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Article
Publication date: 9 July 2018

Changjin Xu and Peiluan Li

The purpose of this paper is to investigate the existence and global exponential stability of periodic solution of memristor-based recurrent neural networks with time-varying…

143

Abstract

Purpose

The purpose of this paper is to investigate the existence and global exponential stability of periodic solution of memristor-based recurrent neural networks with time-varying delays and leakage delays.

Design/methodology/approach

The differential inequality theory and some novel mathematical analysis techniques are applied.

Findings

A set of sufficient conditions which guarantee the existence and global exponential stability of periodic solution of involved model is derived.

Practical implications

It plays an important role in designing the neural networks.

Originality/value

The obtained results of this paper are new and complement some previous studies. The innovation of this paper concludes two aspects: the analysis on the existence and global exponential stability of periodic solution of memristor-based recurrent neural networks with time-varying delays and leakage delays is first proposed; and it is first time to establish the sufficient criterion which ensures the existence and global exponential stability of periodic solution of memristor-based recurrent neural networks with time-varying delays and leakage delays.

Details

International Journal of Intelligent Computing and Cybernetics, vol. 11 no. 3
Type: Research Article
ISSN: 1756-378X

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Article
Publication date: 1 July 2000

Gavril Acalugaritei

Acalugaritei networks (ANs) are multidimensional evolutionary hierarchical networks. They are called hierarchical because the sets and subsets of components correspond to…

90

Abstract

Acalugaritei networks (ANs) are multidimensional evolutionary hierarchical networks. They are called hierarchical because the sets and subsets of components correspond to different ranks (levels), where: the set of “inferior” rank is the subset of rank zero (j = 0) of the set of immediately “superior” rank. The sets and subsets of components will be noted Sij, where: i is the rank number of the set (i = 0,1,2,3); jis the rank number of the subset within the same set (j = 0,1,2, …, n). We will thus distinguish: \curr Sij=(S0jS1jS2jS3j). They are called evolutionary because the most comprehensive set of components is the set of evolutionary relations. They are called multidimensional because the components of the same rank can be classified according to n dimensions (n criteria: ki where: i = 0, 1, 2,…, n). ANs are of different ranks (ANsi, where: i = 0, 1, 2,…,n). In an AN of a certain rank, the set of fundamental components is the set of sequences of ANs of subordinated ranks.

Details

Kybernetes, vol. 29 no. 5/6
Type: Research Article
ISSN: 0368-492X

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Article
Publication date: 1 October 2004

Miguel Lloret‐Climent and Jose Luis Bonnet‐Jerez

Describes issues relevant to multilevel systems and, as a particular case, living systems analysed from the entities point of view. As attributes, behaviours, sub‐systems, etc.…

129

Abstract

Describes issues relevant to multilevel systems and, as a particular case, living systems analysed from the entities point of view. As attributes, behaviours, sub‐systems, etc., entities are primitive terms. For this reason, in examining issues such as the influences between entities, look indirectly at issues referring to different levels in the system. This notion was also extended in considering the environment system and analysing the different relationships between the system and the environment system.

Details

Kybernetes, vol. 33 no. 9/10
Type: Research Article
ISSN: 0368-492X

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Article
Publication date: 7 June 2018

Phongsatorn Saisutjarit and Takaya Inamori

The purpose of this paper is to investigate the time optimal trajectory of the multi-tethered robot (MTR) on a large spinning net structures in microgravity environment.

149

Abstract

Purpose

The purpose of this paper is to investigate the time optimal trajectory of the multi-tethered robot (MTR) on a large spinning net structures in microgravity environment.

Design/methodology/approach

The MTR is a small space robot that uses several tethers attached to the corner-fixed satellites of a spinning net platform. The transition of the MTR from a start point to any arbitrary designated points on the platform surface can be achieved by controlling the tethers’ length and tension simultaneously. Numerical analysis of trajectory optimization problem for the MTR is implemented using the pseudospectral (PS) method.

Findings

The globally time optimal trajectory for MTR on a free-end spinning net platform can be obtained through the PS method.

Research limitations/implications

The analysis in this paper is limited to a planar trajectory and the effects caused by attitude of the MTR will be neglected. To make the problem simple and to see the feasibility in the general case, in this paper, it is assumed there are no any limitations of mechanical hardware constraints such as the velocity limitation of the robot and tether length changing constraint, while only geometrical constraints are considered.

Practical implications

The optimal solution derived from numerical analysis can be used for a path planning, guidance and navigation control. This method can be used for more efficient on-orbit autonomous self-assembly system or extravehicular activities supports which using a tether-controlled robot.

Originality/value

This approach for a locomotion mechanism has the capability to solve problems of conventional crawling type robots on a loose net in microgravity.

