widths of the iterates computed by these different methods: the naive iteration, methods based on the QR- and SVD-factorization of A, and Lohner's QR-factorization method. The method based on the SVD-factorization is computationally less demanding and gives good results when the matrix is poorly scaled, it is superseded either by the naive iteration or by Lohner's method otherwise.
{"title":"Affine Iterations and Wrapping Effect: Various Approaches","authors":"N. Revol","doi":"10.14232/actacyb.295251","DOIUrl":"https://doi.org/10.14232/actacyb.295251","url":null,"abstract":"Affine iterations of the form xn+1=Axn+b converge, using real arithmetic, if the spectral radius of the matrix A is less than 1. However, substituting interval arithmetic to real arithmetic may lead to divergence of these iterations, in particular if the spectral radius of the absolute value of A is greater than 1. We will review different approaches to limit the overestimation of the iterates, when the components of the initial vector x(0) and b are intervals. We will compare, both theoretically and experimentally, the widths of the iterates computed by these different methods: the naive iteration, methods based on the QR- and SVD-factorization of A, and Lohner's QR-factorization method. The method based on the SVD-factorization is computationally less demanding and gives good results when the matrix is poorly scaled, it is superseded either by the naive iteration or by Lohner's method otherwise.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"7 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2022-01-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125136919","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Since the advent of smartphones, IoT and cloud computing, we have seen an industry-wide requirement to integrate different healthcare applications with each other and with the cloud, connecting multiple institutions or even countries. But despite these trends, the domain of access control and security of sensitive healthcare data still raises a serious challenge for multiple developers and lacks the necessary definitions to create a general security framework addressing these issues. Taking into account newer, more special cases, such as the popular heterogeneous infrastructures with a combination of public and private clouds, fog computing, Internet of Things, the area becomes more and more complicated. In this paper we will introduce a categorization of these required policies, describe an infrastructure as a possible solution to these security challenges, and finally evaluate it with a set of policies based on real-world requirements.
{"title":"Access Control of EHR Records in a Heterogeneous Cloud Infrastructure","authors":"Zoltán Szabó, Vilmos Bilicki","doi":"10.14232/actacyb.290283","DOIUrl":"https://doi.org/10.14232/actacyb.290283","url":null,"abstract":"Since the advent of smartphones, IoT and cloud computing, we have seen an industry-wide requirement to integrate different healthcare applications with each other and with the cloud, connecting multiple institutions or even countries. But despite these trends, the domain of access control and security of sensitive healthcare data still raises a serious challenge for multiple developers and lacks the necessary definitions to create a general security framework addressing these issues. Taking into account newer, more special cases, such as the popular heterogeneous infrastructures with a combination of public and private clouds, fog computing, Internet of Things, the area becomes more and more complicated. In this paper we will introduce a categorization of these required policies, describe an infrastructure as a possible solution to these security challenges, and finally evaluate it with a set of policies based on real-world requirements.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"323 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121245170","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Atomicity, consistency, isolation and durability are essential properties of many distributed systems. They are often abbreviated as the ACID properties. Ensuring ACID comes with a price: it requires extra computing and network capacity to ensure that the atomic operations are done perfectly, or they are rolled back. When we have higher requirements on performance, we need to give up the ACID properties entirely or settle for eventual consistency. Since the ambiguity of the order of the events, such algorithms can get very complicated since they have to be prepared for any possible contingencies. Traquest model is an attempt for creating a general concurrency model that can bring the ACID properties without sacrificing a too significant amount of performance.
