A Note on the ‘Round Robin’ Design

The ‘Round Robin’ design was suggested as suitable for screening a group of treatments. But in this design the variances of treatment are very dependent on the relative position of treatments. This detracts from its value as a screening design.     

Comment on ‘Technical Note – Reaching more states for control of FMS’

Uzam and Zhou (Uzam, M. and Zhou, M., 2006. An improved iterative synthesis method for liveness enforcing supervisors of flexible manufacturing systems. International Journal of Production Research, 44 (10), 1987–2030) were able to obtain a near optimal controlled model for the net S³PR with 21,562 good states. Chao's deadlock recovery scheme (Chao, D.Y., 2010. Technical Note – Reaching more states for control of FMS. International Journal of Production Research, 48 (4), 1217–1220) improves by reaching more states (21,585). However, this paper identifies a problem and proposes a solution.     

Optimization of 2D boundary element models using β-splines and genetic algorithms

The optimization of bidimensional shapes is one of the most commonly addressed problems in engineering. This work is concerned with the use of Genetic Algorithms (GAs) and β-spline-curves modeling for the optimization of Boundary Element Models (BEM). The paper briefly summarizes the basis of the GAs formulation and describes how to use refined genetic operators. The model boundary is discretized by using the BEM, and selected parts of the boundary are modeled by using β-spline curves, in order to allow easy remeshing and adaptation of the boundary to the external actions. Two numerical examples are presented and discussed in detail, showing that the proposed combined technique is able to optimize the shape of the domains with minimum computational effort. The reduction in the model area is significant, without violating the restrictions imposed to the model.     

A technical note on ‘Analysis of closed loop supply chain using genetic algorithm and particle swarm optimisation’

This study analyses the mixed-integer linear program (MILP) proposed by Kannan et al. [Kannan, G., Noorul Hag, A., and Devika, M., 2009. Analysis of closed loop supply chain using genetic algorithm and particle swarm optimization. International Journal of Production Research, 47 (5), 1175–1200] in their paper entitled ‘Analysis of closed loop supply chain using genetic algorithm and particle swarm optimisation’. Since we find inconsistencies in the model, we propose modifications to rectify the flaws. The revised model is presented and tested using a hypothetical problem.     

More on ‘Models and algorithms for the dynamic-demand joint replenishment problem’

This paper presents tight mathematical programming formulations for the dynamic demand joint replenishment problem (DJRP). Experimental studies using general-purpose software document the improved computational efficiency of the new formulations versus the earlier models of Boctor et al. (Boctor, F.F., Laporte, G. and Renaud, J., Models and algorithms for the dynamic-demand joint replenishment problem. Int. J. Prod. Res., 2004, 42, 2667–2678.) and Robinson and Gao (Robinson, E.P. and Gao, L., A dual-ascent procedure for multi-product dynamic demand coordinated replenishment with backlogging. Manag. Sci., 1996, 42, 1556–1564.). The findings encourage the development of specialized algorithms for their solution. The paper also evaluates the performance of the perturbation and dual-ascent heuristics for solving DJRP finding the perturbation heuristic is superior at relatively low set-up cost ratios and high joint set-up cost levels, while the dual-ascent heuristic strongly dominates at relatively high set-up cost ratios and low joint set-up costs. Considering that both heuristics are computationally efficient, the best application strategy is to solve the problem with both heuristics and implement the best found solution.     

Design,physical prototyping and initial characterisation of ‘lockyballs’

Directed tissue self-assembly or bottom-up modular approach in tissue biofabrication is an attractive and potentially superior alternative to a classic top-down solid scaffold-based approach in tissue engineering. For example, rapidly emerging organ printing technology using self-assembling tissue spheroids as building blocks is enabling computer-aided robotic bioprinting of three-dimensional (3D) tissue constructs. However, achieving proper material properties while maintaining desirable geometry and shape of 3D bioprinted tissue engineered constructs using directed tissue self-assembly, is still a challenge. Proponents of directed tissue self-assembly see the solution of this problem in developing methods of accelerated tissue maturation and/or using sacrificial temporal supporting of removable hydrogels. In the meantime, there is a growing consensus that a third strategy based on the integration of a directed tissue self-assembly approach with a conventional solid scaffold-based approach could be a potential optimal solution. We hypothesise that tissue spheroids with ‘velcro®-like’ interlockable solid microscaffolds or simply ‘lockyballs’ could enable the rapid in vivo biofabrication of 3D tissue constructs at desirable material properties and high initial cell density. Recently, biocompatible and biodegradable photo-sensitive biomaterials could be fabricated at nanoscale resolution using two-photon polymerisation (2PP), a development rendering this technique with high potential to fabricate ‘velcro®-like’ interlockable microscaffolds. Here we report design studies, physical prototyping using 2PP and initial functional characterisation of interlockable solid microscaffolds or so-called ‘lockyballs’. 2PP was used as a novel enabling platform technology for rapid bottom-up modular tissue biofabrication of interlockable constructs. The principle of lockable tissue spheroids fabricated using the described lockyballs as solid microscaffolds is characterised by attractive new functionalities such as lockability and tunable material properties of the engineered constructs. It is reasonable to predict that these building blocks create the basis for a development of a clinical in vivo rapid biofabrication approach and form part of recent promising emerging bioprinting technologies.     