Details

Aircraft Engineering and Aerospace Technology, vol. 90 no. 5
Type: Research Article
ISSN: 1748-8842

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Article
Publication date: 1 September 1995

Norio Watanabe and Shusaku Hiraki

Considers a multi‐stage multi‐product production, inventory andtransportation system including lot production processes and develops amathematical model for a pull type ordering…

567

Abstract

Considers a multi‐stage multi‐product production, inventory and transportation system including lot production processes and develops a mathematical model for a pull type ordering system. The decision variables of the presented model are initial ordering quantities and the objective is to minimize the sum of the replenishment level at each inventory point. The model is formulated as an integer programming problem, and an approximate procedure is proposed to obtain a near optimal solution in short time using a mathematical programming package. Finally, shows a numerical example of the model applied to an actual manufacturing system of an automobile parts manufacturer in order to verify the effectiveness of the solution procedure and to clarify the applicability of the modelling approach.

Details

International Journal of Operations & Production Management, vol. 15 no. 9
Type: Research Article
ISSN: 0144-3577

Keywords

Available. Open Access. Open Access
Article
Publication date: 30 June 2010

Hwa-Joong Kim, Eun-Kyung Yu, Kwang-Tae Kim and Tae-Seung Kim

Dynamic lot sizing is the problem of determining the quantity and timing of ordering items while satisfying the demand over a finite planning horizon. This paper considers the…

193

Abstract

Dynamic lot sizing is the problem of determining the quantity and timing of ordering items while satisfying the demand over a finite planning horizon. This paper considers the problem with two practical considerations: minimum order size and lost sales. The minimum order size is the minimum amount of items that should be purchased and lost sales involve situations in which sales are lost because items are not on hand or when it becomes more economical to lose the sale rather than making the sale. The objective is to minimize the costs of ordering, item , inventory holding and lost sale over the planning horizon. To solve the problem, we suggest a heuristic algorithm by considering trade-offs between cost factors. Computational experiments on randomly generated test instances show that the algorithm quickly obtains near-optimal solutions.

Details

Journal of International Logistics and Trade, vol. 8 no. 1
Type: Research Article
ISSN: 1738-2122

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Article
Publication date: 5 February 2025

Essaid Aourir and Hojatollah Laeli Dastjerdi

This contribution investigates the numerical solution of Volterra integral equations with auto-convolution of the third kind (AVIE). The numerical method applied in this…

6

Abstract

Purpose

This contribution investigates the numerical solution of Volterra integral equations with auto-convolution of the third kind (AVIE). The numerical method applied in this investigation employs a collocation method based on the moving least squares (MLS) approximation. The MLS approximation is an effective way of approximating an unknown function by taking a disordered dataset. This method is a mesh-free approach since it does not require background interpolation or approximation cells, and is independent of domain geometry. The proposed method reduces the solution of third-kind AVIEs to the solution of systems of algebraic equations. By employing the Gauss–Legendre integration formula, we can estimate all the integrals of these equations. The applicability and validity of this method are demonstrated by numerical experiments, and its efficiency and robustness are proven by comparison with existing methods.

Design/methodology/approach

The numerical method applied in this study uses a collocation method based on moving least squares (MLS) approximation. This method is a mesh-free approach since it requires no background interpolation or approximation cells and is independent of domain geometry. Using the Gauss–Legendre integration formula, we can estimate all the integrals of these equations.

Findings

The authors declare that they have no known competing financial interests.

Originality/value

The manuscript has not been copyrighted or published previously and is not under consideration for publication elsewhere.

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Article
Publication date: 3 February 2025

Yifan Wang, Ryuichi Tani and Kenetsu Uchida

In the field of engineering, the fractional moments of random variables play a crucial role and are widely utilized. They are applied in various areas such as structural…

7

Abstract

Purpose

In the field of engineering, the fractional moments of random variables play a crucial role and are widely utilized. They are applied in various areas such as structural reliability assessment and analysis, studying the response characteristics of random vibration systems and optimizing signal processing and control systems. This study focuses on calculating the fractional moments of positive random variables encountered in engineering. This study focuses on calculating the fractional moments of positive random variables encountered in engineering.

Design/methodology/approach

By integrating Laplace transforms with fractional derivatives, both analytical and practical numerical solutions are derived. Furthermore, specific practical application methods are provided.

Findings

This approach allows for the stable and highly accurate calculation of fractional moments based on the integer moments of random variables. Data experiments included in this study demonstrate the effectiveness of this method in solving fractional moment calculations in engineering. Compared to traditional methods, the proposed method offers significant advantages in stability and accuracy, which can further advance research in the engineering field that employs fractional moments.

Originality/value

(1) Accuracy: Although the proposed method does involve some error, its error level is significantly lower than traditional methods, such as the Taylor expansion method. (2) Stability: The computational error of the proposed method is not only minimal but also remains stable within a narrow range as the fractional order varies. (3) Efficiency: Compared to the widely used Taylor expansion method, the proposed method requires only a minimal number of integer-order moments to achieve the desired results. Additionally, it avoids convergence issues during computation, greatly reducing computational resource requirements. (4) Simplicity: The application steps of the proposed method are very straightforward, offering significant advantages in practical applications.