{"title":"Traquest Model: A Novel Model for ACID Concurrent Computations","authors":"D. B. Rátai, Zoltán Horváth, Z. Porkoláb, M. Tóth","doi":"10.14232/actacyb.288765","DOIUrl":"https://doi.org/10.14232/actacyb.288765","url":null,"abstract":"Atomicity, consistency, isolation and durability are essential properties of many distributed systems. They are often abbreviated as the ACID properties. Ensuring ACID comes with a price: it requires extra computing and network capacity to ensure that the atomic operations are done perfectly, or they are rolled back. \u0000When we have higher requirements on performance, we need to give up the ACID properties entirely or settle for eventual consistency. Since the ambiguity of the order of the events, such algorithms can get very complicated since they have to be prepared for any possible contingencies. Traquest model is an attempt for creating a general concurrency model that can bring the ACID properties without sacrificing a too significant amount of performance.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"297 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"134213776","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Supervised machine learning tasks often require a large number of labeled training data to set up a model, and then prediction - for example the classification - is carried out based on this model. Nowadays tremendous amount of data is available on the web or in data warehouses, although only a portion of those data is annotated and the labeling process can be tedious, expensive and time consuming. Active learning tries to overcome this problem by reducing the labeling cost through allowing the learning system to iteratively select the data from which it learns. In special case of active learning, the process starts from zero initialized scenario, where the labeled training dataset is empty, and therefore only unsupervised methods can be performed. In this paper a novel query strategy framework is presented for this problem, called Clustering Based Balanced Sampling Framework (CBBSF), which is not only select the initial labeled training dataset, but uniformly selects the items among the categories to get a balanced labeled training dataset. The framework includes an assignment technique to implicitly determine the class membership probabilities. Assignment solution is updated during CBBSF iterations, hence it simulates supervised machine learning more accurately as the process progresses. The proposed Spectral Clustering Based Sampling (SCBS) query startegy realizes the CBBSF framework, and therefore it is applicable in the special zero initialized situation. This selection approach uses ClusterGAN (Clustering using Generative Adversarial Networks) integrated in the spectral clustering algorithm and then it selects an unlabeled instance depending on the class membership probabilities. Global and local versions of SCBS were developed, furthermore, most confident and minimal entropy measures were calculated, thus four different SCBS variants were examined in total. Experimental evaluation was conducted on the MNIST dataset, and the results showed that SCBS outperforms the state-of-the-art zero initialized active learning query strategies.
监督式机器学习任务通常需要大量标记的训练数据来建立模型，然后根据该模型进行预测(例如分类)。如今，在网络上或数据仓库中有大量的数据，尽管这些数据中只有一部分被注释了，而且标记过程可能是乏味、昂贵和耗时的。主动学习试图克服这个问题，通过允许学习系统迭代地选择学习的数据来减少标记成本。在主动学习的特殊情况下，该过程从零初始化场景开始，其中标记的训练数据集是空的，因此只能执行无监督方法。针对这一问题，本文提出了一种新的查询策略框架——基于聚类的平衡采样框架(CBBSF)，该框架不仅选择初始标记训练数据集，而且在分类中统一选择项目，从而得到一个平衡标记训练数据集。该框架包括一种赋值技术来隐式地确定类隶属概率。分配解决方案在CBBSF迭代期间更新，因此随着过程的进行，它更准确地模拟了监督机器学习。提出的基于谱聚类采样(SCBS)查询策略实现了CBBSF框架，因此适用于特殊的零初始化情况。该方法将ClusterGAN (Clustering using Generative Adversarial Networks)集成到谱聚类算法中，然后根据类隶属度概率选择一个未标记的实例。开发了SCBS的全球和本地版本，此外，计算了最自信和最小熵度量，从而总共检查了四种不同的SCBS变体。在MNIST数据集上进行了实验评估，结果表明SCBS优于最先进的零初始化主动学习查询策略。
{"title":"Zero Initialized Active Learning with Spectral Clustering using Hungarian Method","authors":"Dávid Papp","doi":"10.14232/actacyb.288006","DOIUrl":"https://doi.org/10.14232/actacyb.288006","url":null,"abstract":"Supervised machine learning tasks often require a large number of labeled training data to set up a model, and then prediction - for example the classification - is carried out based on this model. Nowadays tremendous amount of data is available on the web or in data warehouses, although only a portion of those data is annotated and the labeling process can be tedious, expensive and time consuming. Active learning tries to overcome this problem by reducing the labeling cost through allowing the learning system to iteratively select the data from which it learns. In special case of active learning, the process starts from zero initialized scenario, where the labeled training dataset is empty, and therefore only unsupervised methods can be performed. In this paper a novel query strategy framework is presented for this problem, called Clustering Based Balanced Sampling Framework (CBBSF), which is not only select the initial labeled training dataset, but uniformly selects the items among the categories to get a balanced labeled training dataset. The framework includes an assignment technique to implicitly determine the class membership probabilities. Assignment solution is updated during CBBSF iterations, hence it simulates supervised machine learning more accurately as the process progresses. The proposed Spectral Clustering Based Sampling (SCBS) query startegy realizes the CBBSF framework, and therefore it is applicable in the special zero initialized situation. This selection approach uses ClusterGAN (Clustering using Generative Adversarial Networks) integrated in the spectral clustering algorithm and then it selects an unlabeled instance depending on the class membership probabilities. Global and local versions of SCBS were developed, furthermore, most confident and minimal entropy measures were calculated, thus four different SCBS variants were examined in total. Experimental evaluation was conducted on the MNIST dataset, and the results showed that SCBS outperforms the state-of-the-art zero initialized active learning query strategies.","PeriodicalId":187125,"journal":{"name":"Acta Cybern.","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2021-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128239232","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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