Identifying ‘associated-sleeping-beauties’ in ‘swan-groups’ based on small qualified datasets of physics and economics

Scientometrics - ‘Sleeping beauties’ refer to the papers that received no or scarce citation after appearance, but considerable citations several years later, which is a special...     

A note on “Monitoring the ratio of two normal variables using variable sampling interval exponentially weighted moving average control charts”

Considered monitoring of the ratio of two correlated normal random variables based on an approximation. In this note, we derive a closed form expression for the ratio of two correlated normal random variables. We point out that the approximation used in Nguyen et al. does not always perform well.     

Comments on ‘Effect of obstacle strength and spacing on the slope of Haasen plot’

In a recent paper, Mishra et al. [Effect of obstacle strength and spacing on the slope of Haasen plot. Mater Sci Technol. 2019;1–6. doi:10.1080/02670836.2019.1567043], discrepancy between theoretical and experimental results in the slope of the Haasen plot between pure metals and alloys were reported. The discrepancy arises from a common belief that when Haasen plot for pure metals is extended to metals with multiple strengthening mechanisms, the inverse of activation volume components can be linearly superposed. It is conjectured that the slope of the Haasen plot should remain the same for both the pure metals and alloys, as it is governed only by dislocation–dislocation interaction. The purpose of this note is to clarify that the conjecture of invariant Haasen slope is only a special case.     

Joint estimation of E–N curves and their scatter using evolutionary algorithms

We present an approach for estimating E–N curves and their scatter. The scatter of a number of load cycles to failure at an arbitrary amplitude-strain level is modelled using a two-parametric Weibull distribution with the constant shape parameter β and the scale parameter η dependent on the strain amplitude by the Coffin–Manson equation. In this way the E–N curve and its scatter can be described using five parameters: the four parameters of the Coffin–Manson equation for the scale parameter of the Weibull distribution and the shape parameter of the Weibull distribution. The objective was to estimate these five parameters, which are generally unknown (since the data from the literature are manly known only for the median E–N curves), on the basis of the known fatigue-life data to obtain not only the trend of the E–N curve, but also its scatter. In order to estimate these parameters on the basis of the fatigue-life data, two evolutionary algorithms were applied: a real-valued genetic algorithm (GA) and the differential ant-stigmergy algorithm (DASA). In the article a mathematical background of the approach is presented and applied to 27 test cases of simulated fatigue-life data and one real case of experimentally obtained fatigue-life data. The results are analysed and discussed.     

Design of a double microprocessor‐based on‐line process control system

Abstract

A numerical technique for integrating the full Navier‐Stokes and diffusion equations through an initial value problem has been used to investigate the time development of a line buoyant source issuing in a density‐stratified environment. The basic physical features and some structures of the interactions of the motion at the intermediate mixing region are obtained. Results show that the stratification tends to inhibit the flow development of the buoyant source and to encourage the formation of a recirculatory vortex on the lower region near the source and the upper region.     

Process flow industry—scheduling and control using theory of constraints

This paper discusses the applicability of the Theory of Constraints (TOC) in the process flow industry and compares TOC to the current practice. The Drum-Buffer-Rope methodology is altered to meet the needs of the process flow environment. Guidelines for the strategic location of and determination of the reduced WIP inventory levels are provided.     

Literature review on the ‘Smart Factory’ concept using bibliometric tools

The objective of this paper is to depict a landscape of the scientific literature on the concept of the ‘Smart Factory’, which in recent years is gaining more and more attention from academics and practitioners because of significant innovations in the production systems within the manufacturing sector. To achieve this objective, a dynamic methodology called ‘Systematic Literature Network Analysis (SLNA)’ has been applied. This methodology combines the Systematic Literature Review approach with the analysis of bibliographic networks. The adopted methodology allows complementing traditional content-based literature reviews by extracting quantitative information from bibliographic networks to detect emerging topics, and by revealing the dynamic evolution of the scientific production of a discipline. This dynamic analysis allowed highlighting research directions and critical areas for the development of the ‘Smart Factory’. At the same time, it offers insights on the fields on which companies, associations, politicians and technology providers need to focus in order to allow a real transition towards the implementation of large-scale Smart Factory.     

The usage of ‘theory’ and ‘model’ in scientific conceptualization

The results of a survey are reported and interpreted, pertaining to the way scientists use the terms theory and model to conceptualize the scientific information and ideas they deal with. Initially the assessment of the importance of a new theoretical approach in science is done to a large extent on the basis of the conceptual structure of the new approach, but later the predictive power plays an increasingly more important role. It is suggested that results like those in this study might perhaps be used to critically evaluate new theoretical approaches in science even at the time of their conception.     

Development and Prospect on Optimum Design of Metal Forming Process

1.IntroductionThe research of metal forming theoryand technology always takes an importantplace in materials science and engineering.However,in a long period,the developmentof technology goes ahead of the theoreticalstudy.Most design principles used in prac-