Details

Engineering Computations, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0264-4401

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Article
Publication date: 20 February 2025

Nikolaos Galanos, Evangelos Papoutsis-Kiachagias and Kyriakos Giannakoglou

This paper aims to present a topology optimization (TopO) method for designing heat exchangers (HEx) with two working fluids to be kept apart. The introduction of cut–cells gives…

2

Abstract

Purpose

This paper aims to present a topology optimization (TopO) method for designing heat exchangers (HEx) with two working fluids to be kept apart. The introduction of cut–cells gives rise to the cut-cell TopO method, which computes the optimal distribution of an artificial impermeability field and successfully overcomes the weaknesses of the standard density-based TopO (denTopO) by computing the fluid–solid interface (FSI) at each cycle. This allows to accurately solve the flow and conjugate heat transfer (CHT) problem by imposing exact boundary conditions on the computed FSI and results to correct performances computed without the need to re-evaluate the optimized solutions on a body-fitted grid.

Design/methodology/approach

The elements of an artificial impermeability distribution field defined on a background grid act as the design variables and allow topological changes to take place. Post-processing them yields two fields indicating the location of the two flow streams inside the HEx. At each TopO cycle, the FSIs computed based on these two fields are used as the cutting surfaces of the cut-cell grid. On the so-computed grid, the incompressible Navier–Stokes equations, coupled with the Spalart–Allmaras turbulence model, and the temperature equation are solved. The derivatives of the objective and constraint functions with respect to the design variables of TopO are computed by the continuous adjoint method, using consistent discretization schemes devised thanks to the “Think Discrete – Do Continuous” (TDDC) adjoint methodology.

Findings

The effectiveness of the cut-cell–based TopO method for designing HEx is demonstrated in 2D parallel/counter flow and 3D counter flow HEx operating under both laminar and turbulent flow conditions. Compared to the standard denTopO, its ability to compute FSIs along which accurate boundary conditions are imposed, increases the accuracy of the flow solver, which usually leads to optimal, rather than sub-optimal, solutions that truly satisfy the imposed constraints.

Originality/value

This work proposes a new/complete methodology for the TopO of two-fluid systems including CHT that relies on the cut-cell method. This successfully combines aspects from both TopO and Shape Optimization (ShpO) in a single framework thus overcoming the well-known downsides of standard denTopO regarding its accuracy or the need for a follow-up ShpO after TopO. Instead of adding the well-known Brinkman penalization terms into the flow equations, it computes the FSIs at each optimization cycle allowing the solution of the CHT problem on a cut-cell grid.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 28 January 2025

Xuan Yang, Hao Luo, Xinyao Nie and Xiangtianrui Kong

Tacit knowledge in frontline operations is primarily reflected in the holders’ intuition about dynamic systems. Despite the implicit nature of tacit knowledge, the understanding…

11

Abstract

Purpose

Tacit knowledge in frontline operations is primarily reflected in the holders’ intuition about dynamic systems. Despite the implicit nature of tacit knowledge, the understanding of complex systems it encapsulates can be displayed through formalization methods. This study seeks to develop a methodology for formalizing tacit knowledge in a dynamic delivery system.

Design/methodology/approach

This study employs a structured survey to gather experiential knowledge from dispatchers engaged in last-mile delivery operations. This knowledge is then formalized using a value function approximation approach, which transforms tacit insights into structured inputs for dynamic decision-making. We apply this methodology to optimize delivery operations in an online-to-offline pharmacy context.

Findings

The raw system feature data are not strongly correlated with the system’s development trends, making them ineffective for guiding dynamic decision-making. However, the system features obtained through preprocessing the raw data increase the predictiveness of dynamic decisions and improve the overall effectiveness of decision-making in delivery operations.

Research limitations/implications

This research provides a foundational framework for studying sequential dynamic decision problems, highlighting the potential for improved decision quality and system optimization through the formalization and integration of tacit knowledge.

Practical implications

This approach proposed in this study offers a method to preserve and formalize critical operational expertise. By embedding tacit knowledge into decision-making systems, organizations can enhance real-time responsiveness and reduce operational costs.

Originality/value

This study presents a novel approach to integrating tacit knowledge into dynamic decision-making frameworks, demonstrated in a real-world last-mile delivery context. Unlike previous research that focuses primarily on explicit data-driven methods, our approach leverages the implicit, experience-based insights of operational staff, leading to more informed and effective decision-making strategies.

Details

Industrial Management & Data Systems, vol. ahead-of-print no. ahead-of-print
Type: Research Article
ISSN: 0263-5577

Keywords

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